led solar project
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Last modified on 20090804
* LED3X Solar Tracker A simple, accurate, low cost, single axis electronic solar tracker based on using green LEDs as photovoltaic light sensors.
Electronic Projects
Last modified on 20090110
Go back to Red Rock Energy.
Actuator Brad's-Trough CDS Sensor Tracker Chace Tracker Charger Charging Temperature Damage Rich DeMartile Diversion1 Efficiency EWB IO LED Solar Trackers MPPT Demoing my Tracker at the MREA Energy Fair New LED3X Solar Tracker NREL Maps Patent5622078 Making PC Boards PWM Relay Tracker Shunt1 Shunt2 Shunt3 Solar Trackers Surface Mount Codebook Terminals Tracker Economics Traxle TriPod Mount Under-voltage.
ewb
Electronics Workbench
I use Electronics Workbench Personal Edition.
This program includes circuit design cad, simulation, and auto routing PC layout. I also use PSPICE at Unisys which has more capabilities but costs 6 times as much and needs to be renewed yearly.
pcb
Making PC Boards
apc
AP CircuitsCanadaPrototype Printed Circuit Board Fabrication Since 1988
twinstar
Twin Star Inc.Excelant 1 day turn around policy for prototype quantities. And their local to me.4"x10" $100 10"x10" $175The cool thing about this offer is there is no limitation on how many individual circuits that can be crammed into the area. I know of no other board maker that will do this.What a deal!
trc
TRC CircuitsThese guys make boards for me when large quantities are needed.
olimex
OLIMEX Ltd.89 Slavjanska St., P.O.Box 237, Plovdiv 4000BulgariaPrinted Circuit Board (PCB) Prototypes
expresspcb
ExpressPCBThey give you a proprietary PC board cad program that allows quick turn around board processing.The program is easy to use if not overly simplistic.Printed Circuit Board (PCB) Prototypes
far
FAR CIRCUITSPrinted Circuit BoardsThy make double sided non plated through service. No email!Custom boards may be made for $.50 square inch or $4.00 minimum per board for single sided, etched, drilled and solder coated.
Custom double sided non-plated through holes, etched, drilled and solder coated boards may be made for $.75 per square inch or $6.00 minimum per board. A clear film negative is required for custom boards. Film from camera ready artwork is $8.00 per shot based on 8" x 10" film per shot. Quantity pricing available. Far Circuits reserves the right to change the pricing based on the complexity of the board.
smd
SMD Codebook
I generally design circuitry that uses surface mount soldering techniques.
This link has a wealth of information about surface mount package shape and connection information.
This program is intended to serve as a guide to the manipulation of data that supports the concepts and methodology for developing surface mount land patterns that are identified in IPC-SM-782, "Surface Mount Design and Land Pattern Standard".
io
8 Bit I/O.
Prototype of an 8 Bit Experimental Bit Serial I/O.
I needed a universal I/O device for my computers. I had several requirements:
1. The ports may need to be as much as 2000 ft from the computer.
2. Ideally the I/O ports need to be easily expandable from the same control output. 3. Speed should be medium. Capable of up to several thousand bytes per second.
With these requirements in mind, and some others, I decided on a variation of National Semiconductors "Micro Wire"(TM). In general this is called a "bit serial" interface. The interface is composed of shift registers connected in series. Each port is in a chain. Data bits are sent down the chain through the shift registers for output. Input data bits are similarly sent down the chain to be inputted into the computer.
My standard bit serial I/O consists of 6 wires. The wires for the standard version use an RJ11-6 6 conductor flat telephone type cable. I also have a simplified 4 wire version. This 4 wire version is predominantly used for output devices only. Pins 5 and 6 are not used. This version eliminates the data input channel and has no self powering capability.
Bit Serial Pin Designations.
Pin # Color Name 6 Blue Interface power 5 Yellow Serial Data Bit In 4 Green Serial Data Bit Out 3 Red Serial Clock 2 Black Data Strobe 1 White Ground
In some cases the printer port can supply all the power needed to run the interface.
IOBit Serial Interface Schematic.
Diagram of RJ11-6 Connector.
RJ11-6 Interface Data Input RJ11-6 Printer Port Adapter RJ11-6 Loop Through Connector -------------------------- --------------------------| ------------------------ | | ------------------------ ||| W B R G Y B || || B Y G R B W |||| h l e r e l || || l e r e l h |||| i a d e l u || || u l e d a i |||| t c e l e || || e l e c t |||| e k n o || || o n k e ||||-- w -- | | -- w -- ||| | 1 2 3 4 5 6 | | | | 6 5 4 3 2 1 | |
| --- --- | | --- --- || | | | | | | || ---------- | | ---------- | -------------------------- -------------------------- View from the Cable side View from the Cable side
Cable to Plug Arrangement.
When choosing or building the cables that connect the computer and I/O boards together make sure they are the strait through type. In
other words the cable has NO TWISTS in it.
________________ 6 Conductor < < ________________| | | Blue 6| Flat Cable > > |6 Blue | | || | | Yellow 5|_______________< <___|5 Yellow | | || | | Green 4| > > |4 Green | | || | | Red 3|_______________< <___|3 Red | | || | | Black 2| No Twists > > |2 Black | | ||_|___|___White_1| < < |1_White___|___|_| > > ______________ 6 Conductor < < ______________ |___| RJ11-6 | Flat Cable > > | RJ11-6 |___| _| PLUG |_______________< <___| PLUG |_|________________|________________> >__|________________| \ \ No Twists < < / / \ \ > > / / \ \ < < / / -- > > --
Connection Diagram. -------------| || Computer || |------+ <-- Parallel Port Adapter ------------- | | ------------- || I/O Board |------+ <-- Interface Data Input| Highest || Addressed |------+ <-- Loop Through Connector ------------- | | ------------- || I/O Board |------+ <-- Interface Data Input| Middle || Addressed |------+ <-- Loop Through Connector ------------- |
| ------------- || I/O Board |------+ <-- Interface Data Input| Lowest || Addressed |XXX <-- Loop Through Connector ------------- ^---------- TerminatorThe Terminator, XXX, is built by connecting the Pin 4 Green and Pin 5 Yellow wires together in an RJ11-6 plug in the last
I/O device in a string.
iooperationBit Serial Sequence of Operation.
1.Put one bit on the data bit out line. 2.Bring the data clock line high and then low. 3.Repeat until all the output data is shifted to the registers. 4.Bring the strobe line high and then low. The strobe line does double duty. It latches the output data into the output registers and drivers. It
also clocks input data into the input shift registers that will be shifted in later. The first input bit is already present on the computer serial data bit input line.
5.Bring the data clock line high and then low. 6. Input each bit in turn. 7.As a check of the output continue to read in a copy of the output bits. 8.As a check of the input reread the input twice.
The software was written in Basic. It directly "Bit Bangs" the printer port.
There are 2 type of registers used in the system.
1. CD4021BC is an 8-stage parallel input/serial output shift register. This register is used for inputs.Fairchild Semiconductor data sheet for the CD4021BCTexas Instruments data sheet for the CD4021B
2. CD4094BC consists of an 8-bit shift register and a 3-State 8-bit latch. This register is used for outputs. Note, I don't use the 3-State feature.Fairchild Semiconductor data sheet for the CD4094BCTexas Instruments data sheet for the CD4094B
Of course the program needs to have copies of the external registers.The faster the computer the faster the data can be transferred.
This picture shows the RJ11-6 glued down. The next revision has the connectors soldered down in the normal surface mounted way.
movers
Satellite Dish Linear Actuator Driver.
Prototype of Bit Serial Quad Satellite Actuator Driver.
I needed to drive satellite dish type actuators for positioning components of my heliostats. I decided to design the interface such that it drives the most common, read cheap, types of these actuators. These generally have either limit switches or overrun clutches to prevent damage to the drive train. Another trait is the use of a single counter switch.
The satellite actuators can draw upwards of 15 Amps when in overrun. This takes a robust transistor. I have chosen 30 Amp P and N channel power MOSFETs in a true high voltage CMOS H bridge configuration. The implementation can drive 4 actuators continuously without overheating, not even warm, not even in hot weather.
The driver consists of an "exclusive or" gate driving the bridge. One input is from the computer software and the other is from the feedback actuator read switch. The job of the exclusive or gate is to apply power to the actuator motor driver until the condition of the feedback switch is the same as the movement bit from the computer. This process allows the computer to move the actuator in small single steps.
The direction the actuator travels is determined by enabling pairs of transistors in the H bridge. One pair for movement outward and the other pair for movement inward.
The computer keeps track of the position and the direction of the last movement. The computer repeatedly sends direction and movement commands to the four drivers. This action causes smooth and even movements to all actuators. The software makes all the actuators move in a manner such that they will all arrive at the required position simultaneously. This in effect makes the rate of movement of the actuators that need to move a small amount less than the actuators that need to move a large amount. My software can drive more than one of these driver boards so any number of actuators may be used. Neat huh!
actuator
I've been compiling some data about the currently available linear actuators. I'm presenting the data here.
I am also working on a simplified driver based on a PIC16C715 micro controller by MicroChip. It will be small and have over current protection.
terminals
Terminals.
Power Transistor Terminals.
The arrows in this picture point to examples of power transistors used as output terminals. The terminals are composed of two power transistors mounted vertically and back to back. Since they dissipate so little power they don't need heat sinks. The machine screw is used to clamp conventional spade terminals between the two transistors.
I use hot melt glue to hold the nut in place.
This picture shows the RJ11-6 telephone wire connection. There is also another RJ11-6 connector on the other end of the board. The second connector is used to connect to other boards. If this board is the last in the string a dummy data turn around jumper, or terminator, is used.
This picture shows the RJ11-6 glued down. The next revision has the connectors soldered down in the normal surface mounted way.
ledtracker
Tracker
theenergydude
* theenergydude's Community Call Gary Carmichael, The Energy Dude, will be interviewing me about solar trackers.We will discuss solar tracking advantages and disadvantages for a number of applications.Hear us Saturday 2009/03/21 01:00 PM EDThttp://www.talkshoe.com/tc/40649
sunpath
Sunpath diagram.
I've been compiling some data about the currently available linear actuators. I'm presenting the data here.
coffee
Solar Coffee Roaster Contest
OK, here's a real challenge. These guys, Dave and Mike Hartkop http://www.solarroast.com , have an unusual Coffee roasting business. They have built their solar powered Helios 4 coffee roaster. Essentially a large Fresnel dish on a vertical axis mount.
Up to now they have been manually controlling this dish. Actually this works pretty good as the operator must be on hand to monitor the roasting anyway. Roasting takes 10 to 20 minutes and needs to be adjusted every 2 to 3 minutes. I don't know if I'd have the patience to do this %^)
Now they want to automate the process with a solar tracker. They want someone to devise a solar tracker system to control the Helios 4
roaster. And better yet, they will award the winner with a grand prise of $1000 dollars. There is a $50 entry fee so they can know you are serions. (I would enter except my plate is to full right know, sounds fun.)
If you have questions I'm willing to assist you with your project. I would prefer initial contacts by phone:(651)426-4766
BTW, I am not affiliated with them in any way. I just like to see cool projects happen.
OK, get your buts in gear and make this happen for them.
Helios 4 and control room Helios 1 Sun Tracker Challenge
About Us:
My brother and I, Dave and Mike Hartkop, started our company five years ago. It grew out of a realization we had that we could roast organic coffee directly with solar energy, instead of using natural gas. Our first roaster, the Helios-1, used a satellite dish covered with mirrors and a roaster made from a broccoli strainer! It could roast about 1 pound of coffee in 15-20 min. of solar exposure.
In 2007, we moved from Oregon to southern Colorado in order to take advantage of the nearly year-round solar exposure in Pueblo Colorado. We opened our own retail coffee shop, called "Solar Roast Coffee", and have been in business ever since!
Our newest roaster, the Helios-4, employs a 35-foot wide solar concentrator, which we manually track to follow the sun via a pin-hole targeting camera and switches for up, down, left, and right. The new machine can roast up to 30 pounds of coffee in 15-20 minutes, and is also outfitted with an auxiliary propane burner to augment temperatures on extremely cold or cloudy days. (We DO purchase carbon credits in order to 'offset' the fuel we inadvertently burn.)
About the Contest:
Our contest, the 'Sun Tracker Challenge', directs teams to design and build a solar tracker system. The system must interface with the Helios-4 and will keep it aligned to the sun through an eight-hour roasting day. Entrants can use frame-grabs from our existing video-camera, install their own sensors, or install position encoders and use a timer-based method to accomplish the task! The winning team
receives $1000.00 cash an gets a write-up on our web site and local news. The top-ten finalists all receive Solar Roast Coffee prizes, including coffee and T-shirts.
June 10 Final Project Proposals Deadline -your team's project proposal is received. Proposal is just that: a proposal, not a finished project.
June 15 Top Ten Finalists announced -all proposals have been reviewed, ten most workable are chosen.
June 15-August 30 -Ten finalist teams build and test their sun-tracker projects, readying them for practical test in Pueblo.
September 1-30 -Practical Testing of top-ten Projects
October 10 Final Winners Announced -One first place, and prize choices for remaining 9 teams.
Details are online at:
http://solarroast.com/suntrackerchallenge.html
Interface Details:
Controlling the array movement:
Our control system includes a set of relays that can be driven directly by the team's project. Our control box has a female 5-Pin DIN connector (see image 5pinDIN.jpg) which is addressed as follows:
pin 1 Track toward verticalpin 2 Track toward horizonpin 3 Pan Clockwisepin 4 Pan Counterclockwisepin 5 Relays Common, floating.ring Ground
The internal relays driven are of type:
Siemens # VKP-35F42 relay. Sealed, PC mount power relay for high-current applications. 12 Vdc, 90 Ohm coil, 130 mA. SPDT contacts rated at 30 Amps. 1.02" x 0.84" x 0.86" high. The system is wired so that opposing directions can not be activated at the same time. See schematic (relaysschem01.jpg) The relay coils are electrically isolated from the control system, and are floating with respect to ground.
Powering your project:
A standard 2-socket 120VAC outlet is provided near the main control box. The outlet is GFCI protected and rated at 20A. Projects are expected to have their own internal fuses (15A or lower) in line with line power supplied. Your project box, to be connected to Solar Roaster Control box, should measure no larger than 18" x 18" x 12", (We need room for bags of green coffee!)
Sensors and cables:
100' cables to reach tower, or to reach horizontal track motor.
Use magnets to affix sensors to the system.
A rotary encoder, if used, should be fitted with ANSI #40 1/2" pitch sprocket, (bicycle chain). You provide encoder with sprocket attached, I will mount it!
Movement and Motors:
The outer Circular track is exactly 35' in diameter. The system is driven by two 90vdc gear motors with electronic speed controls. The speed-presets can be set by adjusting the electronic speed controller knobs internal with the system controls.
Default motor tracking and panning speeds are roughly 3 degrees per second. The movable array weighs 5300 pounds and is supported on 18 heavy iron casters. Kind of a "Lazy Susan" on steroids. There is minimal mechanical backlash at start and stop, and the system can be controlled manually with switches and targeting camera to an accuracy of +-1/8th degree, About 1/2 the suns image diameter.
An example 'manual controller' schematic of the interface.
Manual Controller and DIN connector
carter
* SunSeeker Project David Carter's PIC based solar tracker.Carter uses a method that acquires the sun by alternately panning in azimuth then elevation. The PIC reads output current and finds the maximum. This is done without light sensors just the charging current sensor.
The large servos, similar to radio controlled or RC servos, are driven with a pulse width signal.
The ON time defines the angle.The OFF time is not critical and should be from 10mS to 30mS.ON time of 1.0mS = 0 degrees
ON time of 1.5mS = 60 degreesON time of 2.0mS = 120 degrees
Interesting idea but not really the best way of tracking the sun. Light sensors work much better.
demartile
* "Rich DeMartile" <[email protected]>
* has a schematic of a solar tracker and mount based on a pair of CdS photo cells.
peterthinks
* "Peterthinks" <[email protected]> has made a solar tracker using RC servos. The system has a tracker based on BEAM technology. The beam circuits powered the RC servos. The tracker used only the power of the sun to move.
tag
* The Analog Guy Solar Trackers: ST2-48V5A SINGLE & DUAL AXIS SOLAR TRACKER 56V 5A MAXST2-12V DUAL AXIS SOLAR TRACKER 18V 0.5A MAXOne of my competiters.
jamesleyJamesley Dasse's Solar Tracker
Jamesley made this 2 axis PV solar tracker for a college project. His professor requires that he use a stepper motor drive. I designed a preliminary circuit for him to use. This circuit doesn't have rotation limits yet.
Electronics
Front View
Stepper DriveRear View
LED7 Solar Tracker Schematic
relaycds
Cadmium Sulfide Relay Tracker Schematic.
CdS1This is about the simplest tracker I know of. It uses a Radio Shack 275-249A relay. Adjust the sensitivity of the CdS cells with a Sharpie permanent marker as described bellow, in the Chace tracker. The picture tells it all.
This tracker is not as accurate as the electronic tracker but quite sufficient for use with PV panels.
limitops
How Limit Switches Operate
Limit switches are essential for servo motor operation with solar trackers. I made this diagram to help explain how they work.
Top. Normal operation between limit switches.Middle. The left limit switch has opened to stop movement to the left. To move to the right again the diode conducts current that allows movement to the right.Bottom. The right limit switch has opened to stop movement to the right. To move to the left again the diode conducts current that allows movement to the left.
Sellect a diode or rectifier rated at the maximum motor current plus some margine. Also the voltage should be at leat 100V and preferably 200V.
Needles to say, the limit switch must operate before the mechanical limits are reached. If the mechanical stop is reached before the switch the motor can draw quite high currents and can destroy the solar tracker.
led1
LED1 LED Sensor Relay Tracker Schematic.
LED1I have been looking for truly low cost and yet accurate conventional solar trackers. The CdS tracker is pretty good but lacks accuracy and sensitivity. I was thinking about using PV cells as the sensor. I was experimenting with LEDs and noticed they generate voltage in sunlight.
Bingo! This got me to thinking.
They generate quite a bit of voltage. The green ones generate about 1.65V, some as much a 1.74V. Not the piddley .55 volts of a silicon PV cell. How is this so? Well, it turns out green LEDs are made from Gallium Phosphide, a semiconductor with a much higher bandgap voltage.
I thought I had invented the use of LEDs as PV cells as I had never heard of this effect before. Well, after some investigating I found a number of references to this. The guys that had done the most work in this area were the people form the "BEAM" project. They make tiny solar powered robots and some used LED photo sensors.
I had been using a very low threshold MOSFET in a TO-92 package, BS107P. The threshold is about 1.5V. If I put two LEDs back to back, one fighting the other, the one with more light intensity wins. I thought I could use this to switch the MOSFET. And it worked.
By using one LED as a sort of power supply and the back to back pair connected from it to the MOSFET gate the circuit is complete. (This I have not seen elsewhere.) My implementation uses three power supply LEDs, aimed East, Up, and West. The sensor LEDs are aimed about 90 degrees from each other and at about 45 degrees either side of up. Of course the easterly pair will be a little to the east and the westerly pair a little to the west. This makes the center have a dead zone where tracking stops.
The circuit is quite sensitive. It brings the panel back to the east just after sun rise. The accuracy is quite good. You can calibrate the sensor by bending or aiming the LEDs a bit.
led2
LED2 LED Sensor Relay Tracker Schematic.
LED2Circuit 1 tends to chatter the relays under certain lighting conditions as there is no built in hysteresis. This version uses a Schmitt trigger hex inverter circuit to eliminate the chatter. It works better but is more complex.
Note! R4 and R5 are used to force parking when it gets dark. If parking is not desired don't use R4 and R5. Parking may not be desired in low power consumption applications.Also, the parking resistors, R4 and R5, reduce sensitivity a bit.
led5led5s5v
LED5S5V Simplified LED low power tracker.
LED5S5VI was looking for a much lower cost tracker for low power applications. One of these applications is a small lighting heliostat. This circuit uses small switching transistors. The maximum motor drive current is limited to about 250mA maximum at 5V.
I've tested the circuit on voltages from 3V to 21V. With some component changes it should be useful to 63V in a 36V PV panel system although I haven't tried this yet. With higher voltage and the use of heat sinks on the bridge transistors much higher currents should be possible.
The parts cost is very low. Parts cost estimated using Digikey prices. Ok, you can get stuff from the surplus stores but I will stick with Digikey.
1. 2N2222 NPN transistor 4 @ $0.21 = $0.842. 2N2907 PNP transistor 4 @ $0.21 = $0.843. 91 Ohm 1/2 W resistor 2 @ $0.06 = $0.124. 5 KOhm 1/4 W resistor 2 @ $0.06 = $0.125. 22 nF capacitor 1 @ $0.08 = $0.086. LED Green Lumex SSL-LX5093LGT 2 @ $0.12 = $0.24
Total = $2.24
$2.24, is this cheap enough?
led5s12v
LED5S12V Simplified LED low power tracker.
LED5S12V
This circuit uses small switching transistors. The maximum motor drive current is limited to about 100mA maximum at 12V.
1. 2N2222 NPN transistor 4 @ $0.21 = $0.842. 2N2907 PNP transistor 4 @ $0.21 = $0.843. 750 Ohm 1/2 W resistor 2 @ $0.06 = $0.124. 47 KOhm 1/4 W resistor 2 @ $0.06 = $0.125. 100 KOhm 1/4 W resistor 2 @ $0.06 = $0.126. 22 nF capacitor 1 @ $0.08 = $0.087. LED Green Lumex SSL-LX5093LGT 2 @ $0.12 = $0.24 Total = $2.36
led5connections
LED5 Connections
led5forsale
I have the LED5 series trackers for sale.Yes, I know, not everyone wants to build these from scratch so I made a PC board for the LED5 series.
The single axis board is a bit less than 1/2" x 1" and the dual axis is a bit less than 1" x 1".
paypalled5s5v
LED5S5V 5 Volt Single Axis Low Power Tracker including shipping using PayPal.$26us total.
paypalled5d5v
LED5D5V 5 Volt Dual Axis Low Power Tracker including shipping using PayPal.$48us total.
paypalled5s12v
LED5S12V 12 Volt Single Axis Low Power Tracker including shipping using PayPal.$26us total.
paypalled5d12v
LED5D12V 12 Volt Dual Axis Low Power Tracker including shipping using PayPal.$48us total.
led5plc
LED5S12V Modified for use with a PLC.
LED5S24VPLCDNThe schematic is for the "Pull Down" variant.
This version of the basic LED5 can be used as a sensor input to a PLC, Programmable Logic Controller. The output is an "Open Collector" NPN transistor and assumes the PLC has the associated "Pull Up" resistors.
The actual voltage range is from 4V to 28V. (I can make higher voltage variants also.)
I can also make 24V LED5 trackers with totem pole outputs which have both pull up and pull down transistors. Essentially the same as the standard trackers but with limited drive capabilities.
This circuit does not have a parking function. Parking and Reverse Inhibit functions are best performed in the software of the PLC using timming functions.
Note! If you want a 5.1k 1/8W passive load resister can be added if requested.
paypalled5s24vplcdn
LED5S24VPLCDN Single Axis Sensor for PLCs with PULL DOWN Transistors including shipping using PayPal.$26us total.
paypalled5s24vplcdn5k
LED5S24VPLCDN Single Axis Sensor for PLCs with PULL DOWN Transistors & 5k passive pullup resistors including shipping using PayPal.$26us total.
paypalled5d24vplcdn
LED5S24VPLCDN Dual Axis Sensor for PLCs with PULL DOWN Transistors including shipping using PayPal.$48us total.
Some applications need "Pull Up" transistor outputs. This is done by using PNP transistors in the output.
paypalled5s24vplcup
LED5S24VPLCUP Single Axis Sensor for PLCs with PULL UP Transistors including shipping using PayPal.$26us total.
paypalled5d24vplcup
LED5S24VPLCUP Dual Axis Sensor for PLCs with PULL UP Transistors including shipping using PayPal.$48us total.
2l003
Grainger 2L003 Gear Motor This is a 12VDC gear motor from Grainger's.This controller works well with the 2L003.
This motor is an off the shelf motor from Grainger's. Stock number 2L003. It's rated for .45 RPM at 50 In Lbs. The motor current is less than 100mA at 12V and about 50mA at 5V.
tamiya
Tamiya has a number of Model Gear boxes.The motors supplied are rated for about 3V. They draw a bit to much current for the 2N2222-2N2907 driver transistors.
lamble
LED5Stewart Lamble built this version.He subistuted BD135 (NPN) and BD136 (PNP) transistors.
ledfast
LEDFAST Acting Analog Solar Tracker.
LEDFASTI needed a special solar tracker that is very fast acting. The action needed to move a PV panel from lock to lock in a few seconds. It was important that little overshoot occur. This circuit satisfies these requirements.
1. R7/R8 form a voltage divider to produce a voltage of 1/2 of VCC and applied to the non inverting inputs of the OpAmps.
2. The OpAmps are setup to have a gain of 1000X through R3/R1 and R4/R2. Capacitor C1/C2 limit the high frequency response of the circuit to prevent oscillations.
3. The LED sensor circuits need to be high impedance so are isolated from the gain resistors through resistors R5 and R6.
4. I use large 10mm "Green" LEDs with clear cases. They are made by Lumex, but all normal LEDs can work. (Don't use the White LEDs as they are not normal types.) The LEDs act as small photo voltaic generators. Since LED1 & LED2 sensors are connected back to back the sensor that has the greater light intensity expresses its voltage over that of the sensor with lessor light intensity. Imbalance in the light on the sensors produces a differential voltage which is amplified and presented to the motor. As the light approaches balance the motor differential voltage approaches zero resulting in no motor current.
5. The LM324 has an output current drive capability of >10mA. Transistor pairs Q1/Q2 & Q3/Q4 form unity voltage gain emitter follower current gain amplifiers. With power transistors that have a gain of 100 the motor drive current can be about 1A or more.
6. VCC can be from about 6V to an absolute maximum of 32V. Other OpAmps can be used for a greater VCC range.
7. Note! Limit switches are required in the motor circuits. See:How Limit Switches Operate.
8. There has to be a down side though. This is a true analog circuit that drives the output transistors in a linear manor therefore power is wasted when slowing the motors. Heat sinks may be required.
9. This circuit is not generally suitable for use with normal high efficiency solar tracking applications. It is best suitable for school projects.
led3
LED3 LED Sensor Electronic Tracker with H-Bridge Drive.
LED3I decided to make a commercial surface mount PC board using the LED2 sensor concept. It is quite sensitive and can track to a few
degrees of accuracy in bright sunlight. If a blocking shadow is used the accuracy is better then 1/4 degree, that's about as good as you can get with an active feedback sensor. The board is a tiny .7"x1.4".
Note! I have replaced the LED3 with the much more capable LED3X series of solar trackers. See below.
This circuit uses power MOSFET drivers and is designed to operate satellite dish linear actuators, however most any DC motor can be used. The power drivers are capable of delivering about 10 amps of peak current, maybe more. When better transistors become available this current can be increased. The drivers operate the actuators in pulses of about .3 second every 3 seconds or a 10% duty cycle. This eliminates the needed for a heat sink on the transistors. Neat huh!
I haven't decided if 10% is the best duty cycle to use. Less will make the tracking slower but, we don't need speed anyway. I will determine this when I get better weather. Slow tracking speed helps in partly cloudy condition. This prevents the tracker from making unnecessary movements when clouds move by.
No electrical adjustments are required. The LEDs can be mechanically adjusted for optimum tracking performance by aiming them after the circuit board is mounted.
led3shadow
To improve accuracy, ie. with concentrators such as troughs or dishes, a blocking shadow can be placed in front. The shadow just covers the two inner LEDs when aimed at the sun. Similar to the shadow on the Chace Tracker.
I have used a band of metal about .5" in width at about 6" from the LED3. If the LED3 is used for E-W tracking the band is oriented N-S. Conversely, if the LED3 is used for N-S tracking the band is oriented E-W. The shadow device is not particularly critical. For instance, I have used black electrical tape on the weather dome and it worked well.
led3specifications
Power Supply Voltage 8 Volts to 22 Volts inclusive.
The 8V minimum is specified to prevent damage to the MOSFET power drivers. The damage is due to operating them in the linear region with a load. This causes excessive power to be dissipated in the MOSFET with a resultant damaging temperature rise.
The 22 volt maximum is defined by the voltage tolerance of 24V protection zener. This zener protects the power MOSFETs from seeing damaging breakdown voltages. During testing I had several failures when operating from a car battery while the alternator was running. It was determined that the alternator was producing voltage spikes in excess of the 30V breakdown specification of the MOSFETs.
The 24V zener has an initial tolerance of 5%. So the maximum continuous voltage that can be applied before conduction can occur is 22.8V or so.Most PV panels don't output more than 22V in open circuit. You should check for sure. If they do go to high in voltage a simple power regulator should be added to limit the maximum voltage.
Load Current Continuous 5 Amp resistive.
The power MOSFETs are rated at over 10A at 25°F. A conservative derating of 50% is prudent especially in hot weather conditions.
Load Current Intermitant 10 Amp intermitant at 10mS width once per timing cycle.
The Power MOSFETs have an absolute maximum current rating of 30A, but this is with ideal conditions where the temperature is 25°F and very fast gate rise times. The LED3 has a relatively slow gate rise time and may be operated at quite high temperatures sue to the weather. I think 10A at about 10mS is adequate for normal tracking applications.If higher current motors are required a power amplifier may be needed. See:http://www.redrok.com/electron.htm#power
I should note that the satellite dish actuator I use normally consumes about 290mA of current at 13.8VDC. This actuator is capable of driving a 15' dish with 1500lb of force. You don't need a high powered drive, just a slow forceful one.Think slow!
Operating Temperature -40°F to 185°F or -40°C to 85°C
The circuit board and sensor assembly of the Chace tracker.
The circuit is not water proof so a protective plastic dome is needed. I have used 2 liter clear plastic soda bottles. They last a long time, at least 5 years for one I have used, probably a lot more. This circuit will fit into the 20 Oz. size. The plastic bottle chosen needs to have a round bottom, the type that comes with the black plastic bottom which is removed. The type with the molded in feet don't work very well as they diffract the light too much.
Glass jars are even worse optically if looking through the bottom.
Any one out there with a good idea for a better weather dome?
In Minnesota I have snow that builds up on the top of the dome. This snow is quite reflective and can confuse the sensors as to the correct direction for the brightest portion of the sky when in the sky is overcast. It's easy to just brush the snow of but this is not always timely. I have experimented with putting black opaque paper inside the dome to eliminate the light from the snow. Another paper light blocker can be put under the sensors to stop the reflected light from the snow on the ground.
dome
Dome on Chace tackerThis weather dome is made from a 2 liter pop bottle.
jiffI have tried and like using plastic Jiff Peanut jars
Jiff peanut butter jar.
Jiff peanut butter jar with only the lid.
dcbDCB's implementation of the LED3 tracker with Pyrex Weather Dome.This dome is made from an unusual deep style Petri dish.
East View
West View
Assembled
Top View Without Dome
View From BelowLong View
The Base
doc
Doc's implementation of the LED3 tracker with a Fruit Jar Weather Dome.Doc emailed this to me:
The power produced from the system is run to the main house. In the house, the 120 volt service is connected to its own fuse box to run all of my 120 volt stuff. The LED3 increased the output of the 4 panel array by 50%, as compared to the output of an identical 4 panel array mounted on the roof.
During mid-day, the power output of my system bulk charges the batteries and the C40 disconnects the solar panels to keep from over-charging the batteries. This never occurred before I installed the LED3. This is great!!
LED3 in Fruit Jar PV Panel
PV Panel
Panel with LED3 Back of Mount
Power Controller
Battery Pack
danbennet
Dan Bennet's Dish.12 foot parabolic dish with 10,300 1" pieces of mirrors on it. It weighs around 1,200 lbs with the boiler .
LED3 in Fruit Jar
wolfendale
Martin Wolfendale's implementation of the LED3 tracker with a machined plastic Weather Dome.Martins PV panel mount is homemade and looks very nice. He is in Austrailia so things might seem a bit reversed to us northerners.
Overall View
Closer Mount and Connections
Wearher Dome in Upper Corner Closeup of Weather Dome
LED3
gary
Gary <[email protected]> has suggested making the dome from Lexan. He wrote:It's fairly easy to make a perfect dome out of Lexan.Make a 2 piece mould out of whatever you can find that's the right size.Heat up a piece of Lexan in your oven at about 200F for about 5 min.Put it on the mould and press and release.Trim off the excess after it cools.If you want really good optics leave room in the mould for a piece of flannel on each side.Scratches are polished out with toothpaste.I Got this from EAA Sport Aviation to make nice wing tip strobe light covers.
mrea2001Demo of my tracker at the 2001 Midwest Renewable Energy Fair
Look at all the people
Having fun igniting sticks of wood at the prime focus of the dish. That flash of white is smoke after about ½ a second. It also melts holes in aluminum cans in about a second.
A small Stirling engine mounted where the electronics used to be on the small PrimeStar dish. Reflective Mylar was glued to the surface.
The north view
View from the SE. This mount is similar to that of a Poulek Traxle. This mount is very sturdy compared to the conventional Daisy mount.
mrea2002Demo of my trackers at the 2002 Midwest Renewable Energy Fair
Solar trackers
led5dlighting
Lighting "Receiver Axis" heliostat with dual axis LED5D5V solar tracker.
led5spv
Small PV Panel with LED5S5V solar tracker. This one is powered from the PV panel it controls.
Two "Receiver Axis" heliostats
Back of large "Receiver Axis" heliostat.
bisectordrive
Bisector Drive on large "Receiver Axis" heliostat.
led5ddome
Dual axis LED5D5V solar tracker on large "Receiver Axis" heliostat.
mrea2003Demo of my trackers at the 2003 Midwest Renewable Energy Fair
mrea2003trackers mrea2003ledtv1&dome mrea2003ledtv1b mrea2003ledtv1c
A bevy of 4 solar trackers and mounts.
Prototype LEDTV1 solar tracker. The weather dome is a Lexan canister I got at Wall-Mart. The tracker is based on a MicroChip PIC12F675 8 pin microprocessor.
Prototype LEDTV1 solar tracker. In this case it drives an Alliance U-100 Tenna Rotor TV antenna rotator. This setup charged 2 junk car batteries to operate both this and the dish trackers.
Prototype LEDTV1 solar tracker. In this case it drives a Cornell Dubillar ham radio antenna rotator. It was great fun cooking mini killbasas on the Primestar dish.
mrea2003smallpv
Small PV Panel with LED5S12V solar tracker. This one is powered from the small PV panel it tracks and supplies power to it and the LED5D12V heliostat tracker.
mrea2003heliostat
Lighting "Receiver Axis" heliostat with dual axis LED5D12V solar tracker. This heliostat continuously illuminated my Red Rock sign.
The Red Rock Energy sign. I apologise for not taking the picture earlier because my tent was blocking the light.
Layoutledshex3molex
Molex ConnectorThe tracker consists of pairs of LED photo sensors. Each pair controls the voltage applied to one terminal of the actuator motor.
led3operation
When the easterly pair says go west the minus terminal is grounded. When the westerly pair says go west the positive terminal is connected to plus and we get westerly movement. Or vise versa for easterly movement
When they disagree then either both motor terminals are grounded or have plus on them, and we get no movement. There are four operational states for the sensors to be in.Each LED pair tends to move the tracker East or West.An LED pair tends to move to the West orAn LED pair tends to move to the East.Each of the LED pairs controls one side of the H-bridge.
LED Pair 1-3 LED Pair 2-4 H-bridge Left H-bridge Right Movement
West West Low High Move West
West East Low Low Stopped
East West High High Stopped
East East High Low Move East
Note! Unlike most H-Bridge drivers where both sides are always driving the load this circuit has independent drives for each side. This allows the motor to stop when both sides are high or low. The motor moves when they are different.
In addition, both sides have the top MOSFETs turned off most of the time until the clock enables movement by periodically pulling R9 and R11 low.
Q3 and Q4 form a gated level shifter. To see how this driver works think of the bottom end of R9 and R11 being grounded when the top transistor is to be enabled.
Also the driver for the left side are inverted from the driver on the right side. This is a method for returning the tracker to the east, for parking, if R2 and R3 are used. This way Q1A will be enabled and Q2B will be on when in the dark.
parking
In cloudy or overcast weather the tracker seeks the brightest part of the sky. At night it moves to the easterly parking position. The parking position puts the panel at a steep angle so night time snow doesn't accumulate as much in the winter. A westerly parking position is obtained by mounting the tracker upside down and reversing the leads to the actuator motor.
led3x
LED3X LED Sensor Electronic Tracker with H-Bridge Drive.
LED3X Solar TrackerThe LED3 using surface technics was just to hard to assemble in a timly manor as sales were increasing. I needed a circuit that could be built with mostly through hole components. At the same time, there were other features and enhansments that I thought were needed. This was the impetus for the LED3X series of solar trackers.
This circuit uses power MOSFET drivers and is designed to operate satellite dish linear actuators, however most any DC motor can be used. The power drivers are capable of delivering about 50 amps of peak current, maybe more. When better transistors become available this current can be increased. The large power MOSFETS, 72A, when operated at low duty cycle or low currents eliminates the needed for a heat sink on the transistors. Neat huh!
The duty cycle is adjustable from 0% to nearly 100%. Idealy tracking from stop to stop should be 10 to 30 minutes. The duty cycle helps to slow down the motor drive speed. Less duty cycle will make the tracking slower but, we don't need speed anyway. Slow tracking speed helps in partly cloudy condition. This prevents the tracker from making unnecessary movements when clouds move by.
led3xshadow
To improve accuracy, ie. with concentrators such as troughs or dishes, a shadow blocker can be placed in front. Similar to the shadow blocker on the Chace Tracker or like this:
OK, this is an example of a dual axis versio.The single axis version uses a strip of meta.Cool weather dome!! As I recall the dome is polycarbonate and from the oil or water traps on air lines and regulator s
I have used a band of metal about .5" in width at about 2" from the LED3X sensor. If the LED3X is used for E-W tracking the band is oriented N-S. Conversely, if the LED3X is used for N-S tracking the band is oriented E-W. The shadow device is not particularly critical. For instance, I have used black electrical tape on the weather dome and it worked well.
led3xremotesensor
LED3X Remote Sensor
The remote sensor comes can be configured in several flavors.1. Single axis2. Dual axisAnd parking or no-parking on either axes.
The PC board is configured in 2 halves. Each half is an individual single axis sensor. For single axis use the board is cut in half or dual axis if left whole. Depending on which components, positions, and jumpers installed all the configurations can be obtained.
led3xremotesensorschematic
Dual Remote Sensor Schematic
led3xs24vspecifications
LED3X Specifications
For a more detailed set of specifications, options, and pictures see the web page devoted to assembling the kit. And a lot more pictures and application information.
Power Supply Voltage 10.5 Volts to 44 Volts inclusive.
The 10.5V minimum is specified as the under voltage point. Less voltage protects the power mosfet in the H-bridge driver circuitry.
The 44 volt maximum is defined by the voltage tolerance of the 51V protection zener. This zener protects the power MOSFETs from seeing damaging breakdown voltages.The 51V zener has an initial tolerance of 5%. So the maximum continuous voltage that can be applied before conduction can occur is 48V or so.Most PV panels don't output more than 44V in open circuit. You should check for sure. If they do go too high in voltage a simple power regulator should be added to limit the maximum voltage.
Load Current Continuous 9 Amp resistive.
The power MOSFETs are rated at over 70A at 25°F. A conservative derating of 50% is prudent especially in hot weather conditions.
Load Current Intermitant 20 Amp intermitant at 1S width once per timing cycle of 60S.
The Power MOSFETs have an absolute maximum current rating of 72A, but this is with ideal conditions where the temperature is 25°F and very fast gate rise times. The LED3x has a relatively slow gate rise time and may be operated at quite high temperatures due to the weather. I think 20A at about 1S is adequate for normal tracking applications.If higher current motors are required a power amplifier may be needed. See:http://www.redrok.com/electron.htm#power
I should note that the satellite dish actuator I use normally consumes about 290mA of current at 13.8VDC. This actuator is capable of driving a 15' dish with 1500lb of force. You don't need a high powered drive, just a slow forceful one.Think slow!
Operating Temperature -40°F to 185°F or -40°C to 85°C
led3xforsale
LED3XS24Vc3 For Sale
Please go to this page:http://www.redrok.com/led3xassm.htm#led3xforsale
power
Some have expressed an interest in driving high powered loads beyond the capabilities of the H-Bridge driver transistors. To this end I developed several high powered driver circuits, (actually their almost the same circuit as in the relay trackers).
relaydc1
RelayDC1Relay circuit that uses DC relays with 12VDC coils. The DC motor in this case is a permanent magnet type that is reversible.
relayac1
RelayAC1Relay circuit that uses AC relays with 12VDC coils. The AC motor in this case is a capacitor run type.
relayac2
RelayAC2Relay circuit that uses AC Solid State relays with 3 to 32 VDC control inputs. The AC motor in this case is a capacitor run type.
manualled3manual
LED3XManual
Some have expressed an interest in adding a switch to manually move the array for test purposes. One of these circuits, when added between the tracker and actuator, will allow manual movement. T
Since I do the assembling variations can be easily made for such things as a change in the timing of the oscillator for other duty cycles or to disable the parking feature. I am currently selling the assembled units without the parking feature.
assemblyled3x
Assembly & Opperating Instructions for the LED3X series. Plus a lot of pictures and examples.
led3xenergy
The circuit draws about 15mA when idling. It can operate at temperatures to -40F or up to 158F. Its designed to operate from a 12V or 24V lead acid power source. I generally recommend using a 36V actuator on 12V.
The daily energy consumed is quite small. My actuator draws about 290mA and can go from stop to stop and back in about 5 minutes. So:((.015A * 24hr/day) + (.290A * 5min/day / 60min/hr)) * 13.8V = 5.3Whr/dayOr about 5Whr/day, which is pretty small.
A very small 5W or even a 2W PV panel and small gel cell lead acid battery is a good combination for the power source to run the system.
I intend that this circuit will supplant the Chace tracker as its simpler to build and adjust.
For two axis tracking two circuits are needed. However, for PV panels the second axis only adds about 5% on the average and may not warrant the added expense.
economics
Many have said that it makes no sense to use a solar tracker with PV systems as it is cheaper to just add an extra panel for every three. To this I say bunk.
Using the NREL data:My link.http://rredc.nrel.gov/solar/pubs/redbook/redbook_index.html
I find that in Minnesota a single axis tracking PV panel will have a 40% increase in output in December and a 100% increase in June.In Minnesota:A PV panel with 15% efficiencyin December tilted to your latitude plus 15 degrees.http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/atlas/2 to 3 kWh/m^2/day lets say 2.5 solar2.5 kWh/m^2/day * 15% = .375kWh/m^2/day electric
Or a single axis north-south tracking panel at lat. +15 deg.3 to 4 kWh/m^2/day lets say 3.5 solar3.5 kWh/m^2/day * 15% = .525kWh/m^2/day electric.525 / .375 = 140%This shows 40% improvement with a tracker in December.
Lets do it in June:4 to 5 kWh/m^2/day lets say 4.5 solar4.5 kWh/m^2/day * 15% = .675kWh/m^2/day electric
Or a single axis north-south tracking panel at lat. -15 deg.8 to 10 kWh/m^2/day lets say 9 solar9 kWh/m^2/day * 15% = 1.35kWh/m^2/day electricThat's a 100% improvement with a tracker in June.
Of course your location will have different results. For instance I just did it for San Jose, CA and got an increase of only 14% in both June and December. Clearly this is not the best place to do solar tracking.
Here are the 4 maps that I used.nrelmaps
Click the map!
The full set of maps from NREL are here.
I don't have a cost for the tracking mount but the actuator I'm using costs about $140us and my tracker is $35us. PV panels now are about $5us/W so a 100 watt panel costs $500us. Using a system of 3 panels this is $1500us.
Since the tracker delivers at least 40% more output, in December, it would be fair to say that the tracker has an equivalent value of $600us in a 3 panel 300W system. I can't see the tracking mount would cost $600-$140-$35=$425 more than the equivalent stationary mount that has to hold at least 4 PV panels. Of course, the comparison is even better in June with the 100% increase.
Today there are many obsolete C-band satellite dishes. These have polar axis mounts which are almost ideal for use with arrays of PV panels. Remove the dish and install racks to support the panels. They are well designed and very strong. They have all the needed hardware including the motor actuator. Besides they are often free for the asking.
I am convinced that the best and strongest mount for PVs at ground level is one based on the design example of:
* Traxle
Poulek Solarby Martin PoulekGary A. Werner, President GWM CorporationPolar mount with tracker.The tripod support arrangement is very strong with light weight construction.
aps
* APS Solar's "Tilt Tracker". Similar to Poulek Solar's Traxle, with a clockwork tracker. The second axis, the tilt axis, is adjustable for a few percent improvement in total output. The actuators are hydraulic.
powerlight
* PowerLight A bigger version, similar to Poulek Solar's Traxle
sunpower
* Sun PowerLight
szymanski
* Martin Szymanski's variation of a Tripod Tracking Mount
tripod
TriPod Mount
This is my version of Poulek's mount. I call it the TriPod Mount. This mount is cheap and crude but easy to make, especially for demonstrations. It's easy to build and knock down. Its quite portable.A proposed Stationary Receiver Dish on a Tripod Mount.A proposed Stationary Fresnel Lens on a Tripod Mount.
It's made from PV plastic sewer pipe.1. The legs are fitted with end caps.2. The foot caps are drilled and have long bolts protruding through to be pushed into the ground.3. The support legs have "I" bolts fitted to the top caps.4. The main polar axis leg has a large bolt that is fitted through the "I" bolts of the support legs.(The Primestar mount doesn't allow the pipe to go all the way through so I made a compromise and have this large top bolt mounted to the dish support. Although the Primestar mount has a method to manually adjust for declination.)5. The polar leg needs to rotate. To do this side pipes are glued on to the polar and one of the support legs.6. The satellite dish linear actuator is fitted to the side pipes.7. To set it up just adjust the support legs until the polar tube is aimed at the pole star. This is due north and angled at exactly your latitude.8. To make sure the thing doesn't blow away I have a heavy nylon cord, ( not in the pictures ), tied from the top of the polar leg
down to the earth. I used a screw into the ground dog leash stake.9. Don't bolt the dish and PV panel to tightly. This will allow some manual adjusting.
There are some compromises to this example.1. The actuator can only rotate the polar leg about 150°. A better way would be to have a pulley and cable to get the rotation to 270° or so. 2. The Primestar mount is not ideal. A better mount would allow the polar leg to protrude fully.3. A longer polar leg would allow more rotation without interfering with the supporting legs.
Improvements1. For larger equipment one should make the tripod from steel cold water pipe. This would make things much sturdier.2. Make the polar rotating device using a large pulley and cable to allow more rotation.
led4
LED4 LED Sensor Electronic Tracker with Simple Solar Charge Controller.
LED4The "LED3" light sensor works very well. It is sensitive, accurate, and cheap. A couple of years ago I had devised a simple solar charge controller I called "Shunt 2". I thought it would be a good idea to combine them into a single PC board called the LED4.
Note! I no longer sell the LED4 as it was replaced by the much more capable LED3X. Ok, the LED3X doesn't have a charge controller but this isn't really required to run the tracker.
The design philosophy for this tracker was to make it more robust and self contained. I included a charge controller for rechargeable batteries intending them to be NiCds to run the actuators. Since the charger is there it might as well be capable of running a large PV panel with lead acid batteries.
Note! this charger is not intended to charge the expensive system batteries. Leave that job to the high end smart charger such as those by Trace, Outback, and others.
It can also run a very small PV panel to charge the local NiCds or NiMH batteries. These batteries work well over a wide temperature range.
I will test the ability of the sensors to be at the end of a long cable. I will test this using 1000' of 4 wire telephone cable. 8 wire Cat5 cable should also work with the extra wires driving the actuators.
With the use of long Cat5 cable the main board can be inside a heated battery room. Of course you still have to run the heavy gauge main charging wire pair to the battery room. The advantage of having the batteries in a heated room is temperature compensation won't be needed.
ledshex4
LED4 Schematic
LED4 Layoutled4connections ledsensor01
LED4 Pinout Alternate LED4 Sensor Schematic
led4featuresLED4 Features
Separate LED Light Sensors
The signal sent back from the sensor can be sent a considerable distance since the current flow is minimal. However, static electric discharge could be a problem if the sensor is more than about 6 feet or so from the main board. If long distances are needed please Email me for advice.
Under voltage Shutdown Protection
Shuts down the actuator motor drive when the battery voltage drops below about 10½ volts.
Built In Charge Controller
Designed for use with nominal 13.8 volt battery systems. The charger is designed for controlling 13.8 volt 125 watt PV panels. There is no provision for either temperature compensation or multiple charging strategies.
Larger Power Transistors
The power MOSFET transistors are much more robust than in the LED3. It uses IRF5305 and IRLZ44N transistors from International Rectifier. The IRF5305 P-channel MOSFET has an on resistance of about 60mOhm and the IRLZ44N N-channel MOSFET has an on resistance of about 20mOhm.
No need for a heat sink
A 125 watt PV panel can deliver about 9 amps of current. The maximum wattage dissipated by the IRLZ44N shunt transistor under these conditions is about 1.6 watts continuously. The Schottky Barrier series protection diode is rated for about 9 amps.The H-bridge transistors are pulsed at about a 10% duty cycle. I'm rating the actuator maximum pulsed current at about 16 amps. If you want to continuously drive the actuator keep it below 5 amps.The IRF5305 has a maximum current rating of 110 amps and the IRLZ44N has a maximum current rating of 160 amps so if the currents are kept to below my system rating no heat sinks will be needed.
Built with Through Through hole construction allows the average home brew guy the ability to easily put the LED4 tracker together either as
Hole Componentsa kit or scratch built.I can supply the PC boards separatly for $9.00us.
Operating Temperature Range
-40°F to 185°F or -40°C to 85°C
vdish1
Virgil Vinz's faceted dish with LED4 tracker in a Peanut Butter Jar Weather Dome.
This dish is to be used to run a small steam engine. The mirrors are 6" Lucite squares. The ribs are cut from parabolic sections.
The receiver is a flash tube type. The spiral copper tubing is cast into an aluminum block. The Pyrex cooking dish is the transparent insulating cover. The backside is insulated with fiberglass. The indicated temperature is about 1100°F. The concentration ratio is about 20X or so given the receiver is larger than the mirror tiles.
vdish1overall
Faceted Dish
vdish1mount
Steam Generator Mount
vdish1steamgenerator
Steam Generator
vdish1melting
Melting aluminum canswith a propane powered"weed burner" blow torch.The angle iron and steelplate mold is heated andthe cans poured in.
vdish1flashtube
Spiral copper flash tubesimbeded in the aluminum.The tubing is 3/8th inchtubing and about 4' inlength. Be careful not toover heat the aluminum asit is possible to melt thecopper. Filling the tubingwith sand helps to preventmelting by absorbing someheat when cooling.
vdish1receiver
Front side of receiverpainted flat black.
vdish1ribs
Parabolic Ribs and PolarTripod Mount
vdish1drive
Belt Drive
vdish1led4
LED4 in plastic PeanutButter Jar
concentratortemperature
Calculations of Concentrator Temperature Rise.A number of people have asked the question:"How hot will my concentrator get?"or:"How much concentration will I need to get to a certain temperature?"
Let's use this example:"A twelve foot dish focused to a 6 in., 3 in., or one 1 in., diameter receiver.How can you estimate the temperature of the various smaller diameters?"
Lets review:X factor is the ratio of the captured sunlight area divided by the radiating surface area of the receiver. Assuming the back side is well insulated.
12' foot C-band satellite dishes have a focal length of about 10'. At least mine does.
The sun has an image diameter of about 1/2 degree of arc. At 10' this perfectly focused diameter would be:
( 2 * tan( .5deg / 2 ) * 10' = .087' * 12"/1' = 1.04"
That's for a perfect parabola. C-band dishes aren't nearly that accurate. So maybe the diameter is about 3".
So firstly, you can't get to a 1" diameter.
3" is about (144"/3")^2 = 2304X6" is about (144"/6")^2 = 576X
"How can you estimate the temperature of the various smaller diameters?"
The simple answer is you can't. Temperature of a receiver is only loosely related to X. The more important factors are:
1. Rate of heat removal. For instance if the heat removal is infinite then the temperature would be the same as ambient.2. The selectivity of the surface of the receiver. Good selective surfaces such as black nickel oxide are pretty good and will attain a higher temperature due to not radiating as much heat back to space.3. A limiting factor is the surface temperature of the sun. Generally considered to be about 10000F or about 5600C.4. The quality of the reflectivity of the mirror. I usually assume this at 80% to 85% regardless of what the manufacturer of the Mylar films say.
Another way to help in the understanding of receiver temperature is it is a kind of balance. The receiver, insulated on the back side, radiates into a hemisphere. The dish appears to cover a portion of the hemisphere.The ratio:
(dish angular surface area) / (a hemisphere) * 10000F = Temp
This implies that a receiver temperature is independent of X.
And this is true. However larger receivers have other losses such as:
1. Convection loss2. Process heat removal
What are you trying to do?Generate steam?Steam receivers don't have to be particularly small as the temperatures are limited by the steam system.See our experimental receiver above.
This dish has a no thermal output temperature rise of about 1100F with a concentration of about 20X. We estimate this is about correct for the dish angular area.
sphericalcollectormath
* Here is an Excel spreadsheet to do the math. http://www.redrok.com/sphericalcollectormath.xls
Another way to use this information on our system.
1100F = 0% efficiency. ( No output of steam.) 50F = 100% efficiency ( Perfect cooling of the receiver.)
Other efficiencies are approximately linear between these. 837F = 25% 575F = 50% 312F = 75%
Actually the lower temperatures will have higher efficiencies because convection losses are reduced.Does this make sense?
martins
<Martin Szymanski's> variation of a Tripod Tracking Mount
* Welcomb to Copperopolis Martin's web page.
View from the south. Martin lives in southern California about 100 miles from the ocean. This is why the array has a severe tilt back.
Weather dome using a glass lamp fixture obtained at Home Depot.That's an LED3 inside there.
LED4 under test.Note! The LED sensors are directly mounted on the main board and the remote sensor board wasn't used.
Pre Construction
Base hole ready for concrete.
assemblyled4
Assembly Instructions for the LED4.opperatingled4
Operating Instructions for the LED4.
Actuator.I have more circuits here along with a bunch of data about Satellite dish linear actuators. The circuits on this page are not finished nor fully tested.
chace1
Jeremiah Chace's Analog Solar Tracker Schematic.
Chace1
Tracker Schematic.
Some guys on the net have expressed a desire for a simple analog solar tracker to operate their concentrator projects. Jeremiah Chace sent me a schematic for such a tracker. His circuit was based on a Cadmium Sulfide, CdS, photo cell with a relay output. There were a couple of problems with the circuit. After some discussions with him I made some improvements and here are the results.
The basic operation is essentially that of 2 separate photo sensor circuits in pairs. Each separate sensor circuit has a control pot to set it's sensitivity for bright sunlight.
It is important to have a thorough understanding of the operation of the circuit in order to be successful in making the correct adjustments for acceptable operation. One must do the adjustments on a clear cloudless day. At the very least wait until the sun is between clouds.
CdS cells have a wide variance in the resistance they exhibit in bright sunlight. Generally the resistance is too low for this type of circuit. I have found that the CdS cells can be modified to have higher resistance by painting the cells with a black marker. I use a Sharpie black permanent marker. I paint this on all sides and edges. If you get too much on it can be removed with fingernail polish remover or acetone.
The correct amount of blackening is when the adjustment pot is approximately at mid setting when the circuit is tilted so about half of the cell is illuminated by sunlight and half covered by the light blocker. Repeat this painting of the cells until all 4 CdS cells are adjusted.
I have found a helpful tool to make the adjustment easier. Just use a small mirror to reflect sunlight onto the CdS cell. By covering one cell with the finger and reflecting light onto the other cell the tracker can be moved at will. This allows the cell sensitivity adjustments to be easily made.
The painting procedure would not be very easy to get accurate were it not for the pot. The settings seem stable but I haven't had very much time on the circuit. I suspect that the most problem would be the fading of the black marker. If this happens I suppose a different more permanent light filter coating could be devised. Possibly Parsons Black which is carbon lampblack in spar varnish.
P.S. I have had about 4 months of operation on the tracker and have not seen any problems.
There have been days where no bright solar radiation falls on the sensors the tracker just stays in the last position that movement occurred. The panel is not at the optimum orientation to gather the maximum amount of energy from this diffuse radiation during these times.
In the long run this is not a problem. Of course the amount of energy is less than optimum during cloudy times. The gain due to tracking greatly exceeds the dim time loss.
chaceshadow
Sensor and shadow light blocker.
Each CdS cell of a pair is on each side of a central light divider with a top light blocker. The light blocker is just wide enough to block both CdS cells when the sun is dead on center. In this example the light divider is made of rubber and the light blocker is an old aluminized 5.25" floppy disk write protector. The materials used are not critical. They need only be light opaque. The light divider should be black and non reflective. The blocker could be made from reflective aluminum foil to prevent heat buildup.
Note! The CdS cells are highly angled in such a way that they are generally aimed at a portion of the sky that is away from the sun. This helps to get the platform moving in the right direction when far off track.
If either CdS cell is uncovered by the light blocker it will conduct heavily and the associated power driver will move the actuator in such a way that the CdS cell is again covered.
When neither CdS cell is exposed to bright light the actuator is prevented from moving. This leaves the tracker at the last moved to position. Little power is expended searching for a new position when in dim light.
The light blocker is supposed to never let both CdS cell be exposed to bright light. However it could happen. If this condition occurs the actuator is prevented from moving or hunting. This saves power by moving only when necessary.
This schematic is for one axis. The second axis is the same as the first and uses the other half of the LM339 comparator.
When the sun is behind clouds the actuator is prevented from moving or hunting. When the sun comes back out the tracker will move toward it again.
When the sun sets the platform remains aimed to the west. In the morning the easterly aimed CdS cell becomes active and the platform positions itself back to the east.
In my example I have the light dividers about 2 inches long. If a tighter angular tolerance is desired the light dividers can be made longer.
Overall Layout.
The layout of the circuit has the CdS cells mounted on the eastern side of the board. The east/west, right ascension, pair is on the left. The north/south, declination, pair is on the right. The output power drivers are in the foreground.
I have mounted the power MOSFETs in such a way that they form the output terminals. Another example is pictured in my heliostat I/O board shown here: Terminals.
The PC board is all single sided using mostly 1/4 Watt resistors and capacitors mounted in surface mount fashion. This prototype construction technique is fast and easy to build. If the board is to be built in larger quantities a through hole board could be build with the parts in exactly the same location as the surface mount version.
(Any one want one? Email me at: <[email protected]>)
Here is my 1998 US cost breakdown in single quantities.IRF9Z34N $1.82 * 4 = $7.28 Digi-KeyIRFZ34N $1.25 * 4 = $5.00 Digi-KeyLM339N $ .49 * 1 = $0.49 Digi-Keyresistors $ .02 * 20 = $ .47 Digi-KeyPot D4AA15 $ .22 * 4 = $ .88 Digi-KeyCdS Cell $ .35 * 4 = $1.40 JamecoTotal $15.42
A true surface mount board using conventional, tiny, surface mount parts would make the board about 1/2 the present size. All the components are available in surface mount form except the CdS cells. Even the power transistors can be had in surface mount.
I don't think that the smaller sized board layout justifies the higher cost of the surface mount components.
Weather Dome.
How do you like the high tech weather dome? It is made of a 2 liter polyethylene plastic pop bottle. This plastic is pretty good in the UV of sunlight. Of course it can be easily replaced if it becomes clouded. Use the bottles with the black plastic base and remove it. The fancier Coka Cola bottles with the molded in feet don't work very well optically.
I think a 1 liter bottle would work just as well and the wooden mounting would be smaller. I haven't tried a 1 liter bottle yet.
The dome is not sealed from the weather in the picture. I will drill a hole in the wooden mount for the wires. The tapered sides to the wooden block will seal the dome to the block. The interior gets hot enough to vaporize any condensed moisture.
Experimental Goofy Demonstration Mount.
I needed a platform to test the circuit. I usually don't want to publish an untested circuit. I have had experience with circuits that don't operate as expected the first time. I sent Jeremiah a prototype, (Rev. A2), of the circuit and PC board to try out on his dish. Unfortunately he is moving his shop and couldn't try it out right away. I then decided to build a simple mount that I had been thinking about for a while.
This is a simple design meant for use with PV panels. It uses 2 satellite dish linear actuators. One to move the platform east and west about +-75°s in right ascension. The other to move the platform north and south a minimum of +/-23.5°s in declination.
The main pier is slanted to the south at an angle of 90° - the local latitude, (45°s for me). The reason the pier is tilted south is to align the right ascension axis to the polar axis which is the bolt that holds the ascension member to the pier. A second brace will be installed under the pier for support if needed.
Right Ascension / Declination Head.
This is a close-up of the mount head. The declination mechanism is controlled by the second satellite dish actuator. It tends to move the declination platform around the axis on the ends of the right ascension mechanism.
This picture shows the arrangement of the two satellite dish linear actuators. These actuators have adjustable limit switches. These switches are required by this circuit both to limit the travel and stop power from being wasted when at the limits.
Actuators with limit clutches are unsuitable for this application. While they do stop when the limit is reached, their motor continues to consume power. This is disastrous when running on a storage battery. The actuators, which consume over 10 amps, will drain the battery in a short while.
The magnitude of the declination movement is maximum when at the extremes of the right ascension and minimum in the middle of the travel range.
This design leaves a lot to be desired.
1. It has limited travel. 2. The declination angle changes in a complicated way with the movement of the right ascension angle. 3. It probably is not very strong when at the extremes of travel. I used it only as a convenient means of testing the analog controller.
patent5622078
Brad A. Mattson's Active Solar Tracker Patent# 5512742 & 5622078.
Brad's PV Solar Tracking Panel and Controller.
This is one of Brad's patents for this mechanism.
bradtrough
Brad's Trough Collector.
This is Brad's patent for the solar tracking controller.
shuntcharger
Solar Charge and Diversion Controllers.Most solar charge controllers are of the shunt type. They are easy to build and work very well. More complex controllers are the Maximum Power Point Controllers.
I will describe several circuits that are based on a Zetex ZM33064 computer voltage monitor and reset circuit. While there are a number of companies and models of voltage monitors on the market I chose the Zetex ZM33064 because of its low cost, accuracy, low power consumption, but mostly for the low, 20mV, hysteresis characteristic. Most reset circuits operate in a similar manner to the Zetex ZM33064 and could be substituted in the circuits.
I believe that power controllers based on voltage monitor circuits are significantly reduced in complexity due to the high integration of several power controller characteristics in a small 3 pin device that looks like an ordinary TO-92 transistor. In come cases it and a power MOSFET transistor are the only active devices in the circuit.
shunt1
A Simple Solar Shunt Charge Controller.
This is the simplest charge controller that I know of. OK, a really big zener is simpler but I don't know where to get one that can do the job. I have built several of these for different purposes and they work OK but I don't recommend there usage anymore because more advanced circuits exist today.
Shunt1Simple Shunt Charge Controller.
These parts can be obtained from: Digi-Key or Farnell. 5 Amp 40 Volt Diode $0.63us SB540CT-ND 51817712 Volt 1 Watt Zener Diode $0.26us 1N4742ADICT-ND 368660 1 Amp 50 Volt Diodes $0.60us/10 1N4001DICT-ND 36511710 Amp 25 Watt NPN Power Transistor Q1 $1.00us approximately7.5 Ohm 50 Watt Power Resistor RL $3.22us FVT50-7.5-NDTotal $5.17us
Of course you will also need a 25 watt heat sink for the transistor.
I don't know why but Digi-Key dropped their bipolar power transistors. You can get any NPN power transistor capable of dissipating 25 Watts possibly from Radio Shack.
This is a version of an amplified zener diode with a Schottky diode used to prevent power loss through the panel at night.
shunt2
A Better Solar Shunt Charge Controller.
Here's A better Solar Shunt Regulator. It can be made as large as you want. It's not as "simple" but it works better.
Shunt2Shunt Charge Controller.
These parts can be obtained from: Digi-Key or Farnell. 5 Amp 40 Volt Schottky Diode $0.63us SB540CT-ND 518177 5.1 Volt .5 Watt Zener Diode $0.21us 1N5231BMSCT-ND 368970 8.2 Volt .5 Watt Zener Diode $0.21us 1N5237BMSCT-ND 36902041 Amp 55 Volt Logic Level MOSFET Q1 $1.73us IRLZ44N-ND 637488 4.6 Volt ZM33064 Voltage Monitor $1.74us ZM33064C-ND 633318 1 K Ohm Trim Pot R2 $0.22us D4AA13-ND 2.0K Ohm .25 Watt 5% Carbon Film R1 $0.28us/5 2.0K E BK-ND24K Ohm .25 Watt 5% Carbon Film R3 $0.28us/5 24K E BK-NDTotal $4.86us
With Optional Heater Resistor
2 Ohm 100 Watt Resistor RL $12.45us AVT100-2.0-NDTotal $17.31us
Is this cheap enough?
How the Conventional Shunt Charge Controller circuit works.
This shunt regulator is based on a Zetex ZM33064 computer under voltage reset circuit.
The voltage monitor is an integrated circuit in a 3 pin package that in its normal usage is used to reset a microprocessor. The IN pin would normally be connected to a 5V logic bus.
When the 5V bus voltage drops bellow 4.6V the open collector OUT pin is pulled down toward ground.
In my circuit I use this output to switch the gate of a logic level power MOSFET.
When the voltage is bellow 4.6V the transistor is turned OFF and the PV panel is allowed to supply power to the battery until the voltage goes above 4.6V. The Zetex ZM33064 has a hysteresis of about 20mV which is degraded to 100mV in the circuit. This helps to prevent the power MOSFET from going into linear mode and dissipating power in the transistor. When in regulation the transistor will switch On and OFF at a rate dependent upon the capacity of the battery and power available from the PV panel.
The zener and resistors are used to divide the battery voltage down to the 4.6V range for the voltage monitor.
Don't skimp on the power MOSFET. You might ask why use a transistor capable of passing 41 amps in a circuit designed for only 5 amps. The answer is in the cost and complexity of the heat sink. This transistor has only .022 Ohms of ON resistance. This power dissipation at 5 Amps is:7 * 7 * .022 = 1.1 Watts. The transistor will get warm but not excessively and without a heat sink.
Of course if the full 41 amps is passing through the transistor then:41 * 41 * .022 = 37 Watts. This is significant and needs to be heat sinked for this amount of heat.
damage
Damage Your Panel With A Shunt Controller. Not!
You might ask if there is a problem with the direct shorting out of the PV panels?Will this shorting damage the PV panels?
The simple answer is NO!I have talked to several PV panel manufacturers. All have said that there are no detrimental effects to their panels.
Now for the more complex answer.One of the reasons that you might want to use the optional heater resistor instead of directly shunting the panel is that the panel will run slightly cooler, which is a good thing.
Think of it this way. when the panel is delivering it's peak load at a nominal efficiency of 15% much of the other 85% is dissipated as heat in the panel. If the panel is either open circuited or shorted then no power is delivered to the load and 100% of the influx is dissipated as heat in the panel. The shunt resistor, if selected properly, will have a voltage, not 0 volts, across it and dissipate nearly the same power that would have been delivered to the battery. The result is that the temperature of the panel will remain more constant.
OK, so this is only a minor point but I wanted to explain it thoroughly. I suspect that environmental conditions, such as clouds passing by, vary the temperature far more than that caused by any power regulator. Besides, the manufacturers say there isn't a problem here anyway.
I used the high current 41 Amp MOSFET because when operated at low currents it will dissipate only negligible power and prevent over heating.
The optional heater resistor can be used to heat something such as water or the house in winter. It's not needed. Normally the transistor dead shorts the panel. This is not an error. It's standard practice for solar panels to be shorted in this way. There is no harm to the panel doing this.
If you do use a large heat sink on the transistor this regulator is capable of much higher currents. Possibly as high as 41 Amps. (I haven't done this myself yet.)
The MOSFET power driver circuit probably should be improved for very high currents during regulation. The best improvement would be to use a D flip flop between the voltage monitor and the transistor gate. This flip flop is clocked at about 100 Hz. This will cause the transistor to have a controlled and predictable gate pulse.
shunt3
The Best Solar Shunt Charge Controller.
Here's the Best Solar Shunt Regulator. It's more complicated but it works better because it's temperature compensated.
I have adding temperature compensation to the basic shunt PV regulator. Temperature compensation is needed when the battery pack is stored in a location where the temperature is not controlled, such as outside and near the PV panel, in hot or cold weather.
Depending on the manufacturer, the charge voltage is adjusted by measuring the battery temperature. The specific value is mainly dependent on the internal RESISTANCE of the battery. This resistance is basically dependent on the CHEMICAL ACTIVITY in the battery. This chemical activity is dependent on the TEMPERATURE.
The construction methods can also affect the change in internal resistance vs. temperature.
temperature
Most lead acid batteries have a temperature coefficient somewhere between:-.0025 V/(°C * Cells) the minimum temperature coefficient.-.0036 V/(°C * Cells) being recommended by Bill Dubè if no other information is known.-.0040 V/(°C * Cells) being recommended by Hugh Piggott.-.0050 V/(°C * Cells) the maximum temperature coefficient.
13.8 Volt Lead Acid Battery Voltage vs. Temperature
°C °F LM50 Output -.0050 V/(°C * Cells) -.0040 V/(°C * Cells) -.0025 V/(°C * Cells)
50°C 122°F 0.900V 12.34V 12.75V 13.07V
25°C 77°F 0.750V 13.80V 13.80V 13.80V
0°C 32°F 0.500V 16.23V 15.55V 15.02V
-20°C -4°F 0.300V 18.17V 16.95V 15.99V
-40°C -40°F 0.100V 20.12V 18.34V 16.96V
Shunt3Temperature Compensated Shunt Charge Controller.
These parts can be obtained from: Digi-Key or Farnell. 5 Amp 40 Volt Schottky Diode $0.63us SB540CT-ND 518177 5.1 Volt .5 Watt Zener Diode $0.21us 1N5231BMSCT-ND 368970 5.1 Volt .5 Watt Zener Diode $0.21us 1N5231BMSCT-ND 36897041 Amp 55 Volt Logic MOSFET Q1 $1.73us IRLZ44N-ND 637488 4.6 Volt ZM33064 Voltage Monitor $1.74us ZM33064C-ND 633318 LM2902 Dual Operational Amplifier $0.49us LM2902M-ND 400002 -40°C to 125°C Temp Sensor $1.47us LM50CIM3-ND 630937 1K Ohm Trim Pot R7 $0.22us D4AA13-ND500K Ohm Trim Pot R8 $0.22us D4AA55-ND2.4K Ohm .25 Watt 5% Carbon Film R3 $0.28us/5 2.4K E BK-ND2.7K Ohm .25 Watt 5% Carbon Film R5 $0.28us/5 2.7K E BK-ND 10K Ohm .25 Watt 5% Carbon Film R4 $0.28us/5 10K E BK-ND 20K Ohm .25 Watt 5% Carbon Film R6 $0.28us/5 20K E BK-ND 91K Ohm .25 Watt 5% Carbon Film R1 $0.28us/5 91K E BK-ND200K Ohm .25 Watt 5% Carbon Film R2 $0.28us/5 200K E BK-NDTotal $7.26us
With Optional Heater Resistor
2 Ohm 100 Watt Resistor RL $12.45us AVT100-2.0-NDTotal $19.71us
How's that?! It's cheap and has temperature compensation too!
The bread boarding went well. I now have the circuit working. The LM2902 buffer Op Amp was required because the LM50 has a high impedance output. This output is not designed to drive even very low power powered loads.
The LM50C is a new generation SOT-23 part from National Semiconductor. It reads temperature from -40°C to 125°C. The interesting feature of this sensor is that it outputs 10mV per °C referenced to -50°C.
Vout=(10mV/°C*Temp°C)+500mV for the LM50C
Temp°C Temp°F Vout125°C 257°F 1750mV100°C 212°F 1500mV75°C 167°F 1250mV50°C 122°F 1000mV25°C 77°F 750mV0°C 32°F 500mV
-20°C -4°F 300mV-40°C -40°F 100mV-50°C -58°F 0mV
I mounted the LM50 on a little chip of PC board and soldered 3 wires to it. This allows the sensor to sample the battery temperature. To insulate the LM50 from possible damage I coated it with automotive "Oxygen Sensor Safe" RTV gasket cement from Permatex.
The .47uF capacitor is needed when the LM50 is mounted remotely with wires. It's not needed if the LM50 is mounted near the Op Amp on the PC board.
The two pots are very tricky to adjust because they interact with each other. The best way to set them is to substitute the LM50 with a voltage divider pot. It's also helpfully to substitute a resistor for the battery.
The LM50 makes it easy to substitute an external voltage for the LM50 temperature output voltage. Just force the desired voltage onto the output pin of the LM50 connected to the OpAmp. The LM50 has a high impedance resistor divider output. No damage will occur if the voltage is kept between -1VDC and VCC+.6VDC, +5.7VDC in this case. Of course the two calibration voltages will be .3VDC and .9VDC.
Temporary Test Circuit Used for Calibration.
Adjustment Procedure for Pots R7 and R8.
1. Determine which temperature coefficient you need from the manufacturers literature. 2. Introduce 0.300V, equivalent to -20°C, and adjust R8 for the correct output voltage. 3. Introduce 0.900V, equivalent to +50°C, and adjust R7 for the correct output voltage. 4. Repeat steps 2 and 3 until no more changes are needed to either R7 or R8.
I am not entirely satisfied with the circuit because of the sever interaction between the 2 pots when adjusting for different temperature coefficients. I think that one pot should be used to calibrate the sensor and the other to set the temperature coefficient with no interaction between them. I will consider a change in the future. Right now it works, don't fix it.
Right now the circuit is acceptable and works from -40°C to +50°C. I tested it in my temperature chamber. The circuit tracked quite well with temperature.
If you want the most accuracy possible you will have to calibrate the LM50. This is done by measuring the voltage output of the LM50 at two temperatures. Calculate the temperature coefficients for the sensor and introduce them into the standard equation.
Vtemp=(10mV/°C*Temp°C)+500mV
Use this new equation to get the true output voltage for -20°C and +50°C and use them in the R7 and R8 adjustment procedure.
If you want to purchase a commercial shunt controller check out the Morning Star units at:Windsunor:Natural Energy Systems, Inc.
undervoltage
Under Voltage Protection.
Damage to the battery or load equipment can occur if the storage battery charge is run down to much.
This could happen in many application such as these:
1. Sign Lighting. The battery could be under charged for the nights lighting requirements and could become depleted. 2. Remote
Instrumentation. The battery could be under charged if the weather has not allowed enough solar energy to accumulate. In this case critical measurement equipment could be left running while unnecessary equipment is turned OFF. In my case the Peet Brothers Ultimeter 2000 weather monitor remains ON while the Kenwood 7930 2 meter transceiver is turned OFF. The weather monitor continues to record data.
3. Water Pumping. In water pumping applications it is sometimes desirable to have the pump operate on a continuous basis, even at night. A storage battery supplies the night time power to run the pump. However, if the charge gets below 50% the battery life suffers. Under voltage cutoff protection can solve this problem.
4. Domestic Electricity.
The battery could be depleted due to excessive usage. In this case critical equipment, such as the computer, furnace, or refrigerator, could be left running while unnessassary equipment is turned OFF.
5. Sensitive Equipment.
Some equipment must be shut OFF when the battery voltage is low. My Kenwood 7930 2 meter transceiver doesn't tolerate low voltage well.
UndervoltageUnder Voltage Protection Circuit.
These parts can be obtained from: Digi-Key or Farnell. 8.2 Volt .5 Watt Zener Diode $0.21us 1N5237BMSCT-ND 369020 18 Volt .5 Watt Zener Diode $0.21us 1N5248BMSCT-ND 931688 -17 Amp -55 Volt P channel MOSFET Q2 $1.82us IRF9Z34N-ND 934677 .1 Amp 40 Volt NPN Transistor Q3 $1.60us/10 2N3904DICT-ND 358824 4.6 Volt ZM33064 Voltage Monitor $1.74us ZM33064C-ND 6333182.00K Ohm .25 Watt 1% Carbon Film R1 $0.54us/5 2.00K X BK-ND2.26K Ohm .25 Watt 1% Carbon Film R2 $0.54us/5 2.26K X BK-ND 10K Ohm .25 Watt 5% Carbon Film R9 $0.28us/5 10K E BK-ND 20K Ohm .25 Watt 5% Carbon Film RH $0.28us/5 20K E BK-ND 200K Ohm .25 Watt 5% Carbon Film R3 $0.28us/5 200K E BK-ND Total $4.52us
How the Under Voltage Protection circuit works.
This Under Voltage Protection Circuit is based on a Zetex ZM33064 computer under voltage reset circuit.
The voltage monitor is an Integrated Circuit in a 3 pin package that in its normal usage is used to reset a microprocessor. The IN pin would normally be connected to a 5V logic bus.
When the 5V bus voltage drops bellow 4.6V the open collector OUT pin is pulled down toward ground.
In my circuit I use this output to switch the Base of an NPN logic transistor, T3, which in turn operates the gate of a standard gate drive level P channel power MOSFET, T2.
The power transistor, T2, is turned ON when the battery voltage is higher than a set point and OFF when below the set point.
When the voltage is above 4.6V the output transistor is turned ON and the load is given power from the battery until the voltage goes below 4.6V. The Zetex ZM33064 has a hysteresis of about 20mV which is degraded to 100mV in the circuit. This helps to prevent the power MOSFET from going into linear mode and dissipating power in the transistor. This amount of hysteresis may not be enough for many applications.
An extra hysteresis resistor, RH, can be added to increase the hysteresis to higher voltages. This could be used to prevent cycling of the protected load. The amount of hysteresis required is dependent on the internal resistance of the battery. When the load is removed, due to low voltage, the battery voltage increases. If the hysteresis is not large enough the protected load will be turned ON again. And the cycle continues.
I can't give you an equation that predicts what this resistor should be. I can only suggest that you experiment with the value until satisfaction is obtained.
The two resistors, R1 and R2, are used to divide the battery voltage down to the 4.6V range for the voltage monitor. The hysteresis resistor, RH, affects this calculation.
Calculate the value of R2 for the Under Voltage Protection Circuit. Vc = 10.8V Desired cutoff voltage.Vm = 4.6V Threshold voltage of ZM33064.R1 = 2.00KOhms Lower voltage divider resistor.RH = 20.0KOhms Lower voltage divider resistor.Im = 180µA Quiescent current of ZM33064.R2 = ( Vc - Vm ) / (( Vm / ( R1
-1 + RH-1 )-1 ) + Im )
R2 = ( 6.2V ) / (( 4.6V / ( 1.8181KOhms ) + 180µA )R2 = ( 6.2V ) / (( 2.53mA ) + 180µA )R2 = ( 6.2V ) / ( 2.71mA )R2 = 2.29KOhmsR2 = 2.26KOhms Closest 1% value.WattsR2= ( Vc - Vm )2 / R2
WattsR2= ( 6.2V )2 / 2.26KOhms Calculate the power in R2
WattsR2= 0.017 Watts Use a 1/4 watt resistor.
I now have bread boarded this circuit and it works fine. I made a few changes to the circuit as published before. These were minor value adjustments. I also removed the adjustment pot. Next, I will make a PC board that includes the temperature compensated shunt regulator.
I have shown, on the schematic, two outputs:
1. Bypass. This output is for critical equipment. It essentially bypasses the protection circuits.
2. Protected. This output is for the equipment that can be turned OFF when the low battery voltage is reached.
I have added two optional jumpers:
J1 Enable Output. Enables normal operation of the controlled output. J2 Disable Output. Forces the controlled output OFF. None Output ON. J1 removed Forces the controlled output ON if J2 is not in place. J2, Disable Output, has precedence.
I hope that all of these designs will fulfill your needs. Obviously I can't know the specifics of your requirements. Please use general circuit design analysis to determine the proper size of the heat sink or the value and wattage of the optional heater resistance.
Use good judgement when sizing the power MOSFETs for higher power applications. I have attempted to use components that will work with much higher current MOSFETs. One caution is the use of logic level vs. conventional gate drive transistors.
The conventional gate drive transistors require that greater than 10 volts, some even higher, be applied to the gate to be fully turned on. Logic level gate drive transistors may be damaged by this high a gate voltage. Logic level gate drive transistors will be fully ON with 5 volts applied.
Power MOSFET characteristics:
Gate Drive. Logic Level Gate Drive Power MOSFETs Conventional Gate Drive Power MOSFETs Greater than 5 Volts.
Full rated current flow with low drive voltage. The transistor may be operating in the linear region which is usually very destructive.
Greater than 10 Volts.
The gate may breakdown with voltages greater than 10 volts.
Full rated current flow.
If you have any questions or special requirements about these circuits just send me an Email at:<[email protected]>
diversion1
Diversion Controller.
Here's A type of Shunt Regulator called a Diversion Controller. It can be used to dump unwanted charging power into a diversion load once the battery is full.
Diversion1Diversion Charge Controller.
These parts can be obtained from: Digi-Key or Farnell. 5.1 Volt .5 Watt Zener Diode $0.21us 1N5231BMSCT-ND 36897030 Amp 100 Volt Logic Level MOSFET Q1 $1.73us IRL540N-ND 740690 4.6 Volt ZM33064 Voltage Monitor $1.74us ZM33064C-ND 633318 1K Ohm Trim Pot RD $0.22us D4AA13-ND 2.00K Ohm .25 Watt 1% Carbon Film R1 $0.54us/5 2.00K X BK-ND24.3K Ohm .25 Watt 1% Carbon Film R2 $0.54us/5 24.3K X BK-ND24K Ohm .25 Watt 5% Carbon Film R3 $0.28us/5 24K E BK-NDTotal $4.17us
Is this cheap enough?
How the circuit works.
The diversion controller works similar to the shunt regulator. In the shunt regulator the source charging current is shunted to ground when the battery is full. In the diversion controller the diversion load is activated when the battery voltage is full.
The diversion controller has no charging diode and does have a diversion load.
This diversion controller is based on a Zetex ZM33064 computer under voltage reset circuit.
The voltage monitor is an Integrated circuit in a 3 pin package that in its normal usage is used to reset a microprocessor. The IN pin would normally be connected to a 5V logic bus.
When the 5V bus voltage drops bellow 4.6V the open collector OUT pin is pulled down toward ground.
In my circuit I use this output to switch the gate of a logic level power MOSFET.
When the voltage is bellow 4.6V the transistor is turned OFF and the diversion load is removed to allowed the power to the battery until the divided voltage goes above 4.6V. The Zetex ZM33064 has a hysteresis of about 20mV which is degraded to 100mV in the circuit for 12V.(I haven't built one of these but I would expect the hysteresis to be 400mV for a 48V battery.) This helps to prevent the power MOSFET from going into linear mode and dissipating power in the transistor. When in regulation the transistor will switch On and OFF at a rate dependent on the capacity of the battery and power available from the PV panel.
The two resistors, R1 and R2, are used to divide the battery voltage down to the 4.6V range for the voltage monitor.
Don't skimp on the power MOSFET. You might ask why use a transistor capable of passing 30 amps in a circuit designed for only 5 amps. The answer is in the cost and complexity of the heat sink. This transistor has only .044 Ohms of ON resistance. This power dissipation at 5 Amps is:5A2 * .044Ohm = 1.1Watts.The transistor will get warm but not excessively and without a heat sink.
Of course if the full 30 amps is passing through the transistor then:30A2 * .044Ohm = 40Watts.This is significant and needs to be heat sinked for this amount of heat.
The total diversion load in this example is:55.2V * 30A = 1656Watts.The diversion power can be increased by either using a larger transistor, paralleling more transistors, or paralleling more diverter controllers.
Additional diverters can be staged by setting them at slightly different voltages.
Calculate the Value of R2 in the Diversion Controller. Vc = 55.2V Desired Diversion voltage.Vm = 4.6V Threshold voltage of ZM33064.R1 = 2.00KOhms Lower voltage divider resistor.RD = 1KOhms Divider PotIm = 180µA Quiescent current of ZM33064.R2 = ( Vc - Vm ) / (( Vm / ( R1 + RD / 2 ) ) + Im ) - ( RD / 2 )R2 = ( 50.6V ) / ( 4.6V / ( 2.00KOhms + .5KOhms ) + 180µA ) - ( .5KOhms )R2 = ( 50.6V ) / ( 1.84mA + 180µA ) - ( .5KOhms )R2 = ( 50.6V ) / ( 2.02mA ) - ( .5KOhms )R2 = 25.05KOhms - ( .5KOhms )R2 = 24.55KOhms R2 = 24.3KOhms Closest 1% value.WattsR2= R2 * (( Vm / ( R1 + RD / 2 ) ) + Im )2
WattsR2= 24.3KOhms * 2.02mA2 Calculate the power in R2
WattsR2= 0.099 Watts Use a 1/4 watt resistor.
* Here is an Excel spreadsheet to do the math. http://www.redrok.com/DiversionController.zip
pwmmppt
Pulse Width Modulating, PWM, Solar Power Regulators.Maximum Power Point Controllers, MPPC.Maximum Power Point Trackers, MPPT.
The Maximum Power Point Tracker is a special form of buck/boost, sometimes buck only, power converter designed to deliver the maximum possible power to a load, or storage battery, from limited input power sources. These work similar to a normal Pulse Width Modulating, PWM, voltage regulator except that the pulse width control is designed to track the maximum power available from the PV panel. Of course, when the battery voltage is high enough then the converter is shut down effecting charge regulation.
PV panel output voltage, and consequently the maximum power point, varies in many ways. The maximum power point varies with temperature, light influx, cloud cover, dirt, and panel age. The important thing is that this maximum power point voltage rarely matches the battery voltage.
These converters are sort of reverse voltage regulators that instead of controlling the output voltage, which is fixed by the battery, controls the input voltage.
There are several ways to accomplish the control of this power conversion:
Fixed Ratio. The simplest way is to just manually set the pulse width of the power converter. While this is not technically a controller because the pulse width is fixed it does produce some power gain over a shunt controller.
Open loop power tracker.
A better way is to first characterize the panel voltage vs. the input light vs. output power. A photo sensor circuit controls the input voltage that the panel runs at. While these work reasonably well and more efficiently than the simple regulators they are not the optimum solution. In my opinion they are no cheaper to build than the better tracking circuit described next.
Closed loop power tracker.
More complicated and more accurate power tracking controllers use wattage sampling techniques to continuously find the optimal panel operating voltage. The way they work is to periodically introduce a small change in the controlled panel input voltage, measure the current, then calculate the input wattage. If the wattage has increased over the last sample then the next change in voltage should be in the same direction as the last change. However, if the wattage is less than the last sample then the next voltage change should be in the opposite direction to what the present change was.
The panel voltage is continuously being adjusted in a dynamic way to see if the output power can be increased. While the panel voltage is technically never at the true peak point the error is negligibly small. The result of this voltage dance is the ability of the controller to track the maximum power point no mater what the input PV panel conditions.
Can the circuit be made simpler? YES!
Closed loop current tracker.
It turns out that there is a major simplification in the control of maximum power point battery charger controllers. Delivered power is the multiplication of delivered current times battery voltage. Since battery voltage is relatively constant one needs to only use the delivered current to represent the approximate delivered power. No complex multiplication needs to be performed.
In the above example where power was used to determine the direction of the change of the input voltage The simplified controller uses the change of the delivered current sample as the clue for determining the direction of the change of the input voltage.
I built a controller for a windmill alternator in about 1973 that used OpAmps and CMOS logic gates. Today I think I would use a simple microprocessor to do the controlling.
Many micros have a built in AtoD converter and a PWM output. Use the AtoD to measure the output current and the PWM to control the pulse width of the pass transistor in the buck/boost converter.
Future Plans:
I am planning on designing an MPPT. I will be using a desktop PC as the logic element. I will use a simple buck circuit with the PWM controlled by the computer. A 1 bit integrating current sampling AtoD circuit will tell the computer if the power delivered is increasing or decreasing. The computer will always be slowly changing the pulse width wider or narrower. The direction of change is controlled by the polarity of the single bit AtoD.
I have done these experiments. I was successful.
I now plan to program a PIC micro processor to perform the function. The PIC I am interested in is the PIC12C672. This microprocessor is in an 8 pin dip. It has 4 A/D converters, an internal clock and is cheap. I hope this micro will do the job. I will keep you posted.
Any questions or comments? Email me at:<[email protected]>
For further study on how MPPTs work look at the various patents on the subject at my Neat Patents page:http://www.redrok.com/neat.htm#mppt
Conclusion:
If the power grid is available then there is no need of any form of PV nor other alternative power sources. The power grid provides a very stiff power source and can accommodate the use of simple low cost power supplies for most applications. However, not everyone has access to the power grid. Some also want that feeling of energy independence.
Conventionally, PV panels have been the mainstay alternative energy source. They are also very expensive. MPPTs are a solution to increasing the power delivered by the PV panels. If the costs of the MPPT is low enough, and I think they are, the total cost of the power delivered can be reduced.
MPPTs can benefit many applications where the input power is not very constant. Many alternative energy sources have highly compliant output power curves and require a more sophisticated power converter than a simple power supply. If one wishes to maximize the delivered power from highly compliant power sources MPPTs are what is required.
MPPT can increase the power output of a PV system by about 20%. Much greater gains in power can be obtained by using solar trackers which constantly aim the PV panels at the sun. I estimate about 100% increase in power output in summer and 50% increase annually, and about even in winter can be obtained from solar tracking.
The combination of solar tracking and MPPTs is an unbeatable combination.
If you want to purchase a good MPPT check out the Solar Converters, Inc. unit at:
windsun
Windsun, owned by Warren Lauzon.
solarconverters
Solar Converters Inc.
solarstar
SOLASTAR, Solar Powered Water Pumps.
rvproducts
RV Products, solar battery charging, monitoring, inverters and panels for your complete electrical independence!
Here is a circuit in the "Ideas For Design" column of Sep.14,1998 ELECTRONIC DESIGN.Maximum-Power-Point-Tracking Solar Battery Chargerby W. Stephen Woodward.
Here is an article from Feb.4,1999 EDN magazine.Harness solar power with smart power-conversion techniquesby Allan Petersen, Maxim Integrated Products.
PV to DC motor MPPTBuild this simple Mini Maximiserby Alan Hutchinson, Plasmatronics, MelbourneCircuit complete with PC board layout.
efficiency
Cost Efficiency in MPPTs, Maximum Power Point Controllers.
Now it can be argued that the cost of the MPPT controller is more expensive than adding an extra panel or 2 especially if it gains only about 20% over the shunt regulator. Also the MPPT is a single point of failure if only one is in the system.
This is a site to get the data to compare different collector types.
For my location in Minnesota I get:
2 axis flat plate June 8-10KWHr/m^2/day Flat Plate Tilted Lat+15 Deg June 4-5KWHr/m^2/day 2 axis flat plate Annual 6-7KWHr/m^2/day Flat Plate Tilted Lat Deg Annual 4-5KWHr/m^2/day 2 axis flat plate December 3-4KWHr/m^2/day
Flat Plate Tilted Lat-15 Deg December 3-4KWHr/m^2/day
If I weren't a tinkerer I don't think I would purchase one for my system. I think a solar tracking panel rack would be more cost effective. These can deliver double the power output in summer and 40% in winter instead of only a gain of 20% in efficiency as with an MPPT and it's cheaper to boot. Warren Lauzon points out that in the middle of winter when the flat plate tracking collector is about even with non tracking collectors the MPPT has the advantage.
