finnal diploma me 111 control project

Final Diploma Control Project ME 111

Higher Technological InstituteDepartment of Mechanical Engineering

Prepared by Dr. Mohiy E. Bahgat

Final Diploma Control Project

Mechatronics Final Control Project

1. Control projects :

The student can choose one of three projects :

1. Temperature control system.

2. Water level control system.

3. Pressure control system.

The three projects have the same control components, so, the control system

design will be discussed for the temperature control project as an example.

2. Temperature Control System :

The temperature control project block diagram is displayed in Fig (1) and (2).

Fig (1) - Closed loop temperature control system


Fig (2) - Temperature control system block diagram


Types of temperature sensors :

Thermistor RTD PT100 Thermocouple LM35

3. Objectives : To control the temperature of a fluid at any prescribed temperature

degree.

4. Introduction :

Temperature control is one of the basic control processes which use small

elements to achieve its concept. The main parts used among such a project

comprises :

Analog to digital converter ( ADC )

Such IC is used to convert analog signals into binary words. Figure (3)

shows the basic elements of the ADC. The procedure used is that a clock

supplies regular time signal pulses to the analogue to digital converter

and every time it receives a pulse it samples the analog signal. The result

of the sampling is a series of narrow pulses. A sample and hold unit is

then used to hold each sampled value until the next pulse occurs. See

figure (3). The simple analogue to digital converter is IC 0804 which

converts only one analog signal to digital one; the data sheet of its bin

description as it follows :

i) Chip Select (CS) : which is an input to activate the ADC 0804 chip.

Whenever this chip is to be functioned this CS input is activated. For


ADC 0804 chip select is an active low input. So whenever you want

ADC 0804 chip is to be function this pin is made low.

ii) Write (WR) : which is a control signal to tell the ADC chip to start

the conversion of analog data to binary format, it is an active low

input. When the Chip Select (CS) is at zero logic level, and a low to

high going pulse is applied to write pin of the ADC chip, chip starts

the conversion of the analog signal at its input terminal into 8-bit

binary output. The conversion hence depends on the input clock

(CLKIN) and CLKR inputs.

iii) CLK IN and CLKR : These two pins determines the conversion

time. When an external clock signal is applied for the timing CLK

IN pin is connected to the external clock signal. But there is an extra

feature in ADC 0804 chip. It has its own internal clock generator. If

someone wants to use this internal clock signal CLK IN and CLKR

are connected to resister and capacitor respectively. In this case the

clock frequency is calculated by : f = 1/ 1.1 RC Hz

where R is the resistance value and C is the capacitance value.

Normally we use R=10 KΩ and C=150 pF which are standard

values to get the frequency o 606 KHz with a conversion time of

110 micro seconds.

iii) Read (RD) : which is an input signal and also called output enable.

When the conversion completes the ADC chip 0804 stores the

converted data in its internal registers, to get this data as output, read

(RD) signal has to be applied. For this ADC chip RD is an active

low signal. When the data is to be read a low signal is sent to RD pin


keeping the CS pin low. The converted 8 bit data is available on the

output pins D0 to D7.

iv) Interrupt (INTR) : which is an output signal given by the ADC chip.

This signal is used as an input signal to microcontroller normally this

signal is at logic high. When the conversion completes the ADC

produces an active low interrupt signal. When this happens to read

the converted data the read signal is to be applied to ADC 0804

keeping CS signal low.

v) Vin (+) and Vin(-) : these are two differential analog input. The

effective Vin is Vin (+) ï؟½ Vin (-). Normally analog signal is

applied to Vin (+) keeping Vin (-) to ground. Vin should not be

exceeded than + 5V.

vi) Vref/2 : this is as reference voltage. To vary the range of signal

voltage this pin is used. This pin is kept at a potential deference half

of the Vin applied. The maximum Vin can be applied is + 5V. When

Vref/2 pin is kept open ADC reads to voltage from 0 to 5V.

vii) D0 to D7 : These are the 8 bit binary output pins of ADC 0804 chip.

ix) VCC : This is a power supply used for the proper functioning of ADC

chip. Normally this voltage is + 5v.

x) Ground (GND) : There are two ground pins in ADC chip representing

the analog ground and digital ground. Analog ground is connected to

the ground of analog signal source and digital ground is connected to

the ground of the Vcc source. This is done to isolate the analog in

signal from transient voltages caused by digital switching of the


output D0-D7 and for accuracy of the digital output of analog input

signal.

Fig (3) - Analog to digital conversion steps

The IC shape and bin description are shown in figure (4).


Fig (4) - ADC0804 bin description

Electrically erasable programmable read only memory (EEPROM) :

The EEPROM is one of the main types of programmable ROMS; which has

the ability to erase and rewrite individual bytes in the memory array

electrically During write operation. Internally circuitry erases all of the cells

at an address location prior to writing in the new data. This byte eras ability

makes it much easier to make changes in the data stored in an EEPROM.

The bin description is as follows :

The EEPROM has three control inputs determines the operating mode

according to table (1).


Table (1) - Ppin configuration

With CE=HIGH the chip is in its low-power standby mode, in which no

operation are being performed on any memory location and the data pins are

high.

To read the contents of a memory location, the desired address is applied to

the address pins; CE is driven low; and output enable pin OE is driven low to

enable the chip outputs data buffers. The write enable pin WE is held high

during a read operation.

To write into (a program) a memory location. The outputs buffers are

disabled so the data to be written can be applied as inputs to the I/O pins. To

begin write operation WE and CE are driven low; OE is driven high. The bin

description of EEPROM IC is shown in figure (5).


Fig (5) - Example of EEPROM IC AT28C16

BCD to 7- segment decoder

A decoder is a logic circuit that accepts a set of inputs that represents a

binary number and activates only the output that corresponds to that input

number. In other words, a decoder circuit looks at its inputs, determines

which binary number is present there, and activates the one output that

corresponds to that number; all other outputs remain inactive. The diagram

for a general decoder is shown in figure (6) with N inputs and M outputs.

Fig (6) - Decoder block diagram


a BCD-to-7-segment decoder/driver (7447) being used to drive a 7-segment

LED readout. Each segment consists of one or two LEDs. The anodes of the

LEDs are all tied to Vcc(+5 V). The cathodes of the LEDs are connected

through current-limiting resistors to the appropriate outputs of the

decoder/driver, See Fig (7).

Fig (7) - BCD to 7- segment decoder

Magnitude comparator

The 7485 IC is a 4-Bit Magnitude Comparator which compares two 4-bit

words (A, B), each word having four Parallel Inputs (A0–A3, B0–B3); A3,

B3 being the most significant inputs. The logic symbol is shown in Fig (8).

Fig (8) - Magnitude comparator pin configuration


Cascading inputs provide a means for expanding the comparison operation to

more than four bits by cascading two or more four-bit comparators.

If 8-bit words are used, the outputs of the first 4-bit comparator (low order bits)

are connected to the carry inputs of the second stage. The result of the overall

comparison is obtained from the outputs of the highest order 4-bit comparator,

whereby the appropriate output goes high. The cascading inputs should be

connected as shown in order for the comparator to produce the correct out puts;

figure (9).

Fig (9) - Two 7485 cascaded to perform an eight-bit


Isolation stage

OP-Amp is light D.C amplifier with gain ≈ 100,000. This stage is very

useful for isolation and ensure the signal will not have noise or decreases

with time. See Fig (10)

Fig (10) - OP-AMP pin description

It is a silicon chip which has

Inputs ( inverting and noninverting )

+ Voltage supply and - voltage supply

Two offset

One output

Depending on the connection of the Op-Amp the output may vary

Relay

Relay advantages

1) Switching high load with small voltage.

2) Complete isolation


The relay specified by

1) Relay coil voltage

2) Maximum current for the contact

There are many types of relays; the difference between them is the number

of contacts, voltage and ampere. As an example a five volt relay which has

to contacts one normally closed and the other is normally open; see figure

(2.11-a).

To connect the relay in any circuit; it is better to use switching circuit to

activate the relay coil as it shown in figure (2.11-b); when we apply voltage

value on the base of the transistor the transistor will be switched on and the

current will bass through the coil and the contacts will change there state.

Fig (11) - a) Relay pin description.

b) Relay connection in circuit


5. Part List :

Resistance (10kΩ Fixed, 2 x 1kΩ Fixed, 10kΩ Variable, 330Ω Fixed)

Capacitors (150 Pf)

7447 BCD to 7-segment decoder

7485 magnitude comparator

Board OPAMP

EEPROM ADC

Rozita Wires

TIP741 transistor Relay

LED

6. EEPROM calibration :

This part will discuss the procedure to make calibration for the EEPROM.

Table (2) - Temperature control calibration procedure

NO. Procedure

1 First connect the ADC input in a voltage divider circuit.

2 Then turn on the pump to supply the tank by water.

3 After that watch the ADC digital output and take the reading of the

temperature at each digital number appears in the output of the ADC.

4 Then after reaching a certain limit turn off the heater and power and

tabulate the readings.

Calibration results:-


Table (3) - Temperature control calibration results

Actual

Temperature

Temperature Binary code Equivalent

decimal code

25 25 01101100 54

30 30 01001100 50

40 40 00001100 48

50 50 01100100 38

51 51 00100100 36

52 52 01000100 34

54 54 00000100 32

65 65 01101000 22

67 67 00101000 20

70 70 01001000 18

74 74 00001000 16

91 91 01100000 6

After getting these results we should write it on Exedit program to write on the

memory the input output values. The procedure to use the EXedit program will be

as it shown in the next figures


7. Layout :

finnal diploma me 111 control project

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