One area where in which microprocessor and microcomputers have a major impact is industrial processor control systems. Process control involves first measuring system variables such as motor speed, temperature, the flow of reactants, the levels of liquids in a tank, thickness of material etc. The output of controller then adjust the value of each variable until it becomes equal to a predetermined value called set point.

ANALOG PROCESS CONTROL Techo generator DC motor Set point

Disadvantages Over shoot problems. Over damping.

Microcomputer based process control system INPUT PORTS MICRO COMPUTER DAS solenoids OUTPUT Relays DAC KEYBOARD DISPLAY CONTROL SIGNALS TO DAS

TEMPERATURE CONTROL SYSTEM The temperature controller can be used to control the temperature of any plant. Typically it contains a Processor unit, Temperature input unit and Control output unit. The 8085 based motherboard forms the processing unit. The Analog-to-Digital unit together with temperature sensor forms the temperature input unit. The relay driver forms the control output unit. Electric power to the heating element (coil) is supplied through relay contacts. The switching ON/OFF of the relay controls the heat supplied to the plant. Operationally, the system requires two set points-upper and lower, to be entered by the user. Whenever the temperature of the plant exceeds the upper limit or recede the lower limit relay is turned-off, so that a temperature is maintained within limits. The software for the temperature controller is developed in 8085 assembly language programs.

TEMPERATURE CONTROL SYSTEM

HARDWARE DESCRIPTION: The hardware consists of 8085 microprocessor motherboard, ADC interface board, and relay and driver unit. The motherboard consists of 8085 MPU, 8KB EPROM, 8KB RAM keyboard and display controller 8279, programmable peripheral interface 8255, 21 key hex-keypad and six numbers of seven segment LED’s. Ports Expansion connector parallel port connectors are provided for external interfacing. The temperature input board or ADC interface board consists of ADC 0809, which is an 8-bit converter with eight channels of input. It is interfaced with the motherboard through 50-pin bus expansion connector. The temperature sensor ADC590 is used to sense the temperature of the plant and its analog output is applied to the channel-0 of ADC. Relay is switched ON/OFF by driving the transistor to saturation/cut-off which is connected to port A of 8255.

MP output ALE s/c EOC PC7 Port C lower Port c Upper Port A ADC 0808 Temperature sensor output voltage Vref IN 3 ABCABC 8255

Temperature vs. Vout T (C)Vin (mV)Vout(D7-Do)

Look Up Table MEMORY readings FD000A FD01OO FD02O1 FD03O2 FD04O3 FD05O4 FD06O5 FD07O6 FD08O7 FD09O8 FD0A09 MEMORY readings FE013F FE0206 FE035B FE044F FE0566 FE066D FE077D FE0807 FE097F FE0A6F FE0B

Program MVI A, 98H SEARCH INX H OUT 0BCMP M LOOP MVI A, 03H JC GO OUT 0AJZ GO MVI A, 0BDCR C OUT 0AJNZ SEARCH MVI A, 03 GOINR H OUT 0AMOV A,M READIN 0ASTA FFF6 RALCALL DISPLAY JNC READJMP LOOP IN 08 LXI H,FD00H MOV C,M

Stepper motor control 8085 Interface a Stepper Motor to the 8085 microprocessor system and write an 8085 assembly language program to control the Stepper Motor PA0 PA1 PA2 PA3 Stepper motor

Basic terminology for stepper motor STEP ANGLE :- Step is the minimum degree of rotation associated with a single step. STEPS PER REVOLUTION:- Steps per revolution may be defined as the total number of steps needed to complete 360̊ (e.g. 180 steps × 2 degrees = 360) steps per second and rpm relation steps per seconds = rpm ×steps per revolution/ 60

Program MVI A, 80H ;Initialize 8255 for port A as output. OUT CR MVI C, 32H : ;Set repetition count to 50. START: MVI B, 04H ;Counts excitation sequence LXI H, 6000H Initialize pointer BACK1:MOV A, M : Get the Excite code OUT PORTA Send Excite code CALL DELAY Wait INX H Increment pointer DCR B Repeat 4 times JNZ BACK l DCR C JNZ START

4 Step rotate sequence c Anti Clock wise rotation Clock wise rotation

Half step 8 Step rotate sequence StepW1W2W3W Clock wise rotationAnti Clock wise rotation

Traffic light system N S W E PC0 PC1 PC2 PB0 PB1 PB2 PA0 PA1 PA2 PC6 PC5 PC4

Traffic light system N S W E PC0 PC1 PC2 PB0 PB1 PB2 PA0 PA1 PA2 PC6 PC5 PC4

Traffic light system S E N W PC0 PC1 PC2 PB0 PB1 PB2 PA0 PA1 PA2 PC6 PC5 PC4 S E

Traffic light system N S W E PC0 PC1 PC2 PB0 PB1 PB2 PA0 PA1 PA2 PC6 PC5 PC4

Traffic light system N S W E PC0 PC1 PC2 PB0 PB1 PB2 PA0 PA1 PA2 PC6 PC5 PC4

Traffic light system N S W E PC0 PC1 PC2 PB0 PB1 PB2 PA0 PA1 PA2 PC6 PC5 PC4

Program MVI A, 80H ;CW for 8255 OUT 0B LOOP: MVI A, 01 OUT 09 ; Red on south OUT 08;Red on north MVI A, 44;Green on for east and west OUT 0A CALL DELAY1 MVI A, 22;Yellow on for east and west OUT 0A MVI A, 02 OUT 09; Yellow on for south OUT 08; Yellow on for north. CALL DELAY2 MVI A, 11 OUT 0A; Red on for east and west. MVI A, 04 OUT 08; Green on for north.

OUT 09; Green on for south CALL DELAY1 MVI A, 22 OUT 0A ; Yellow on for east and westMVI A, 02 OUT 09; Yellow on for south OUT 08 ; Yellow on for north CALL DELAY2 JMP LOOP