1. Interfacing of LCD with µP
Temperature control using ADC
Interfacing of LCD with µP
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Temperature control using ADC

2. LCD (Liquid crystal display)
A liquid crystal display (LCD) is a thin, flat electronic visual display that uses the light modulating properties of liquid crystals (LCs).
Applications:-
Used in computer monitors , televisions , instrument panels, video players, gaming devices, clocks , watches, calculators , and telephones etc.
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Temperature control using ADC

3. Temperature control using ADC
Pin diagram of LCD
1.Vss – Gnd 2.Vcc - +5V 3.Vee - Contrast control 4. RS - Register select [RS=0: Command, RS=1: Data] 5. RW - Read / Write 6. EN - Enable pulse. 7. D0 - Data bus LSB 8. D D7 - Data bus MSB. 15 & 16 - Backlight.
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Temperature control using ADC

4. Temperature control using ADC
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Temperature control using ADC

5. Interfacing of ADC with µP
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6. 7/28/2018

7. ADC 0808
1. A, B, C addresses to select IN0-IN7 2. activate Address latch enable (ALE) to latch in the address. 3. SC is for Start Conversion. 4.EOC is for End of Conversion 5. OE is for Output Enable. 6. The output pins D0-D7 provides the digital output from the chip. 7. Vref (-) and Vref (+) are the reference voltages
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8. SELECTING AN ANALOG CHANNEL
How to select the channel using three address pins A, B, C is shown in Table below:
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9. Interfacing of ADC0808 with µP
Input to ADC0808-
SOC OE
A,B,C
ALE
Output for ADC0808-
EOC
D0-D7
PORT A - D0-D7(input) PORT B - SOC(PB0) - OE(PB1) - A,B,C(PB2,PB3,PB4) PORT C - EOC(PC0) CWR=99H Addresses for ports A,B,C and CWR=60H,61H,62H,63H
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10. Interfacing of ADC0808 with µP
PA0-PA7
D0-D7
ALE
PB0
PB1
PB2
PB3
PB4
SOC OE A B C
8255
ADC 0808
PC0
EOC
Clock generator
CLK
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11. The sequence and bit pattern required to give control signals
The sequence and bit pattern required to give control signals. The steps involved will be as: × C B A OE
SOC/ALE
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12. Program:-
JNZ UP MVI A,02H OUT 81H IN 80H OUT DISPLAY CALL DELAY MOV A,B ADI 04H MOV B,A JMP LOOP
MVI A,99H OUT 83H MVI B,00H LOOP: MOV A,B ANI 1CH ORI 01H OUT 81H UP: IN 82H ANI 01H CPI 01H
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13. Interfacing of DAC with µP
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14. Pin diagram of DAC AD7523
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15. Interfacing of DAC with 8255
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16. Pin description
The supply range is from +5V to +15V, while Vref may be any where between -10V to +10V.
The maximum analog output voltage will be any where between -10V to +10V, when all the digital inputs are at logic high state.
Usually a zener diode is connected between OUT1 and OUT2 to save the DAC from negative transients.
An operational amplifier is used as a current to voltage converter at the output of AD to convert the current out put of AD to a proportional output voltage.
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17. DAC AD-7523
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18. Program:- MVI A,80H Generate square wave :- OUT 83H UP: MVI A,00
CALL DELAY
MVI A,F0H
OUT 80H
JMP UP
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19. Generate Triangular wave:- MVI A,80H
OUT 83H
MVI B,00H
AGAIN: MOV A,B
UP: OUT 81H
CALL DELAY
INR B
MOV A,B
CPI FFH
JNZ UP
BACK :DCR B
MOV A,B
OUT 81H CALL DELAY CPI 00H JNZ BACK JMP AGAIN
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20. Generate saw-tooth wave:- MVI A,80H OUT 83H AGAIN: MVI B,00H JMP AGAIN
MOV A,B HLT
UP: OUT 81H
CALL DELAY
INR B
MOV A,B
CPI FFH
JNZ UP
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21. Temperature control using ADC
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Temperature control using ADC

22. Temperature control using ADC.
Flow chart .
START .
Initialize 8255
CALL CONVERSION
Turn heater on Is
Temp > SET Temp
Turn heater off
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Temperature control using ADC

23. Temperature control using ADC
Diagram
Temperature control using ADC
Sensor
Heater
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Temperature control using ADC

24. Temperature control using ADC
Control Word
The control word for the PPI is – i.e., 91H.
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Temperature control using ADC

25. Temperature control using ADC
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Temperature control using ADC

26. Temperature control using ADC
Program:
MVI A, 91H OUT CR BEGIN: CALL CONVERSATION CPI 41H JC NEXT MVI A, 0EH JMP BEGIN NEXT: MVI A, 0FH
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Temperature control using ADC

27. Conversion Subroutine:
CONVERSION: MVI A,00H OUT PB ; Send address to select IN0 MVI A,08H ;Latch address by giving ALE High OUT PB MVI A,18H OUT PB ; Make SOC High MVI A,08H OUT PB ; Make SOC Low OUT PB ; Make ALE Low LOOP: IN PC ANI 01H JZ LOOP ; Wait for EOC IN PA RET ; Return value and store Accumulator
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Temperature control using ADC

28. Temperature control using ADC
Interfacing Circuit
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Temperature control using ADC

29. Temperature control using ADC
The load, in this case a heater, is a device which operates under 230V ac.
The control signal from the microprocessor through the peripheral interface is of 5V magnitude.
A solid state relay device is used to interface the control signal with the load.
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Temperature control using ADC

30. Temperature control using ADC
Program:-
MVI A,91H OUT 03 L2: CALL CONVERSION CPI 80H JC L1 MVI A,0EH OUT CWR JMP L2 L1: MVI A,OFH
SUBROUTINE conversion : MVI A,00H OUT PB MVI A,08H MVI C,0AH L3: DCR C JNZ L3 MVI A,18H L4: IN PC ANI 01H JZ L4 IN PA RET
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Temperature control using ADC