AUTOMOTIVE ELECTRICAL AND

ELECTRONICS Lab

LAB MANUAL

B.Tech

DEPARTMENT OF AUTOMOBILE ENGINEERING

BHARATH INSTITUTE OF HIGHER EDUCATION AND RESEARCH

173, AGARAM MAIN ROAD, SELAIYUR, CHENNAI - 600073

Department of Automobile Engineering

U18LCAU4L1 - AUTOMOTIVE ELECTRICAL AND

ELECTRONICS Lab

LIST OF EXPERIMENTS

AUTOMOTIVE ELECTRICAL LAB

1. Battery testing

2. Alternator testing.

3. Starter motor testing

4. Diagnosis of ignition system.

5. Diagnosis of automotive electrical wiring.

6. Fault finding of relay & fuses in car using Off Board Diagnostics Systems (OBDS).

7. Relay & fuse Fault diagnostic of a car using OBDS

AUTOMOTIVE ELECTRONICS LAB

1. Characteristics of rectifiers and filters

2. Study of IC timer

3. Study of Microprocessor 8085

4. Simple ALP program using 8085 MEL Kit

5. Data acquisition from sensors using 8085 MEL Kit

6. Interfacing of stepper motor with 8085 MEL Kit

7. Fault finding location of sensor in car using OBDS

Department of Automobile Engineering

U18LCAU4L1 - AUTOMOTIVE ELECTRICAL AND ELECTRONICS Lab

1. TESTING OF BATTERIES & BATTERY MAINTENANCE

AIM:

To conduct specific gravity test and open voltage test of the given battery used in automobile and

find the state of charge.

APPARATUS REQUIRED:

1. Battery.

2. Hydrometer.

3. Voltage tester.

DESCRIPTION:

The battery is an electrochemical device. It uses chemical to produce electricity. The amount of

electricity it can produce is limited. As the chemical in the battery is depleted, the battery runs

down and is discharged. It can be recharged by supplying it with electric current from the vehicle

alternator or from a battery charger. The depleted chemicals are restored to their original

condition as the battery becomes charged.

The automotive battery supplies electric current to operate the starting motor and ignition system

while starting the engine. It also acts as a voltage stabilizer by supplying current for the lights,

radio and other electrical accessories when the alternator is not handling the load. In addition, the

battery supplies a small amount of current to the volatile memory in the electronic control

module while the ignition key is off. The specific gravity test and the open voltage test are

conducted to find out the state of charge in the battery. Load test is performed to find out the

battery condition.

PROCEDURE:

BATTERY VISUAL INSPECTION:

A cranked cover on a top terminal battery may result from using the wrong wrench to turn the

nut on the cable clamp bolt. Over tightening the hold down clamps may crack the case. Over

tightening the cable bolts in side-terminal batteries may pull the terminal loose.

On vent-cap batteries, remove the vent caps check the electrolyte level. Add water if needed.

CLEANING THE BATTERY:

Top-terminal batteries may corrode around the terminals and clamps. Disconnect the cables and

clean the terminals and clamps with a battery-terminal brush. Brush the battery top with a

solution of baking soda with water. After the foaming stops, flush off the battery and top with

water. To retard corrosion, coat the terminals with anticorrosion compound

TESTING THE BATTERY:

Testing determines if the battery:

1. Is in good condition.

2. Needs recharging.

3. Is defective and should be discharged.

Batteries are tested in two ways: for state of charge and for performance. The state of charge of a

vent- cap battery is determined with the hydrometer. The built in hydrometer or charge indicator

is maintenance- free battery provides this information. An open circuit voltage test can be used.

The battery- load test indicates if the battery is capable of performing its job.

OPEN CIRCUIT VOLTAGE TEST:

1. Open circuit voltage of the battery is measured with the help of an ordinary voltmeter.

2. Connect the terminals of the battery across a voltmeter and find out the voltage supplied by the

battery.

3. The voltmeter reading represents the battery state of charge. If the voltage is below 12.40

volts, charge the battery.

HYDROMETER TEST:

The float hydrometer is used in the same way. It will float in the electrolyte drawn in. marks on

the float stem show the electrolyte specific gravity. This indicates the state of charge. The more

fully charged the battery, the higher float. The relationship among specific gravity and open

circuit voltage are same in all conditions of battery.

1. This test is conducted with the help of hydrometer.

2. Open the vent gap of the battery and immerse the sampler tube of the hydrometer in the cell

electrolyte.

3. Squeeze the rubber bulb and release the same which would cause a sample of the electrolyte to

be drawn inside the glass body.

4. Now the float inside will rise and note down the surface level of the sample drawn in.

5. The value represents the specific gravity of the electrolyte from which the state of charge of

the battery can be known.

6. If the hydrometer test shows less than 0.050 differences between the various cells, charge the

battery and if the value is more than 0.50, replace the battery.

BATTERY LOAD TEST:

1. After a battery passes charge test, it is tested for load test.

2. This test measures the terminal voltage of battery while it is discharging at a high rate.

3. The test is performed with a load tester that includes a voltmeter, ammeter and loading device.

4. Apply 15 A load for 15 seconds. This is done to remove any surface charge present in battery.

5. Then apply a load equal to half the CCA and note the voltage and condition of the battery.

6. If the voltage is below 9.6 volt, recharge the battery and retest it. A battery that fails the load

test a second time is defective.

BATTERY MAINTENANCE TIPS:

The life of a battery, apart from its original design and valid use, depends to a large extent on the

attention which is given for its proper maintenance. The battery maintenance includes making a

visual inspection of the battery, cleaning the battery top terminals and cable clamps and testing

and charging the battery.

1. Look for signs of electrolyte leakage, cracks in the case or top, missing vent caps, and loose or

missing hold-down clamps. On a side-terminal battery, check for loose terminals and leaking

electrolyte. Leakage causes white corrosion on the battery fray and surrounding metal.

2.Remove the vent plugs, taking care that no flame is brought near the vents as the gas inside is

highly inflammable and check for electrolyte level in the battery cell. In case the electrolyte level

in the battery is not sufficient, top up with distilled water.

3. If water topping requires frequently, investigate the reason for this. This may be due to over-

charging which may be avoided by setting the regulator properly.

4. Top terminal batteries may corrode around the terminals and clamps. Disconnec t the cables

and clean the terminals and clamps with a battery terminal brush. Brush the battery top with a

solution of baking soda and water. After the foaming stops, flush off the battery top with water.

To retard corrosion, cat the terminal with anti-corrosion compounds like Vaseline or petroleum

jelly. Never use grease.

5. Never let the battery in discharged condition. This will lead to sulphation of the battery plates

and damage the battery.

The following table shows the relation between battery’s state of charge and its specific gravity

Specific Gravity ( Cold and Temperate)

State of Charge Specific Gravity (Tropical)

1.265 100 % 1.125

1.225 75 % 1.185

1.190 50 % 1.150

1.155 25 % 1.115

1.120 Dead 1.080

The open circuit voltage and battery’s state of charge:

RESULT:

Thus the specific gravity test, open voltage test and a load test were conducted and the state of

charge was found for the given battery.

1. The state of charge as found by specific gravity test is --.

2. The state of charge as found by open voltage test is --.

3. Battery voltage from load test --.

4. The condition of the battery found from load test --.

Open circuit voltage test:

Voltage State of Charge

12.6 – 12.9 Fully charged

12.2 Half charged

Below 11.9 Fully discharged

Sl.No Voltage Condition of battery

Specific gravity test:

Cell no Specific gravity of electrolytes Condition of battery

1.

2.

3.

4.

5.

6.

High discharge test:

Sl.No Battery Voltage before cranking

Battery Voltage after cranking

Load test:

Sl.No

Voltage (v)

condition

good weak bad

2. TESTING OF STARTER MOTOR AND ALTERNATOR

AIM:

To test the given alternators and starter motor which are used in automobile.

APPARATUS REQUIRED :

1. Test Bench

2. Voltage Tester

3. Alternator

4. Digital Tachometer

5. Battery

6. Starter Motor

DESCRIPTION:

ALTERNATOR:

The alternator converts mechanical energy from the engine into electrical energy. It is usually

mounted on the side of the engine. The engine crankshaft pulley drives the alternator through a

belt at two or three times the crankshaft speed. A regulator in the alternator prevents the

alternator from producing excessive voltage. Some manufacturers call the alternator a generator

or a.c generator. The alternator restores the charge to the battery and also handles the load of the

ignition, lights, radio and other electrical and electronic equipments while the engine is running.

The speed of the generator at which its output voltage just rises above voltage of the battery

being charged is called cutting- in speed.

TESTS CONDUCTED ON ALTERNATOR :

1. Alternator performance characteristics.

2. Alternator output test.

3. Cut- in and cut-out voltage of alternator.

PROCEDURE:

1. The alternator is mounted on the test bench and the connections are made. Alternator is

connected to battery and to the test bench.

2. The drive to the alternator is given by means of a variable speed electric motor.

3. With proper connections and the alternator is not running, the charging indicator in the test

bench remains on. This indicates that the battery is not charging.

4. Start the electric motor and allow the alternator to rotate at slow speed. The alternator speed is

measured by means of a tachometer. When the alternator rotates at low speed, the output voltage

value is zero and the charge indicator lamp remains on.

5. Gradually increase the speed of alternator. With increase in speed, the output voltage

increases. At a particular speed, the voltage reaches a steady value and the charge indicator lamp

goes off. This is the cut- in speed of the alternator. Note down the alternator speed and voltage.

Also note the current value at that condition.

6. To conduct the performance test, the alternator is brought to zero speed. Gradually increase

the alternator speed from zero RPM to the rated speed by varying the motor speed. For each

speed, note down the current and voltage output produced by the alternator. Plot a graph with

speed along X-axis and voltage & current along Y-axis and check whether it matches with

manufacturer’s specification.

7. To find out the cut-off speed of the alternator, the alternator speed is reduced gradually from

the rated speed and at a particular speed, the charge indicator light gets on is known as the cut-

off speed of alternator. Note down the voltage and current at that stage. The voltage indicates the

cut-off voltage of alternator.

8. To conduct the alternator output test, the alternator is made to run at the rated speed and the

load is applied to the alternator. By applying the load and maintaining the alternator speed

constant, check whether it produces the rated current and voltage as specified by the

manufacturer.

STARTER MOTOR:

To start the engine, the crankshaft must turn fast enough for air- fuel mixture to enter the

cylinder. An electric starter or starting motor does the job. It converts electrical energy from the

battery into mechanical energy that rotates the crankshaft. When the driver turns the ignition key

to start, the control circuit causes contacts to close in a starter relay or solenoid switch. High

current then flows from the battery to the starter motor. As the starter motor shaft turns, it turns

the crankshaft fast enough to start the engine.

TESTS CONDUCTED ON STARTER MOTOR :

1. No load test.

2. Current draw test.

PROCEDURE:

NO LOAD TEST:

1. Starter motor is firmly mounted on the test bench. Better supply is connected to the

starter motor and ammeter and voltmeter are connected across the battery to measure the

current and voltage drawn by motor.

2. Turn on the ignition key and find out the voltage and current drawn by the battery. Also

note down the motor speed. Check whether the reading obtained are as per the

manufacturer’s specification. If not, find out and rectify the fault.

CURRENT DRAW TEST:

1. This test measures the current flow to the starter motor while it cranks the engine.

2. Disable the ignition coil and connect ammeter to the battery cable.

3. Turn ignition key to start and read the current draw and note down it. Check whether it is

according to manufacturer specification. If not, find and rectify the fault

RESULT:

Thus the given alternator and starter motor are tested and the results are tabulated

Full load:

Speed

Load

voltage

No load:

Speed

Load

Voltage

Voltage – drop test:

Connections

Voltage (v)

Cable 1

Cable 2

Battery + ve terminal

Battery – ve terminal

Ignition switch

Cable 1-battery to switch

Cable 2-battery to starter motor

Cut – off voltage:

Speed

Voltage

3. DIAGNOSIS OF IGNITION SYSTEM FAULTS

AIM:

To diagnose the fault in the ignition system of engine.

APPARATUS REQUIRED :

1. Multimeter

2. Feeler gauge

3. Battery

4. Lamp

5. Screw Driver

6. Spark plug tester and ignition coil tester.

PROCEDURE:

If the engine does not start after cranking, check for fuel in the fuel system and its faults. If the

fuel system is found to be correct, then check the ignition system.

TO CHECK PRIMARY CIRCUIT:

Remove the distributor cap and take out the rotor. See that the contact breaker points are opening

and closing freely. Check the contact breaker gap with a feeler gauge and it should be around

0.35 -0.40 mm. Adjust the gap if necessary.

TO CHECK THE SECONDARY CIRCUIT:

The major defects in the secondary circuit are likely to occur in spark plug distributor cap and

rotor, H.T leads and ignition coil.

1. To spot the fault, remove the H.T lead from one of the spark plug. Place its ends about 10 mm

from the engine block. With the ignition on, crank the engine. If the spark jumps across the gap

regularly and with good intensity, then the entire secondary circuit up to and including the

distributor is working alright and any fault could lie in the spark plug.

2.To check if there is any problem in the spark plug, remove one spark plug from engine and

check for any carbon deposit between the electrode gap. If there is any carbon deposit, clean the

plug and adjust the electrode gap before using.

3. If there is no carbon deposits, connect H.T lead from the distributor to this spark plug and

place the plug on the cylinder block. Now crank the engine and notice the spark from plug. If the

plug produces a blue spark of high intensity, the pug is alright and if not, check the plug for

correct electrode gap or fit a new plug and check it. If the spark occurs, then the fault is with

spark plug.

4. When even placing the H.T lead about 5 mm from the cylinder, if a spark of good intensity is

not obtained, then the fault must be either in the distributor or in the coil.

5. Remove the distributor gap and check for corrosion in the rotor tip and condition of carbon

brushes. If there is any fault, change it. If it is alright, then the fault might be with ignition coil.

6. To check the ignition coil, remove it from the vehicle. Connect the positive and negative

terminals of ignition coil to an ignition coil tester and the H.T lead is connected to the spark plug.

On pressing the cut-off button in the tester, if a blue spark of good intensity jumps across the

spark plug, then the coil is in good condition. If not, replace the coil with a new one.

OPERATING PROCEDURE:

1. Give connections as detailed in the assembly of parts. Check all the connections are given

properly.

2. Using the knob in D.C controller unit, set the rpm to the idle (800 rpm) by adjusting the knob

and rpm can be measured in the display provided in the timing light.

3. Measure the timing angle (Mark on the disc must match with the pointer on the cabinet) by

adjusting knob provided in the timing light. Press the MODE switch to measure the dwell angle

and note the values in the tabular column. (A sample tabular column is attached).

4. Increase the rpm with an increment of 100 every time and measure the timing angle and dwell

angle using the step-3.

5. Using the same procedure using the vacuum pump connected, measure the dwell and timing

angle.

Testing at 800, 900, 1000, 1500 RPMs are good speed to test the distributor and always run the

test from slower to higher RPM to get the better results.

CAUTION:

Hold the secondary cable with insulated pliers made up of non conductive material .Do not metal

pliers with insulated handles.

RESULT:

Thus the fault in the ignition system is diagnosed and the engine is started.

Without Vacuum

Engine RPM Dwell angle Timing angle

Engine RPM Dwell angle Timing angle

Engine RPM Dwell angle Timing angle

Spark plug and contact breaker point test:

Color of spark :

Spark plug gap :

Contact breaker point gap :

4. WIRING OF HEAD LIGHT, TRAFFICATORS, AND ELECTRIC HORN

AIM:

To check the wiring of head light, trafficators, electric horn and replacing if not wired properly

and draw the circuit of given model.

APPARATUS REQUIRED:

1. Wire cutter.

2. Wire stripper.

3. Screw driver.

4. Wires.

5. Multimeter.

6. Battery.

7. Automotive electrical component set-up.

PROCEDURE:

1. The insulation part of the wire is stripped using wire stripper.

2. Then insert it into the holes of switches and give connections as shown in the wiring diagram.

3. Check the fuse in fuse box and replace it if it is not proper.

4. Check the connections to the battery so that there is no short circuit.

5. Tighten the screw of switches and replace it and relays by the screw driver to avoid loose

connections.

6. Switch on the lights and see the brightness, if correct and horn is working, Check for

trafficators are working and correct deviation is shown , if not check the wiring or change the

fuse. In case of trafficators check toggle switch and flasher.

7. While checking turn off supply as a safety measure.

8. Check the relays so that more amount of current doesn’t flow in the cut out is proper.

9. At last check the ignition switch and dim dipper switch control.

RESULT:

Thus the wiring of head light, trafficators and electric horns are checked and circuit diagram is

drawn.

5. Characteristics of rectifiers and filters

AIM: To study the characteristics of half wave, full wave with and without filter

EQUIPMENT REQUIRED:

Diodes, Resistor, Transformer, Voltmeter, Ammeter, Breadboard and CRO

THEORY:

Rectifier changes ac to dc and it is an essential part of power supply. The unique property of a

diode, permitting the current to flow in one direction, is utilised in rectifiers.

Half Wave Rectifier

Mains power supply is applied at the primary of the step-down transformer. The entire positive

half cycles of the stepped down ac supply pass through the diode and all the negative half cycles

get eliminated. Peak value of the output voltage is less than the peak value of the input voltage

by 0.6V because of the voltage drop across the diode.

For a half wave rectifier,

Vrms= Vm/2 and Vdc=Vm/π:

where Vrms= rms value of input,

Vdc= Average value of input and

Vm= peak value of output.Ripple factor r =Vr,rms/Vdcwhere

Vr,rmsis the rms value of the ac component. Since

Full Wave Rectifier

The diode D1 conducts and current flows through load resistor RL. During negative half cycle,

diodeD2 becomes forward biased and D1 reverse biased. Now, D2 conducts and current flows

through the load resistor RLin the same direction. There is continuous current flow through the

load resistor RL, during both the half cycles and will get unidirectional current as show in the

model graph. The difference between full wave and half wave rectification is that a full wave

rectifier allows unidirectional (one way) current to the load during the entire 360 degrees of the

input signal and half-wave rectifier allows this only during one half cycle (180)

CIRCUIT DIAGRAMS:

Half wave rectifier with filter:

Full wave rectifier with filter

WAVEFORMS

Typical waveforms of half wave rectifier without filter and with filter are shown in the figure

below

RESULT: Thus study was the characteristics of half wave, full wave with and without filter

6. Study of IC timer AIM:

To study IC timers as: 1. Astable multivibrator, 2. Mono stable multivibrator

IC 555 TIMER:

The 555 timer is widely used as IC timer circuit and it is the most commonly used general

purpose linear integrated circuit. It can run in either one of the two modes: Monostable (one

stable state) or Astable (no stable state). In the Monostable mode it can produce accurate time

delays from microseconds to hours. In the Astable mode it can produce rectangular waveforms

with a variable Duty cycle. The simplicity and ease with which both the multivibrator circuits

can be configured around this IC is one of the main reasons for its wide use. Design of an

Astable multivibrator using 555 timer IC, generating non-sinusoidal waveform in the form of

Rectangular waveform as well as capacitor voltage waveform in the form of ramp waveform.

Block diagram of 555 Timer IC:

The block diagram of a 555 timer is shown in the figure. A 555 timer has two comparators

(which are basically Two op-amps), an R-S flip-flop, two transistors and a resistive network.

The Resistive network consists of three equal resistors (5K Ohms each R) and acts as a

voltage divider. Notice that the resistor network is designed in such a way that the voltage at the

Inverting terminal of Comparator 1 (Upper comparator) will be 2/3Vcc and the voltage at the

Non Inverting terminal of Comparator 2 (Lower comparator) will be 1/3Vcc. Comparator 1 –

compares the threshold voltage (at pin 6) with the reference voltage + 2/3 VCC volts.

Comparator 2 – compares the trigger voltage (at pin 2) with the reference voltage + 1/3 VCC

volts. In most applications, the control input is not used, so that the control voltage equals +(2/3)

VCC. Upper comparator has a threshold input (pin 6) and a control input (pin 5). Output of the

upper comparator is applied to set (S) input of the flip-flop. Whenever the threshold voltage

exceeds the control voltage, the upper comparator will set the flip-flop and its output is high. A

high output from the flip-flop when given to the base of the discharge transistor saturates it and

thus discharges the transistor that is connected externally to the discharge pin 7. The

complementary signal out of the flip-flop goes to pin 3, the output. The output available at

pin 3 is low. These conditions will prevail until lower comparator triggers the flip-flop.

Even if the voltage at the threshold input falls below (2/3) VCC that is upper comparator cannot

cause the flip-flop to change again. It means that the upper comparator can only force the flip-

flop’s output high. To change the output of flip-flop to low, the voltage at the trigger input must

fall below + (1/3) Vcc. When this occurs, lower comparator triggers the flip-flop, forcing its

output low. The low output from the flip-flop turns the discharge transistor off and forces the

power amplifier to output a high. These conditions will continue independent of the voltage on

the trigger input. Lower comparator can only cause the flip-flop to output low. From the above

discussion it is concluded that for the having low output from the timer 555, the voltage on the

threshold input must exceed the control voltage or + (2/3) VCC. This also turns the discharge

transistor on. To force the output from the timer high, the voltage on the trigger input must drop

below +(1/3) VCC. This turns the discharge transistor off. A voltage may be applied to the

control input to change the levels at which the switching occurs. When not in use, a 0.01 nF

capacitor should be connected between pin 5 and ground to prevent noise coupled onto

this pin from causing false triggering. Connecting the reset (pin 4) to a logic low will place a

high on the output of flip-flop. The discharge transistor will on and the power amplifier will

output a low. This condition will continue until reset is taken high. This allows

synchronization or resetting of the circuit’s operation. When not in use, reset should be tied to

+VCC. You can see the output wave forms in the side diagrams. The two important

parameters that we should understand from the output of timer is ON Time (THIGH=T1) and

OFF Time (TL0W=T2)

RESULT: Thus the study IC timer was studied

Aim: Study of architecture of microprocessor 8085

Internal Architecture of 8085 Microprocessor

Control Unit

Generates signals within uP to carry out the instruction, which has been decoded. In reality

causes certain connections between blocks of the uP to be opened or closed, so that data goes

where it is required, and so that ALU operations occur.

Arithmetic Logic Unit.

The ALU performs the actual numerical and logic operation such as ‘add’, ‘subtract’,‘AND’,

‘OR’, etc. Uses data from memory and from Accumulator to perform arithmetic. Always stores

result of operation in Accumulator.

Registers

The 8085/8080A-programming model includes six registers, one accumulator, andone flag

register, as shown in Figure. In addition, it has two 16-bit registers: the stackpointer and the

program counter. They are described briefly as follows. The 8085/8080A has six general-purpose

registers to store8-bit data; these are identified as B,C,D,E,H, and L as shown in the figure. They

can be combined as register pairs -BC, DE, and HL -to perform some 16-bit operations. The

programmer can use these registers to store or copy data into the registers by usingdata copy

instructions.

Accumulator

The accumulator is an 8-bit register that is a part of arithmetic/logic unit (ALU). This register is

used to store 8-bit data and to perform arithmetic and logical operations. The result of an

operation is stored in the accumulator. The accumulator is also identified as register A. FlagsThe

ALU includes five flip-flops, which are set or reset after an operation according to data

conditions of the result in the accumulator and other registers. They are called Zero(Z), Carry

(CY), Sign (S), Parity (P), and Auxiliary Carry (AC) flags; they are listed in the Table and their

bit positions in the flag register are shown in the Figure below. The most commonly used flags

are Zero, Carry, and Sign. The microprocessor uses these flags to test data conditions. For

example, after an addition of two numbers, if the sum in the accumulator id larger than eight bits,

the flip-flop uses to indicate a carry --called the Carry flag (CY) –isset to one. When an

arithmetic operation results in zero, the flip-flop called the Zero(Z) flag is set to one. The first

Figure shows an 8-bit register, called the flag register, adjacent to the accumulator. However, it

is not used as a register; five bit positions out of eight are used to store the outputs of the five

flip-flops. The flags are stored in the 8-bit register so that the programmer can examine these

flags (data conditions) by accessing the register through an instruction These flags have critical

importance in the decision-making process of the microprocessor. The conditions (set or reset) of

the flags are tested through the software instructions. For example, the instruction JC (Jump on

Carry) is implemented to change the sequence of a program when CY flag is set. The thorough

understanding of flag is essential in writing assembly language programs. Program Counter

(PC)This 16-bit register deals with sequencing the execution of instructions. This registeris a

memory pointer. Memory locations have 16-bit addresses, and that is why this is a16-bit register.

The microprocessor uses this register to sequence the execution of the instructions. The function

of the program counter is to point to the memory address from which the next byte is to be

fetched. When a byte (machine code) is being fetched, the program counter is incremented by

one to point to the next memory location.

Stack Pointer (SP)

The stack pointer is also a 16-bit register used as a memory pointer. It points to memory location

in R/W memory, called the stack. The beginning of the stack is defined by loading 16-bit address

in the stack pointer. The stack concept is explained in the chapter "Stack and Subroutines."

Instruction Register/Decoder

Temporary store for the current instruction of a program. Latest instruction sent here from

memory prior to execution. Decoder then takes instruction and ‘decodes’ or interprets the

instruction. Decoded instruction then passed to next stage. Memory Address Register

Holds address, received from PC, of next program instruction. Feeds the address bus with

addresses of location of the program under execution.

Control Generator

Generates signals within uP to carry out the instruction which has been decoded. Inreality causes

certain connections between blocks of the uP to be opened or closed, sothat data goes where it is

required, and so that ALU operations occur.

Result: Thus the study of Architecture of 8085 microprocessor was completed.

8. Simple ALP program using 8085 MEL Kit AIM

Addition of two 8-bit numbers.

Apparatus Required: 8085 Simulator, PC.

Program:

Result:

Thus the program to add two 8 bit numbers was executed.

9. Interfacing of stepper motor with 8085 MEL Kit

AIM: -To study the stepper motor and to execute microprocessor computer based control of the

same by changing number of steps, the direction of rotation and speed.

APPARATUS USED:- Stepper Motor Kit, μP Kit, Interface Cord and Connecting Leads.

THEORY:-The stepper motor is a special type of motor which is designed to rotate through a

specific angle called step for each electrical pulse received from its control unit. It is

used in digitally controlled position control system in open loop mode. The input command is

in form of a train of pulses to turn the shaft through a specified angle. the main unit is designed

to interface with μP 8085 kit. The stepper motor controller card remains active while the pulse

sequence generator disabled as given plug is connected with μp interface socket . Following

programme enables the stepper motor to run with μp 8085 kit. For two phase four

winding stepper motor only four LSB signals are required.

CIRCUIT DIAGRAM:

ROCEDURE:-

Connect the stepper motor with μp 8085 kit as shown in fig. press EXMEM key to enter the

address as given then press NEXT to enter data.

ADDRESS DATA

Press FILL to save data. to execute the programme press the key GO .The above

programme is to rotate the motor at a particular as defined by the given address. Changing the

following contents will change the motor speed.

RESULT:- The stepper motor runs as per fed programme.