AGMS

AUTOMATED GREENHOUSE MONITORING SYSTEM

BY

K.MAHESH

INTRODUCTION

BenefitsAutomatically control environmental conditions within greenhouse allowing any type of plants to be grown all year roundEliminates risk of greenhouse not being maintained at specific environmental conditions due to human errorMinimizes labor costs involved in maintaining a greenhouseCustomer able to define specific greenhouse conditions Plug-and play product

FeaturesDetect and maintain temperatures from -40C to 125CDetect and maintain humidity levels between 5% RH and 95% RHDetect sunlight and artificial light

Marketability / Business ProposalPresetting user-defined environmental conditions will allow company to have constant business with consumerConsumer requires company to recalibrate monitoring system yearly, as well as change preset environmental conditions if necessary Services can be performed in relatively short period of time, and at reasonably low price, thus not interrupting the monitoring systemIn most cases, consumers rarely change environmental conditions in the greenhouse, and therefore prefer the environmental conditions be preset

Automated Greenhouse Monitoring System

OBJECTIVE

Build miniature greenhouse which is equipped with automatic monitoring systemConstantly monitor environmental conditions in greenhouse to ensure it remains at preset temperature, light and humidity levels.

FunctionsLower Temperature: 2 Cooling FansRaise temperature: Heater (indicated by LED for demonstration purposes)Decrease humidity level: 2 Exhaust FansIncrease humidity level: Mister (indicated by LED for demonstration purposes)Increase lighting condition: Fluorescent Light-bulb

Miniature Greenhouse with Monitoring System

REVIEW ORIGINAL DESIGN

System OverviewVoltage output from sensors sent as inputs into PICBased on input values, PIC outputs specific voltages to turn ON/OFF devices

HardwareEnvironmental SensorsMicrocontrollerOscillatorEnvironment Maintaining DevicesTransistors & Relay

Ambient Light SensorManufacturer: Perkin Elmer Optoelectronics VTP-1188-SHOperating temperature: -20C to 75CWavelength Measurement Range: 400nm to 1100nmCurrent limiting circuit used to control current input into PIC:Voltage Operating Range of PIC: -0.3V to +7.5VMax Current into PIC VDD Pin: 25mAVOUT of Sensor: 0V to 1V Current Limiting: Use 50 resistor at output of sensor

Max IIN = 1V / 50 = 20mA

Temperature SensorManufacturer: Microchip Technology MCP9700A-E/TOOperating current: 6A to 12ATemperature Measurement Range: -40C to 125CDecoupling circuit to reduce noise from Power Supply:Connect +5V power supply to VDD pin using 200 resistor with 1F decoupling capacitorCurrent limiting circuit to control current input into sensor:V = IR: 5V / 6A = 833k 5V / 12A = 416.7kTherefore use resistor between 416.7k and 833kChose 680k resistorAllowable input current into PIC so connect directly to PIC: IOUT = 100A

Humidity SensorManufacturer: TDK Humidity Sensor Unit CHS-UGSOperating temperature: 5C to 45CHumidity Measurement Range: 5%RH to 95%RHCurrent limiting circuit used to control current input into PIC:Voltage Operating Range of PIC: -0.3V to +7.5VMax Current into PIC VDD pin: 25mAVOUT of Sensor: 0V to 1V Current Limiting: Use 50 resistor at output of sensor Max IIN = 1V / 50 = 20mA

MicrocontrollerManufacturer: Microchip PIC16F877AOperating Frequency: 20 MHzInput: Analog/Digital VoltageLow voltage requirement: +5VTotal Power Dissipation: 1.0WVoltage Operating Range: VDD = -0.3V to +7.5VMax Current into VDD pin: 250mAI/O Voltage Range: -0.3V to VDD + 0.3VMax Output Current by any I/O pin: 25mAAmbient temperature under bias: -55 to +125CAnalog to Digital conversion capability

OscillatorManufacturer: Fox Electronics F1100EFrequency: 20MHzVoltage: VDD = 5V

Devices2 Cooling FansHeater (LED)2 Exhaust FansMister (LED)LAMP OFF indicator (LED)Fluorescent Light-bulb

Transistors to Power Cooling Fans, Exhaust Fans & RelayPower supply: 5VRecommended Collector Current: 500mARecommended Base Current: 50mATransistors used as switches to provide 5V to connected devices. To ensure circuit functions properly, followed recommended current flow through resistor. To obtain required current flows, applied Ohms law and obtained current limiting resistor for collector to be 10 and 100 for the base. These specifications enable circuit to function properly

Relay to Turn ON/OFF Fluorescent Light-bulb DC voltage: 5VDC current: 500mA.Relay enabled AC current to flow by implementing a switch within the device which is controlled by DC currentThe relay supposed to allow AC current through when no dc current is flowingWhen DC current is passes through, relay will flick switch to ground, therefore causing open circuit for AC current flowApplied Ohms law to limit current flow and obtained limiting resistor to be 10

Circuit Diagram Schematic

PROJECT BUILD & FUNCTIONAL TESTS

Flow Chart

Testing of PIC using Function Generator & LEDsFunction generator used to simulate analog inputs of sensorsLEDs used to display appropriate output from PICExtreme cases such as voltage greater than or smaller than preset range testedPreset range of values for light, temperature and humidity tested, and function generator used to calibrate PIC inputCounter tested by checking time duration to output signal after one input is read

Modifying Preset Values for Greenhouse Environmental ConditionsPreset range can be modified by changing values of these variables: 1 ADC point equivalent to 4.883mV. int16 photoTRIGGER = 635; //

Testing of Cooling Fans & Exhaust FansPower supply: 5VMax current input: 800mACurrent driven into fan: 500mAReason: fan connected to transistor. For transistor, recommended collector current is 500mA. Therefore, use 500mA to power fansPIC will output 5V, thus use 100 resistor in order to limit current as recommended base current to be driven is 50mA. With this connection, fan functioned with sufficient power

Testing of Heater (LED), Mister (LED) & LAMP OFF (LED)Used LEDs to represent conditions in which heater and mister turned ONLED also used to signify situation where LAMP is OFF Voltage supply: 5VMax current input: 0.1AVoltage supply for LEDs supplied by output of PIC which will be 0V or 5 VTo supply correct current into LEDs, used current limiting resistorsFrom the Ohms law, V = IR, obtained current limiting resistor for LEDs:R = V / I = 5V / 0.1A = 50This specifications allows LEDs to function correctly

Testing of Fluorescent Light-bulbVoltage supply: 120VACTo use lamp, had to use a relay Relay controls current flow from power supply to light bulbRelay needs 5VDC with 500mA current flow to function as a DC/AC switch. Transistor will be used as a DC/DC switch to allow sufficient power to relayThe switching decision comes from PIC. When PIC outputs digital 0, lamp turns ON. When PIC outputs digital 1, lamp turns OFFVoltage equivalence of digital output 1 varies from 3.2V to 5V, and digital output 0 varies from 0V to 0.2V. When relay switch is flicked, 120V AC power for bulb will cut off since switch is thrown to connect with ground. Therefore, bulb turns OFF

SUCCESSES & CHALLENGES

Voltage & current inputs into PICVoltage input to PIC must be less than 6VTotal current entering PIC must not exceed 300mAMaximum current entering each pin must not exceed 25mACould damage PIC is not compliant

NoiseThermal sensor did not output values according to data sheetDue primarily to noise from power supply and surrounding noiseUsed decoupling capacitor circuit to minimize noiseSensor output values as expected

Programming of PICFirst 3 trial codes had issues with timerTimer problem fixed on fourth trial. Code was still not ready for multitasking (reading all 3 sensors at the same period and output desired signals from appropriate pins)Greenhouse monitoring system control successfully tested after sixth trial code. This code was implemented for demonstrationCode for seven segment display fully programmed but not fully tested

7-Segment DisplayInsufficient time for testing and calibratingPIC has insufficient ROM when compiling. Attempted to simplify code but determined that second PIC required for this purpose. After several attempts, simplified version of code is completedCode and logic is functional7-segment LED for double digits work as expected7-segment LED for single digit does not work as expected. Problem may be caused by Pin C output

Output Current from PIC to Power DevicesOutput current from PIC insufficient to turn devices onMaximum output from one pin is 20mA. Devices such as cooling fans, exhaust fans and relay (used as AC switch) required more currentProblem solved by using transistors

RECOMMENDATIONSKeep extra sensors in case (damaged humidity sensor be careful with connections)Keep extra PIC when programming. Chances of damaging PIC when programmingModify code line by line and test constantly (will help in debugging process)

SUMMARYProject successful; features described in Proposal functioned accordinglyEngineering knowledge acquired over the years fully applied and testedAcquired many new skills and knowledge; improved researching and trouble-shooting techniquesBelieve that product will be a success in the market as the Push for Green and environmental concerns intensifies in near future

CREDITSTHANK YOU:Professor: Gary SwensonTA: Tony MangogniaParts Shop PersonnelMachine Shop Personnel

QUESTIONS