Continuity Test Module

[rameshyrvr]

Hi. I want to design a continuity tester that can test the continuity of wiring. I'm planning to use an analog multiplexer, a pattern generator IC, and a simple 5V voltage source and an Led arrangement for the test. Please suggest any better ways to do it.

The block diagram is attached.
Please check my thinking and suggest.
Thanks in advance for help.

 

[VEBill]

On your diagram, which wire(s) is (are) the wire(s)-under-test?

 

[rameshyrvr]

one end of the wires are connected to the multiplexer ic and the other end is connected to the demultiplexer IC. I'm planning to sequentially test the wires by changing patterns with the help of a pattern generator.

 

[IRstuff]

Is continuity really the only thing you care about? What about shorts?

TTFN
faq731-376

 

[rameshyrvr]

even shorts. To find shorts only I'm intending to do this continuity test.

 

[VEBill]

What's the purpose of the ever changing patterns?

The only thing similar that I've seen before is a massively parallel version where wire-specific data is placed on each wire so that the individual wires can be distinguished and identified at the far end (by a single user). Such systems are complex two-box systems. Your diagram of a single channel does not match that application, leaving me confused of its purpose.

 

[VEBill]

Is this related to the 60 channels of fusible resistors?

 

[IRstuff]

You keep refering to it as "continuity" but a shorts test is shorts test. I don't see the need for pattern generation sin e there is ostensibly no memory or processing involved with your wires.

TTFN
faq731-376

 

[rameshyrvr]

Thank you all for your replies.

I slighty modified the design to suite the requirement. The updated design block diagram is attahed here:[link]http://files.engineering.com/getfile.aspx?folder=d901f15a-e19a-49ee-b564-36d7fe251a5a&file=continuity_tester.png[/url].
I'm intending to have two modules: Control module & plugin module. The control module connected to one end of wires has the demultiplexer, some voltage source and a way to give input to the select lines(sorry in diagram it's Digital output).Also the select lines of the Multiplexer.

The other end of wires is connected to the plugin module which is a mux connected.
Intended Working: voltage will be passed to one wire at a time by using the select lines of the multiplexer. The output at the other end will be verified at all the wires by using the select lines of the demultiplexer. After analyzing the output at the voltage receiver end for all the wires, input will be given to next wire at the demultiplexer side and same process is repeated.
By thorough analysis both the short and continuity of the wires can be tested.

Help me in the implementation of this concept.
Thanks in advance.

 

[IRstuff]

Per your "schematic" you do not require a pattern generator, only a fixed voltage. However, you do need as many resistors to ground as you have wires. You apply a voltage to a single wire on one end, and you check each of the other ends of the wires to determine if one, and only one, wire has the applied voltage. If none, or more than one, do, then you have, respectively, an open, or one or more shorts.

TTFN
faq731-376

 

[IRstuff]

If you wish to get fancy, you can select resistors that might allow you to determine whether you have a partial open, as that would result in a measurable voltage that is less than the applied voltage.

TTFN
faq731-376

 

[rameshyrvr]

Thanks for the reply.
Surely I have that resistor arrangement in my module.
Now the hurdle that I'm facing is selecting an MUX. I have around 500 odd wires to be tested. I'm intending to test around 32/64 at a time. PLease suggest an reliable Mux IC having 64 channels.

 

[IRstuff]

Why can't you do this? Have you tried this wonderful tool called Google?

TTFN
faq731-376

 

[VEBill]

Buy or rent one:

http://www.cirris.com/cable/tester/testers.html

 

[rameshyrvr]

Thanks.