A project on automated harness tester

7/29/2019 A project on automated harness tester

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Chapter – 1

INTRODUCTION

1.1 INTRODUCTION TO AUTOMATED HARNESS TESTER

Automated Harness Testers are used in military ,navy and aerospace having

electronic sub-systems to find the defective or miswired cables instantly before they

damage equipment or waste valuable technician time. Perform high speed electrical

interconnect testing on cables and harnesses for wiring correctness and insulation

quality.

Speed, ease-of-use & product reliability are ensured through key features including:

Test a 100 point net in under 1 minute for wiring correctness

Circuit continuity tests for open circuits.

Insulation resistance verification for short circuits.

Dielectric breakdown or hi-pot tests.

High voltage tests.

Start testing immediately with menu-driven operator screens

Serialize and save the results in universal „.txt‟ format for SPC analysis and

reporting

Faulty End Recognition tool identifies wiring faults and their physical location

in the product.

This tester are fast, accurate and easy to use and saves a lot of time involved in

manual checking. Automated harness testers have a unique, patented graphic display to

pin-point problems when wiring errors are detected, and offer one

second pass/fail testing for production environments. Quickly locate intermittent-

connections and identify their position in the cable.



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Figure 1.1: THE AUTOMATED HARNESS TESTER

The system comes with the capability to chek up to 128 test points for large

Cables and wiring harnesses, and measure cables of up to 100 feet in length.The system

has also 79 pin , 55pin, 9 pin mounts embedded within the system to check the

connectivity of various other cables .

With our Model cable tester, set two resistance thresholds, one for good

Connections down to 0.5 ohms, and one for isolation up to 10 Megohms. Measure

embedded resistors and resistor networks, and check the orientation of diodes. Choose

from a wide variety of plug-in connector boards to mate with most standard cables, and

easily mount custom connectors for unusual applications

The easy-to-use software can be set up for one-button operation to speed

production testing. Unskilled operators need only to press the TEST pushbutton on the

Fixture to trigger an involved test sequence set up by the quality control engineer, with



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results automatically logged to disk for later analysis and report generation. Use an

optional footswitch for hands-free operation.

For complex wire harnesses and multi-headed cables, label each pin with

your own custom text to speed the location of faulty connections. Harness testers like to

the pc using a serial port like rs232 standard. More than just cable and harness testing-

equipment, our wiring analyzers verify continuity, insulation/resistance, hipot and even

perform functional testing of relay chassis, control panels and other assemblies with

components.

You don‟t have to be a programmer to use the automated harness tester.The

easy to use control program steps you through a series of choices.This menu-driven

system keeps operations simple without sacrificing the functionality or flexibility you

nedd while running a test.This flexibility is essential in your test system so yo can meet

your specific requirements even when they change.

1.2 NEED FOR THE SYSTEM

The existing system involves the manual checking of each and every pin of a

connector. In this method the person directly uses the multimeter to check the

connections of continuity and short. This method has several disadvantages as it

consumes a lot of time and also much possibility of occurrence of errors again and

again.

As it is very much difficult to check out the connectivity of all pins manually

we go for the “Automated Harness Testing” which executes the testing process in

fraction of seconds. It performs high speed electrical interconnect testing for wiring

connection and insulation quality.

This system is very much useful to the industries having electronics sub

system to find the defective of miswired cables instantly before they damage the

equipment or waste valuable technician time. This system are compulsory required for

fault debugging and physical checking of connectors before they are used. This devices

are mainly used in medical, aviation, medical and industrial market.



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Chapter – 2

REQUIREMENTS

2.1 HARDWARE REQUIREMENTS

The automated harness tester requies a number of hardware components.The

description of each component and number of quantities used is clearly specified below.

2.1.1 Relays

In this system we use a SPST 2A Non Latch Relay.A total no.of 256 such relays are

used.

2.1.2 Relay drivers

The automated harness tester equipment uses 16 pin SOIC Relay driver.We use 37

such drivers in this system.

2.1.3 Microcontroller

This system uses a 8051 microcontroller.

2.1.4 CPLD

This system uses a Complex Programmable logic device (CPLD) manufactured by

CYPRESS company.

2.1.5 Diodes

The automated harness tester uses 256 diodes to control the relays.

2.1.6 Multimeter

Here in this system we use a two – wired multimeter to check the connectivity of cables.

2.1.7 RS-232

We use two rs232 communication ports to communicate the data within the system.



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2.1.8 Test computer

In this system we use a test computer to provide the inputs and to view the obtained

results.

2.1.9 Chassis Mounts

In this automated harness tester we use a various types of chassis mounts to

meet the requirements of various cables. The different chassis mounts used in this

system are shown below.

128 Pin Male chassis mount

128 Pin Female chassis mount


55 Pin Male chassis mount



9-Pin Male St PCB mount

2.2 SOFTWARE REQUIREMENTS

In this system we use a Microsoft visual 2005 with c++ source coding. The

easy-to-use software can be set up for one-button operation to speed production testing.

Unskilled operators need only to press the RUN button on the fixture to trigger an

involved test sequence set up by the quality control engineer, with results automatically

logged to disk for later analysis and report

generation.



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Chapter – 3

LITERATURE SURVEY

3.1 EXISTING METHOD/SYSTEM:

The existing system involves the manual checking of each and every pin of a

connector. In this method the person directly uses the multimeter to check the

connections of continuity and short. This method has several disadvantages as it

consumes a lot of time and also much possibility of occurrence of errors again and

again. This method can take long hours or even many days to check the wholeconncectivity.The existing method involves much complexity and even there‟s a lot of

confusion to the person checking it.Sometimes repetitive checking occurs due to the

lack of concentration in the work.The generation of report in this method is too tough

because the total work has to be done manually and usually it consumes a lot of

valuable time.

3. 2 THE PROPOSED SYSTEM

As it is very much difficult to check out the connectivity of all pins manually

we go for the “Automated Harness Testing” which executes the testing process in

fraction of seconds. It performs high speed electrical interconnect testing for wiring

connection and insulation quality.It finds the defective of miswired cables instantly

before they damage equipment of waste valuable technician time.Speed of ease and

product realiability are ensured through key features including the checking of more

than 500 test points in less than one minute.

In our project we are including checking of test points upto a maximum of

128 pins.This system also performs the connectivity tests for the conectors having 9,55

and 79 test points as per the equipment requirements.Automated Harness Tester consists

of micro controller based system and switching console as required by the number of

test points.In the proposed system starts the testing process immediately with menu-

driven operator sceens.This system also serialize and save the result in the universal

„.txt‟ format future analysis.



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The system comes complete with the capiblity to perform…

Circuit continuity tests for open circuits

Insulation resistance verification for short circuits

Dielecrtric breakdown(hi-pot) tests

Resistors, diodes and capacitor tests.

The automated harness tester has several adavantages over the existing method

like….

The time consumption in this method is far less than that of the

existing method.It consumes only a few minutes to perform the

whole operation.

The possibility of occurrence of errors are almost low since the

process is automated .

This method is fast, accurate and easy to use and we can also perform

checking/verification of more number of points.

It also checks high voltage problems applied to the circuit/device.



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Chapter – 4

BLOCK DIAGRAM ORGANISATION

The block diagram organization reveals the brief overview of the project

automated harness tester.It describes the connection of one component with the other

and here we are studying each component of the block diagram in depth.By knowing

the block diagram organization we can clearly get the idea of how each component in

the system works and we will also get known that whats the input to the system and the

corresponding generated output.

4.1 BLOCK DIAGRAM OF AUTOMATED HARNESS TESTER

Figure 4.1: Block diagram of Automated Harness Tester



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4.2 MAIN COMPONENTS OF BLOCK DIAGRAM

The main components of the block diagram are

The Switching block

The control block

The multimeter

A RS-232 communication port

A test computer

4.2.1 THE SWTICHING BLOCK

The Switching block comprises of 256 relays.In our project we have used the

SPST 2A Non Latch realay.The relay is a single-pole single-through switch.

A relay is an electrically operated switch. Many relays use an electromagnet

to operate a switching mechanism mechanically, but other operating principles are alsoused. Relays are used where it is necessary to control a circuit by a low-power signal

(with complete electrical isolation between control and controlled circuits), or where

several circuits must be controlled by one signal. The first relays were used in long

distance telegraph circuits, repeating the signal coming in from one circuit and re-

transmitting it to another. Relays were used extensively in telephone exchanges and

early computers to perform logical operations.

Latching and non-latching describe the mechanism used to actuate/de-

actuate electromechanical coils. To change the state of a latching relay (open/closed), a

short pulse is sent to the set or reset lines on the relay. For non-latching relays, a

constant source is required to maintain the 'on' position. Removing power from a non-

latching relay (also referred to as failsafe relays) will return the contacts to their 'normal'

or power-on state. Removing power from a latching relay will not affect the present

state of the contacts (i.e., the contacts maintain their position at the time that power is

removed).

http://en.wikipedia.org/wiki/Electric

http://en.wikipedia.org/wiki/Switch

http://en.wikipedia.org/wiki/Electromagnet

http://en.wikipedia.org/wiki/Electromagnet

http://en.wikipedia.org/wiki/Switch

http://en.wikipedia.org/wiki/Electric



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Latching relays should be used when an application requires one or more of

the following:a)The last state of the relay prior to power removal must be maintained.

b) Thermal stability through power management. Because latching relays are pulsed to

activate, there is minimal quiescent current draw while measurements are being made.

Non-latching relays require constant current, and will radiate heat that may affect

critical-measurements.

c)Better repeatability. Latching relays generally ensure more repeatable contact closures

with regards to insertion loss over the life of the relay. Variations in insertion loss from

closure to closue can affect critical measurements.

Non-latching relays should be used when an application requires one or more

of the following:

a) Cost is a factor. In general, latching relays will be less expensive than their latching

equivalents.

b) Relays need to be set to their normal position when power is removed. In normal

operation, power removal is planned and handled elegantly. However, when power loss

is not planned, it may be desirable, considering safety, to force the configuration of the

box into its normal/power-on state.

RELAYS

■ What Are Relays?

To get an idea of what relays are, think of a children's athletic carnival.

The baton is the signal.

Figure 4.2:An example describing relays



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Little A holds on tightly to the baton and passes it to the Big B. This is a relay.

Figure 4.3: The inside of a SPST RELAY

Now lets look at a more technical example.Think of tuning on a television with a

remote control.

Figure 4.4:Working of Relay



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Principle of Operation of Relays

In this example, we will turn ON a lamp using switch S1 and a relay.

Press S1 to turn it ON.

Current i flows to the operating coil and magnetizes the core.

The armature is drawn to the core by the electromagnetic force.

When the armature reaches the core, the moving and fixed contacts make

contact and the lamp lights.

When S1 is released to turn it OFF, current no longer flows to the operating coil,

the electromagnetic force no longer exists, and the armature returns to its

original position by the force of the release spring.

When the armature has returned to its original state, the contacts become

separated and the lamp turns OFF.

In our project we are using OMRON SPST 2A Non latch Relay.Below is the

image of the above realay.

Figure 4.5: Omron relays used in the project



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Extremely tin SPST_No Flat Relay,one of the thinnest relay in the world

Uses 20% less mounting area and 67% less volume in comparision with

the G5V-1 realy. Measures just 7.0 (W) x 10.6(L) x 4.5(H) mm for surface-mount or 4.1

(H) for through – hole.

High dielectric strength :1,000 VAC between coil and contacts and 750

VAC between contacts of the same polarity.

Conforms to FCC Part 68.

UL recognized /CSA certified.

RoHS Compliant-Use of Lead completely eliminated.

Application examples

Peripherals of modem or PC

Telephones

Office automation machines

Audio-visual products

Communication equipment

Measurement devices

Amusement equipment

Security equipment

4.2.2 CONTROL BLOCK

The control block consist of microcontroler based system and control bus. It is

the main block of the project. It controls the whole operation of the system. Control

block is an interface between switching block and the Test computer. RS 232 interface

is used to establish the communication between these components.



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4.2.2.1 MICROCONTROLLER BASED SYSTEM

In this project we are using 8051 microcontroller.

INTRODUCTION TO 8051 MICROCONTROLLER

A microcontroller is a computer with most of the necessary support chips

onboard. All computers have several things in common, namely:

A central processing unit (CPU) that „executes‟ programs.

Some random-access memory (RAM) where it can store data that is

variable.

Some read only memory (ROM) where programs to be executed can be

stored.

Input and output (I/O) devices that enable communication to be established

with the outside world i.e. connection to devices such as keyboard, mouse,

monitors and other peripherals.

There are a number of other common characteristics that define

microcontrollers. If a computer matches a majority of these characteristics, then it

can be classified as a „microcontroller‟. Microcontrollers may be:

„Embedded‟ inside some other device (often a consumer product) so that

they can control the features or actions of the product. Another name for a

microcontroller is therefore an „embedded controller‟.

Dedicated to one task and run one specific program. The program is

stored in ROM and generally does not change.

A low-power device. A battery-operated microcontroller might consume

as little a 50 milliwatts.

A microcontroller may take an input from the device it is controlling and

controls the device by sending signals to different components in the device. A

microcontroller is often small and low cost. The components may be chosen to

minimise size and to be as inexpensive as possible.The actual processor used to

implement a microcontroller can vary widely.



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In many products, such as microwave ovens, the demand on the CPU is

fairly lowand price is an important consideration. In these cases, manufacturers

turn to dedicated microcontroller chips – devices that were originally designed to

be low-cost, small, low-power, embedded CPUs. The Motorola 6811 and Intel

8051 are both good examples of such chips.

A typical low-end microcontroller chip might have 1000 bytes of ROM

and 20 bytes of RAM on the chip, along with eight I/O pins. In large quantities, the

cost of these chips can sometimes be just a few pence.

The predominant family of microcontrollers are 8-bit types since this

word size has proved popular for the vast majority of tasks the devices have been

required to perform.The serial ASCII data is also byte sized making data

communications easily compatible with the microcontroller devices. Because the

type of application for the microcontroller may vary enormously most

manufacturers provide a family of devices, each member of the family capable of

fitting neatly into the manufacturer‟s requirements. This avoids the use of a

common device for all applications where some elements of the device would not

be used; such a device would be complex.The figure below shows the Phillips P89V51RD2 microcontroller which is

used in our project.

Figure 4.6: PHILIPS 8051 MICROCONTROLLER



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P means the device is manufactured by Philips Semiconductors

8 means the micro belongs to the 8-bit 8051 family

9 means Flash code (program) memory

Philips P89V51RD2 Microcontroller

The P89V51RD2 is a 80C51 microcontroller with 64 kB Flash and 1024

bytes of data RAM. A key feature of the P89V51RD2 is its X2 mode option. The design

engineer can choose to run the application with the conventional 80C51 clock rate (12

clocks per machine cycle) or select the X2 mode (6 clocks per machine cycle) to

achieve twice the throughput at the same clock frequency. Another way to benefit from

this feature is to keep the same performance by reducing the clock frequency by half,thus dramatically reducing the EMI.

The Flash program memory supports both parallel programming and in serial

In-System Programming (ISP). Parallel programming mode offers gang-programming

at high speed, reducing programming costs and time to market.

ISP allows a device to be reprogrammed in the end product under software

control. The capability to field/update the application firmware makes a wide range of

applications possible.

The P89V51RD2 is also In-Application Programmable (IAP), allowing the

Flash program memory to be reconfigured even while the application is running.

Features

80C51 Central Processing Unit

64 kB of on-chip Flash user code memory with ISP (In-System Programming)

and

IAP (In-Application Programming)

Supports 12-clock (default) or 6-clock mode selection via software or ISP

SPI (Serial Peripheral Interface) and enhanced UART

PCA (Programmable Counter Array) with PWM and Capture/Compare

functions

Four 8-bit I/O ports with three high-current Port 1 pins (16 mA each)



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Three 16-bit timers/counters

Programmable watchdog timer

Eight interrupt sources with four priority levels

Second DPTR register

Low EMI mode (ALE inhibit)

TTL- and CMOS-compatible logic levels

Brown-out detection

Low power modes

of Power-down mode with external interrupt wake-up

Idle mode

DIP40 packages

Figure 4.7: Architecture of 8051

The P89C66x family of microcontrollers have four 8-bit ports: port 0, port

1, port 2 and port 3.

Traditionally in the 80C51 family of microcontrollers the function of port

0 and port 2 is primarily to allow for connection to an external PROM (code



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memory chip). Port 0 provides both the 8-bit data and the lower 8 bits of the

address bus, A0 to A7. Port 2 provides the upper 8 address bits, A8 to A15. All of

the flash microcontrollers referred to in this text have onboard code memory, which

can be as much as 64 KB.

Port 0 pins are all from open-drain transistors and the port pins should

have pull-up resistors (e.g. 2.7 k~ from pin to 5 V DC supply) if the port is to be

used as a general-purpose interface.

Port 3 has some special function pins, e.g. pins 0 and 1 of port 3 may be

used as receive and transmit for the UART

PIN CONFIGURTION OF 8051

PIN 9: PIN 9 is the reset pin which is used to reset the microcontroller‟s internal

registers and ports upon starting up. (Pin should be held high for 2 machine cycles.)

PINS 18 & 19: The 8051 has a built-in oscillator amplifier hence we need to only

connect a crystal at these pins to provide clock pulses to the circuit.

PIN 40 and 20: Pins 40 and 20 are VCC and ground respectively. The 8051 chip needs

+5V 500mA to function properly, although there are lower powered versions like the

Atmel 2051 which is a scaled down version of the 8051 which runs on +3V.

PINS 29, 30 & 31: As described in the features of the 8051, this chip contains a built-in

flash memory. In order to program this we need to supply a voltage of +12V at pin 31.

If external memory is connected then PIN 31, also called EA/VPP, should be connected

to ground to indicate the presence of external memory. PIN 30 is called ALE (address

latch enable), which is used when multiple memory chips are connected to the controller

and only one of them needs to be selected.We will deal with this in depth in the later

chapters. PIN 29 is called PSEN. This is "program store enable". In order to use the

external memory it is required to provide the low voltage (0) on both PSEN and EA pins



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Figure 4.8: Pin diagram of 8051

PORTS OF 8051

There are 4 8-bit ports: P0, P1, P2 and P3.

PORT P1 (Pins 1 to 8): The port P1 is a general purpose input/output port which can

be used for a variety of interfacing tasks. The other ports P0, P2 and P3 have dual roles

or additional functions associated with them based upon the context of their usage.

The port 1 output buffers can sink/source four TTL inputs. When 1s are written to

portn1 pins are pulled high by the internal pull-ups and can be used as inputs.

PORT P3 (Pins 10 to 17): PORT P3 acts as a normal IO port, but Port P3 has

additional functions such as, serial transmit and receive pins, 2 external interrupt pins, 2

external counter inputs, read and write pins for memory access.

PORT P2 (pins 21 to 28): PORT P2 can also be used as a general purpose 8 bit port

when no external memory is present, but if external memory access is required then

PORT P2 will act as an address bus in conjunction with PORT P0 to access external

memory. PORT P2 acts as A8-A15, as can be seen from fig 1.1



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PORT P0 (pins 32 to 39) PORT P0 can be used as a general purpose 8 bit port when no

external memory is present, but if external memory access is required then PORT P0

acts as a multiplexed address and data bus that can be used to access external memory in

conjunction with PORT P2. P0 acts as AD0-AD7, as can be seen from fig 1.1

PORT P10: asynchronous communication input or Serial synchronous communication

output.

4.2.2.2 CONTROL BUS

The control bus is a common bus which connects the microcontroller to the

relays through I/O ports.The I/O ports are connected to CPLD.The CPLD is a Complex

Programmable Logic Device it is connected to the control bus . CPLDs typically have

the equivalent of thousands to tens of thousands of logic gates, allowing implementation

of moderately complicated data processing devices.

4.2.3 TWO-WIRED MULTIMETER

A multimeter is a device used to measure electrical properties such as

voltage, current and resistance. A multimeter is a multi function device that works as aVoltmeter, Ammeter and Ohmmeter.The common multimeter is a small handheld

device with an indicator needle over a measurement scale or a numeric LCD display.

The device has a switch to select the type of test to be performed. A multimeter also has

two wires, one red (+) and one black (-), with metal tips. They are called probes.

In this project a special digital mutltimeter is designed to meet the

requirements of the device.The positive and negative probes of the multimeter are

conncected to the switching block.The results obtained in the digital multimeter are sent

to the test comuter through a rs-232 communication port for report generation and

future analysis.

http://en.wikipedia.org/wiki/Logic_gate





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Below figure is showing the digital multimeter used in the project

Figure 4.9: Digital Multimeter

Features :

6½ Digit Display (1,199,999 counts)

12 Different Measurement Capabilities ; DCV / ACV, DCI / ACI, Ω2W / Ω4W,

Frequency / Period, Diode Test, Continuty, dB /dBm

High brightness vacuum fluorescent display

True-rms AC voltage and current measurement, bandwidth up to 300kHz

DCV measurement accuracy up to 0.0035%, resolution up to 0.1μV

Max. measurement rate : 1000 meas / sec

Equal accuracy frequency measurement up to 1.1 MHz

Relative mode (REL) to eliminate residual reading

2W, 4W resistance measurement mode selectable

Built-in mX +b, %, dB, dBm etc mathematics calculation function

512 reading storage and MAX / MIN / AVER / STD statistics



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Up to 30,000 readings storage (without statistics)

HI / IN / LO comparator function

USB, BPIB and RS-232 Interfaces provide easy system communication

Calibration without opening the case

10 sets of multimeter setup can be stored and loaded

SPECIFICATION

Operating Temperature & Humidity 0°C - 40°C,≤ 90% RH

Power Requirements Voltage 110V/220V AC ± 15%

Frequency 50Hz/60Hz ± 5%

Power Consumption ≤ 20VA max.

Dimensions 225 x 100 x 355mm (approx.)

Weight 2.5kg (approx.)

Testing for Continuity

This test should be done when current is NOT present. Always unplug the

device or turn off the main circuit breaker before attempting a continuity test. Acontinuity test is done to determine whether a circuit is open or closed

Set the multimeter to the ohm setting. The symbol for ohm is , the Greek

letter omega. If there is more than one ohm setting, choose X1. Note that while the

probes are not touching anything, the multimeter will indicate a reading of infinity. A

reading of infinity indicates that the circuit is open and cannot conduct current. When

you touch the two probes together, the reading changes to zero. A reading of zero

indicates that the circuit is closed and can conduct current. Touch each probe to one of

the terminals (or poles) of the device. If the reading changes to zero the device has

continuity.

To test a switch, place a probe on each pole of the switch. When you move the

switch from the off to the on position, the meter reading should change from infinity to

zero, which implies that the switch is working. To test a component such as a motor,

touch a probe to each pole. A reading of zero indicates that motor has continuity and



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current can pass through it. Continuity test can also be used to test light bulbs. If the

light bulb is burnt, it fails continuity test.

Testing for GroundThis test should be done when current is NOT present. Always unplug the

device or turn off the main circuit breaker before attempting a ground fault test.A

ground fault test is done to determine if current is passing from a circuit inappropriately.

A ground fault is a potentially dangerous electrical shock hazard. A ground fault can

also cause a device to malfunction.

Set the multimeter to the ohm setting. If there is more than one ohm setting,

choose X1. Touch one probe to a terminal and touch the other probe to the device's

housing or mounting bracket. Now move the first probe to another terminal. If the

multimeter displays anything other than a reading of infinity for any of the test

combinations, a ground fault exists and the device should be repaired or replaced. Do

not use a component that has a ground fault.

Measuring Resistance

This test should be done when current is NOT present. Always unplug the

device or turn off the main circuit breaker before attempting to measure

resistance.Resistance is how much the flow of current in a circuit is impeded.

Resistance is necessary for heat to be generated in heating elements like those used in

an electric stove or oven, dryer or hair dryer. It is necessary to know what the proper

resistance rating should be for a particular device in order to determine if it is

functioning properly.

4.2.4 RS-232 COMMUNICTION PORT

What is RS-232?

RS-232 is interface for carry information between two devices distance of up to

20 meters. The information is carry along patch wires higher voltage than is standard

5V for greater interference immunity. Data transfer is asynchronous with closely set

transmission speed and synchronization by trailing edge start pulse.



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In telecommunications, RS-232 is the traditional name for a series of standards

for serial binary single-ended data and control signals connecting between a DTE (Data

Terminal Equipment) and a DCE (Data Circuit-terminating Equipment).

It is commonly used in computer serial ports. The standard defines the

electrical characteristics and timing of signals, the meaning of signals, and the physical

size and pin out of connectors

Figure 4.10: RS-232

Main purpose of RS-232

The RS-232-C interface was developed for a single purpose, unambiguously

stated by its title: "Interface Between Data Terminal Equipment and Data

Communications Equipment Employing Serial Binary Data Interchange." Every

word in the title is significant: it describes the interface between a terminal (DTE) to a

modem (DCE) for the transfer of serial data.

http://en.wikipedia.org/wiki/Telecommunications


http://en.wikipedia.org/wiki/Serial_communication



http://en.wikipedia.org/wiki/Single-ended_signaling

http://en.wikipedia.org/wiki/Data_transmission



http://en.wikipedia.org/wiki/Signaling_%28telecommunications%29



http://en.wikipedia.org/wiki/Data_Terminal_Equipment


http://en.wikipedia.org/wiki/Data_circuit-terminating_equipment

http://en.wikipedia.org/wiki/Computer


http://en.wikipedia.org/wiki/Serial_port




http://en.wikipedia.org/wiki/Data_circuit-terminating_equipment





http://en.wikipedia.org/wiki/Single-ended_signaling





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Figure 4.11: Example of RS232

Connectors

The devices for serial link have been connect by cable with 9-pins or 25-pins

connector type D. You can find many terminology, for example DB-9, DB-9,

CANNON 9, CANNON 25, etc. The connectors are made in male and female type.

Each pin is named and labeled.

Standard

The Electronics Industry Association (EIA) has developed standards for data

communication. EIA standards where originally marked with the prefix "RS". "RS"

means that it is a recommended standard, but the standards are now generally indicated

as"EIAstandards.RS-232 was introduced in 1962. The standard evolved over the years

and had the third revision in 1969 (RS-232C). The fourth revision was in 1987 (RS-

232D also known as EIA-232D) .

WORKING OF RS232 STANDARD

Voltage levels

RS-232 using two voltage levels. Logical 1 and 0. Logical 1 is sometimes

calling as marking estate or quiescent state too, logical 0 is calling as space estate.

Logical 1 is indicate negative level, while logical 0 is indicate positive level. Allow

voltage levels are state in table.



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The Noise Margin Issue

Signals traveling along the cable are attenuated and distorted as they pass.

Attenuation increases as the length of the cable increases. This effect is largely due tothe electrical capacitance of the cable. The maximum load capacitance is specified as

2500pf (picofarad) by the standard. The capacitance of one meter of cable is typically

around 130pf, thus the maximum cable length is limited to around 17 meters.

Problem with power supply

If you connected two computers via RS-232 and each of then is power

supplayed from another power point. We recommended mere voltage between their

signal ground before connection.

Figure 4.12: Working of RS232

The below figure shows the Data siganal and control signals of RS232

Data signals

Level Transmitter Receiver

Logical 0 +5 V to +15 V +3 V to +25 V

Logical 1 -5 V to -15 V -3 V to -25 V

Undefine -3 V to +3 V



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Control signals

Signals Driver Terminator

"Off" -5 V to -15 V -3 V to -25 V

"On" 5 V to 15 V 3 V to 25 V

Table 4.1:Data & Contorl Signals

Pinout

Figure 4.13: Various pinouts of rs232

Wiring length

The length of the cable also plays a part in maximum speed. The longer the

cable, the greater the cable's capacitance and the slower the speed at which you can

obtain accurate results. A large capacitance means voltage changes on one signal wire

may be transmitted to an adjacent signal wire. Fifty feet is commonly quoted as the

maximum distance, but this is not specified in the standard. We generally recommend a

maximum distance of 50 metres, but this depends on the type of hardware you are

connecting and characteristics of the cable.

What is Baud?

The speed of RS-232 communications is expressed in Baud. The unit is named

after Jean Maurice-Emile Baudot (1845-1903), a French telegraph engineer and the

inventor of the first teleprinter. It was proposed at the International Telegraph

Conference of 1927. The maximum speed, according to the standard, is 20000 Baud.

However, modern equipment can operate much faster than this. No matter how fast (or

slow) your connection - the maximum number of readings per second you can take from

your instrument depends on the software.



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Parity in RS-232 communication

Parity is the state of being either odd or even. In serial communications parity

may be used to check for errors in the transmission of data. When performing a parity

check, the instrument or PC sending messages counts the number of 1's in a group of

data bits. Depending on the result, the value of another bit - the Parity Bit - is set. The

device receiving the data also counts the 1's and checks whether the Parity Bit is as it

should be.

Types of parity

To perform a parity check the computer and the instrument must obviously

agree on how they are calculating the Parity Bit. Are they setting it on for an even or

odd number of 1‟s? When a device uses Even Parity, the data bits and the parity bit will

always contain an even number of 1's. The reverse is true for Odd Parity.

Mark and Space parity

Two other parity options often available in driver software are Mark and Space.

These aren't effective in error checking. Mark means the device always sets the Parity

Bit to 1 and Space always to 0.

Detect all errors?

Parity is a rudimentary error checking mechanism. It can detect an error in

transmitting 1 bit, but if 2 bits happened to be wrong it would not pick this up.

It also provides no help as to which bit is wrong. Other error checking mechanisms

include the Start and Stop Bits described below, and cyclic redundancy checks which

are often used in Modbus communications.

ExampleIn the example below you can see how the data frame is composed of and synchronised

with the clock signal. This example uses an 8 bit word with even parity and 1 stop bit

also refered to as an 8E1 setting. The data line consists of a start bit followed by a 8-bit

data word and then by a parity bit and a stop bit .



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Figure 4.14: Dataflow in rs232 standard

Start bit

The data line has two states - on and off. An idle line is always on. When the

instrument or computer wants to send data it sets the line to off - this is the Start Bit.

The bits immediately after the start bit are therefore the data bits.

Stop bit

The Stop Bit is present to allow the instrument and computer to re-synchronise

should anything go wrong: noise on the line masking the start bit for example. The

period of time between the start and stop bit is constant, according to the baud rate and

number of data and parity bits. The stop bit is always on. If the receiver detects an off

value when the stop bit should be present, it knows there has been an error.

Setting of Stop bit

The stop bit is not actually 1 bit but a minimum length of time the line must be

on at the end of each data transmission. On PCs this is normally equal to 1 or 2 bits, and

you must specify this in the driver software. Although 1 stop bit is most common,

selecting 2 will at worst slow the message down slightly.

(You might see an option to set the stop bit to 1.5. This is only used when the

number of Data Bits is less than 7. If this is the case then ASCII characters cannot be

transmitted and so 1.5 is rarely used.)



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4.2.5 TEST COMPUTER

Figure 4.15: A Test Computer

A test computer is system having a CPU(Central Processing Unit)

,Monitor,Keyboard and Mouse .The monitor is used for the display, keyboard and

mouse is used to provide the inputs and give commands .The cpu has all the interfacing

connections connected to it.The input is given to the system having the required

software installed in it.Ths software takes the input from the user like from which pin to

which the connectivity checking has to be performed and this input is passed to the

microcontroller from the cpu with the use of the rs232 intrface and connectors and the

generated ouput is displayed in the monitor and is saved for future analysis.



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Chapter – 5

PROJECT EXPLANATION

In this chapter the working principle of the system “automated harness tester “

and input and output to the system are explained.

5.1 WORKING PRINCIPLE

The main working principle involved in this system is the automatic switching

of the relays and hence it is called automated harness tester since the whole

connectivity testing is performed automatically. This system makes the users very

convenient to operate because with a single click the whole operation is performed

automatically.

Initially the input is given to the test computer according to the user

requirement from which pin to which pin he wants to test the connectivity.The test

computer is externally connected to the 8051 microcontroller through an interfacing

device called RS232 Transreceiver.This device gets the input signal given by the user

from the test computer and sends it to the microcontroller section.

The microcontroller is programmed such that it reads the input given and

performs the necessary action .The ports of microcontroller are connected to the

CPLD.The output of the microcontroller is passed to the cpld which is internally

connected to the control bus.All the inductors of relays are directly connected to the

control bus.The different types of chassis mounts are connected to the relays and each

pin of a chassis mount is connected to two relays to perform the required operation. Inthis project we have used 256 relays for maximum conncectivity of 128 pins.

Suppose if the relays are to switched on then the microcontroller sends a logic

high voltage to the control bus and if it is to be switched off then it sends a logic low

voltage to the control bus.The other terminal of the relay is attached to the multimeter

pins. First relay of each pin is connected to the positive terminal of the multimeter and

second realys of each pins are connected to negative terminal of the multimeter

automatically by the switching action of the relays.



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The multimeter performs the required connectivity test as per the instructions

given by the microcontroller.For example if we want to test the connectivity test for the

pins 1 and 5 then the microcontroller sends a logic high voltage to the pins 1 and 5 and

accordingly they are switched on and as the first relay of pin 1 is connected to the

positive terminal of the multimeter and the second relay of the pin 5 is connected to the

negative terminal of the multimeter and hence the connectivity test is performed by the

multimeter and generates the output.The obtained output from the multimeter is passed

to the test computer through an rs232 communication port and the test computer stores

the result in text format for future use.

Suppose if you want to test the conncectivity of the pins 5 and 1 then usual the

microntroller sends the logic high voltages to the pins 5 and 1 and here the first relay of

pin 5 is conncected to the positive terminal of the multimeter and second relay of pin 1

is conncected to the negative terminal of the mulitmeter and so the connectivity test is

performed for the pin 5 and 1 and the corresponding result is sent to the test computer.

Similarly if we want to test the connectivity for the pins 1 to 55 .First the

multimeter checks the connectivity from 1st

pin to 55th

pin( like for pin 1 and pin 2,pin 1

and pin 3 ,pin 1 and pin 4,……………pin 1 and pin 55) and then it performs the test for

the 2nd

pin to the remaining pins(pin 2 and pin 1,pin 2 and pin 3 ,pin 2 and pin 4…..pin

2 and pin 55).In the similar way mentioned above it performs the test for the remaining

pins.

5.2 INPUT TO THE TEST COMPUTER

The test computer is having the software called Microsoft Visual 2005 installed

in it,which accepts the input given by the user and sends it to the controlling block.The

software is quite simple to use as it has a menu driven screen which has to be opearated

by just one button.



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Figure 5.1 : Input to the test computer

When we open the software in the system a window appears on the screen

which has to be filled by the user according to the requirement.The user need to fill the

below four requirements like the unit no and have to select the connector type ,then he

must mention the initial and final pins that is from which pin to which pin he wants the

test to be performed.After that the software will automatically generate a file name

according to the given data to save the result.The result gets saved in the .txt

format.Finally the user has to press the RUN button on the screen to start the testing

process and have to wait for sometime till the whole operation is perfomed and is

displayed in the window and he must click the save button to store the data in generated

file.

5.3 OUT PUT OF THE SYSTEM

After the completion of the whole process the system will generate the ouput

and display it on the monitor .This ouputs shows the overall connectivity of all the pins

and tells whether the pins are isolated ,continued or short and it also shows the

resistance between the pins of the conncectors.The figure below shows the ouput

generated by the system.



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Figure 5.2 : Ouptut of the system

Here in this project we have performed the test for the pin 1 to 55 and below is

the sample of the ouput generated after the completion of the process.

The below table shows the connection of one pin to the remaining pins of the connector.

PIN No PIN No RESISTANCE

PIN No--1 to other PINS

1 2 +1.91436620E+06

1 3 +1.92375620E+06

1 4 +1.92522470E+06

1 5 +1.92574180E+06

1 6 +1.92611410E+06

1 7 +1.92667250E+06



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1 8 +1.92712750E+06

1 9 +1.92747910E+06

1 10 +1.92822370E+06

1 11 +1.92855460E+06

1 12 +1.93045750E+06

1 13 +1.93051950E+06

1 14 +1.93060220E+06

1 15 +1.93136750E+06

1 16 +1.93111930E+06

1 17 +1.93142960E+06

1 18 +1.93149160E+06

1 21 +8.73735330E+06

1 22 OPEN +9.90000000E+37

1 23 OPEN +9.90000000E+37

1 24 OPEN +9.90000000E+37

1 25 OPEN +9.90000000E+37

PIN No--2 to other PINS

2 3 +1.91535900E+06

2 4 +1.92427330E+06

2 5 +1.92545220E+06

2 6 +1.92584520E+06

2 7 +1.92630020E+06



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2 8 +1.92652770E+06

2 9 +1.92739640E+06

2 10 +1.92805830E+06

2 11 +1.92874080E+06

2 12 +1.93047810E+06

2 13 +1.93051950E+06

2 14 +1.93043680E+06

2 15 +1.93101590E+06

2 16 +1.93126410E+06

2 17 +1.93149160E+06

2 18 +1.93163640E+06

2 21 OPEN +9.90000000E+37

2 22 OPEN +9.90000000E+37

2 23 OPEN +9.90000000E+37

2 24 OPEN +9.90000000E+37

2 25 OPEN +9.90000000E+37

Table 5.1:Connectivity of pins in a conncector



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Chapter – 6

FUTURE SCOPE

This system has the great scope in future because of its fastness and easy to use

sevice. These systems are compulsory required for fault debugging and physical

checking of connectors before they are used. This saves a lot of valuable time and waste

expenses made by the industries. These devices are mainly used in aviation, medical

and industrial market. These systems have the great demand in those markets.

As these testers are fast, accurate and easy to use these systems are very much

preferred when compared to that of the old manual techniques because it completes the

whole process within minutes which is of great help to the companies.These systems

start testing immediately with menu-driven operator screens and it saves the result in

„.txt‟ format and generates reports automatically. Automated Harness Testers are used

in military ,navy,defence and aerospace having electronic sub-systems to find the

defective or miswired cables instantly before they damage equipment or waste valuable

technician time.

Each and every electronics manufacturing industries need to be checked for

their newly designed or manufactured equipment to prevent the equipments from

damaging and so here the automated harness testers are of great use to them. The

results of these systems are of help the industries to modify or correct their designed

equipments before they use.So this system is not only a important for the electronic

industries but also very much compulsory required to get the good products out of their

industries.



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REFERNCES

BIBLOGRAPHY

I. Wikipedia – The free encyclopedia

II. http://www.8051projects.info/

III. http://instructables.com

IV. /www.dynalabtester.com/

V. www.camiresearch.com/

VI. www.ditm.com/-United States

VII. http://www.alldatasheet.com/

VIII. http://www.datasheet4u.com/

IX. http://www.datasheetcatalog.com/

http://instructables.com/

http://instructables.com/



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APPENDICES

SNAPSHOTS:

An overview of the project

The backside of the kit



40

The front part of the kit

Figure showing the connection of rs232 to the kit



41

Figure showing a J108 conncector

Figure showing the rs232 conncected to multimeter



Figure shows the J108 connector to the kit

Figure above shows the rs232 conncected to test computer and multimeter

Documents

A project on automated harness tester