Many circuit harness tester design / build

Thread Starter

tomcat_meow

Joined Jan 5, 2012
12
I am involved in a wire harness manufacturing business that builds very large wire harnesses with many circuits that are usually branching out over a large area like a 4ft. by 8ft. or even larger build board. Usually we just buy a circuit tester which is very expensive and overkill for what we need which is just to see that a wire circuit is properly housed in a connector and placed and run through the harness to it's other end where it should go. We only need to verify the circuit. The bought harness testers are slick but at 10 k it becomes a financial burden especially when we need many of them for all sorts of harnesses as we expand the business. So I thought it would be worth the look to see if there is advantage to building a DIY system . The bought system can learn a known good harness and store it in memory (called up when you need it again) once it is put on the harness test/build board. Presently I build an interface from the board to the tester which involves running wires from mating connectors to the tester and placing the mating connectors on the front side of the board so the build person can plug in the various parts of the harness and build a complete harness. The bought system also monitors the build in real time so that if a mistake is made it beeps to alert the build person. The bought tester has a standard 256 connections and then you have to buy add on sections each time for another 256 at 1500 for each 256 test points. I need at least 512 and sometimes more. So what I'm looking for suggestions from some knowledgeable folk on which way to approach design of this tester. I'd like to use an arduino if possible to housekeep counting and logic. Not sure but some sort of multiplexing system or if there is some sort of cascadeable addressable logic switch out there that I don't know about or some other LSI that would help. I've attached a simple drawing(paint) to explain the basic idea. testeridea.png
 

mvas

Joined Jun 19, 2017
537
What about NI LabVIEW ?
Use an internal PCI Digital I/O Card with a desktop or a USB Digital I/O Module with a laptop.

I would use a Multiplexer on both the Output Pins and the Input Pins.
Much like a keyboard scanner, looking for a "key press".
 
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CharlesWMcDonald

Joined May 16, 2019
233
You need industrial I/O so it will be robust, you couldn't just connect to a logic device because static electricity or other voltage transient would damage the I/O point. Is each point bidirectional or do you have dedicated inputs and outputs?

If you build your own you probably wouldn't save anything on the I/O devices but should be able to get substantial savings on the test controller. Part of this depends on how fast you need to test the points and if you have to do it sequentially or if some points can be tested in parallel. If you are worried about a short between any one wire and any other wire you will need to do it sequentially.
 
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MaxHeadRoom

Joined Jul 18, 2013
20,425
You need industrial I/O so it will be robust, you couldn't just connect to a logic device because static electricity or other voltage transient would damage the I/O point. Is each point bidirectional or do you have dedicated inputs and outputs?
If you build your own you probably wouldn't save anything on the I/O devices but should be able to get substantial savings on the test controller.
PLC is industrial strength, although there are quite a number of I/O required .
The other option is to use a micro based system and use Opto22 industrial I/O boards for industrial strength interface.
Max.
 

be80be

Joined Jul 5, 2008
2,023
Hell what you all talking about they use a plan old arduino mega in car washes for making sure your 2000 dollar car don't hit that 70,000 dollar truck in front of you.
And the little box is about 2000 no install instructions
It replaced a pic with a seven segment
To a meg with some kind of cell phone screen.
 

Thread Starter

tomcat_meow

Joined Jan 5, 2012
12
You need industrial I/O so it will be robust, you couldn't just connect to a logic device because static electricity or other voltage transient would damage the I/O point. Is each point bidirectional or do you have dedicated inputs and outputs?

If you build your own you probably wouldn't save anything on the I/O devices but should be able to get substantial savings on the test controller. Part of this depends on how fast you need to test the points and if you have to do it sequentially or if some points can be tested in parallel. If you are worried about a short between any one wire and any other wire you will need to do it sequentially.
It would need to be sequential then. That is how the expensive testers work.
 

CharlesWMcDonald

Joined May 16, 2019
233
So the next question is; how deep do you want to go? Are you looking for existing digital I/O modules or do you intend to design the I/O yourself?

You also need to make sure there are no patents that would prevent you from creating your own solution.
 

mvas

Joined Jun 19, 2017
537
I have used OPTO-22 Digital I/O Racks for my Cable Tester
An empty 24-bit I/O rack ...
https://www.opto22.com/products/pb24
The 50 Pin Cable connects the I/O Rack to the Digital I/O Card.
Built-In LED Status lights make debugging much easier.

My Cable Tester had a "Learn" mode ...
a) Connect a known good cable
b) The software will scan & learn all of the inter-connections
c) Save the digital pattern to a SQL database with Cable ID (UPC)

When a new cable was completed, we plugged it in to the Test Jig and tested it offline.
We could not test in Real Time.

All tests were saved to a SQL Database with ...
a) Status = Pass or Fail, with the failed Open Pins or Shorted Pins
b) Date & Time
c) Cable ID
Test History is a good thing


http://documents.opto22.com/0727_G4_Digital_IO_Data_Book.pdf
 
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Thread Starter

tomcat_meow

Joined Jan 5, 2012
12
I have used OPTO-22 Digital I/O Racks for my Cable Tester
An empty 24-bit I/O rack ...
https://www.opto22.com/products/pb24
The 50 Pin Cable connects the I/O Rack to the Digital I/O Card.
Built-In LED Status lights make debugging much easier.

My Cable Tester had a "Learn" mode ...
a) Connect a known good cable
b) The software will scan & learn all of the inter-connections
c) Save the digital pattern to a SQL database with Cable ID (UPC)

When a new cable was completed, we plugged it in to the Test Jig and tested it offline.
We could not test in Real Time.

All tests were saved to a SQL Database with ...
a) Status = Pass or Fail, with the failed Open Pins or Shorted Pins
b) Date & Time
c) Cable ID
Test History is a good thing
I have used OPTO-22 Digital I/O Racks for my Cable Tester
An empty 24-bit I/O rack ...
https://www.opto22.com/products/pb24
The 50 Pin Cable connects the I/O Rack to the Digital I/O Card.
Built-In LED Status lights make debugging much easier.

My Cable Tester had a "Learn" mode ...
a) Connect a known good cable
b) The software will scan & learn all of the inter-connections
c) Save the digital pattern to a SQL database with Cable ID (UPC)

When a new cable was completed, we plugged it in to the Test Jig and tested it offline.
We could not test in Real Time.

All tests were saved to a SQL Database with ...
a) Status = Pass or Fail, with the failed Open Pins or Shorted Pins
b) Date & Time
c) Cable ID
Test History is a good thing
 

Thread Starter

tomcat_meow

Joined Jan 5, 2012
12
I have looked at the opto-22 system , I haven't priced then out yet but looks like I would need a boat load of racking for 1024 test points which is where I'm heading because this will basically provide enough capacity to test 512 individual circuits . The largest harness we manufacture has 390 circuits needing 2x that for connections now so this will give us a little head room. I have found a possible solution with a company called land boards which has an I2C multiplexing bus which can take 4 of there digio32 I/O boards . This provides as follows.

32 bits per DIGIO32 card
4 DIGIO32 cards per I2C bus
8 I2C busses per CPU
= 1024 connections 512 for row A and 512 for row B

I will likely use a raspberry pi and store data in an sd card
 

Thread Starter

tomcat_meow

Joined Jan 5, 2012
12
If static electricity becomes and issue we would statically ground the operator and jig but the testers we use now take direct connections from the test jig to TTL I/O so I don't think there is an issue with static .
 

Thread Starter

tomcat_meow

Joined Jan 5, 2012
12
I prefer to find modular I/O that I can interface with a cpu. I may have found a possible solution from a company called Land Boards LLC but open to other suggestions if you have one.
 

tindel

Joined Sep 16, 2012
715
This probably goes without saying, but I'm just throwing this out there in case you've looked over it - have you considered making cables to test your cables? The idea is that you only buy one professional tester, and use it for every single cable you make. You then make cables that mate to the cable under test. It takes some time to make all the cables you need, but it pays off eventually. Then you only have to buy one tester - or a few for different locations, departments, etc.

My opinions: Testing cables is more than just testing continuity! You also must test isolation to verify build quality. I can't tell you the number of times I tested a cable that rung out well continuity-wise, but failed hi-pot. All sorts of reasons - nicks in the wire, pins not seated properly, wire not crimped to pins properly, backshells weakening insulation, etc. My opinion is that it only takes a few of these to see the value in the quality control from both hi-pot testing and the high price of the tester.

My first job out of college, I designed a cable tester for a big aerospace application - I'm told it's still used today - believe it or not - over a decade later. I used the Cirrus CH2's, for what it's worth. I put the CH2's in a rack, with a computer and monitor, and made a panel that had panel mount ZIF's that interfaced with the CH2's internally. Externally I designed and built about 100 (only a slight exaggeration) test cables that interfaced to the flight cable connectors and rear panel ZIF's. It was a massive project (took me over a year to complete), and the setup took a couple days, but in about 5 minutes the entire spacecraft harnessing build quality was verified and validated, with test data to go along.

This is probably almost certainly overkill for your application, but my point is that it is worth the quality for your customer to use quality equipment that probably has years worth of design heritage. I'd encourage you to look for other ways to reduce costs or increase revenue. Some ideas (low hanging fruit, probably): Look at using another tester supplier, start providing test data to your customer to show additional value (potentially getting more work), find ways to build and test cables more efficiently think "Lean".

Good luck!
 
There is an IC called a PIN Driver. See https://www.analog.com/media/en/technical-documentation/data-sheets/ADATE302-02.pdf for an example. It could probably be used to do comprehensive tests. Right now, I havn't a clue.

FWIW: I don't have an Ethernet cable tester/certifier, but I don't trust the scanning cable testers. I prefer th 4 bicolor LED's for each pair. Why? Because I can flex each end and see a connection dissapear. I can't with a scanner.

I would hope that a certifier would identify the bad crimp.
 
I prefer to find modular I/O that I can interface with a cpu. I may have found a possible solution from a company called Land Boards LLC but open to other suggestions if you have one.
If you up to designing your own solution I recommend using industrial I/O chips. If your quantity is high enough you could get the cost down. Design it yourself and have it contract manufactured.
Maxim has some devices that would work well for this application. I've attached the specifications and an industrial I/O design guide. These chips are digital, not analog. If you need to measure the voltage input you would need a different input device. The chips are intended for application in PLCs so they have the robust characteristics you would need.
 

Attachments

Thread Starter

tomcat_meow

Joined Jan 5, 2012
12
This probably goes without saying, but I'm just throwing this out there in case you've looked over it - have you considered making cables to test your cables? The idea is that you only buy one professional tester, and use it for every single cable you make. You then make cables that mate to the cable under test. It takes some time to make all the cables you need, but it pays off eventually. Then you only have to buy one tester - or a few for different locations, departments, etc.

My opinions: Testing cables is more than just testing continuity! You also must test isolation to verify build quality. I can't tell you the number of times I tested a cable that rung out well continuity-wise, but failed hi-pot. All sorts of reasons - nicks in the wire, pins not seated properly, wire not crimped to pins properly, backshells weakening insulation, etc. My opinion is that it only takes a few of these to see the value in the quality control from both hi-pot testing and the high price of the tester.

My first job out of college, I designed a cable tester for a big aerospace application - I'm told it's still used today - believe it or not - over a decade later. I used the Cirrus CH2's, for what it's worth. I put the CH2's in a rack, with a computer and monitor, and made a panel that had panel mount ZIF's that interfaced with the CH2's internally. Externally I designed and built about 100 (only a slight exaggeration) test cables that interfaced to the flight cable connectors and rear panel ZIF's. It was a massive project (took me over a year to complete), and the setup took a couple days, but in about 5 minutes the entire spacecraft harnessing build quality was verified and validated, with test data to go along.

This is probably almost certainly overkill for your application, but my point is that it is worth the quality for your customer to use quality equipment that probably has years worth of design heritage. I'd encourage you to look for other ways to reduce costs or increase revenue. Some ideas (low hanging fruit, probably): Look at using another tester supplier, start providing test data to your customer to show additional value (potentially getting more work), find ways to build and test cables more efficiently think "Lean".

Good luck!
 

Thread Starter

tomcat_meow

Joined Jan 5, 2012
12
We presently use a 12K expensive cirris tester and move it around from board to board for the large harness boards. We have 4 or 5 that can handle 128 connections and only one that can do the Hipot test that we rarely use . The harness board is sort of a mating harness it is just built onto a board which guarantees specific lengths and branches happen properly. see pics. cirrisconnections.jpg harnesstestboard.jpg All our wires are cut by automatic machines that check for insulation damage as they are processed and all crimp terminals are also crimped automatically with crimp quality monitoring. All housing insertions are QC checked in sub assembly stages . I could see if you are manufacturing a product for aerospace or aircraft but these are harnesses shown in the pics above are for vending machines . We have never had a harness get returned for being wrong or bad, only damaged by our customer on installation or driving over them with a fork truck once happened. We mainly use this cirris tester because of the expansion box to allow for 256 connections. I don't like having to carry around a 10k machine around the factory from board to board, plus we are now needing two boards as production has increased and we need two stations working at the same time. I like the cirris for its operator assistance while building because it continuously scans for errors so if the operator makes a mistake he/she is notified in real time and it stores up to 50 programs that can be called up (we have 3 models built on the same board shown) It also notifies the operator that the build is complete so the tying up process begins and it gets tied up and is still scanned which is kind of like an intermittence test at the same time because the harness is getting pulled on more or less all the way along it and at every breakout.
 
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