Wireless LAN cable tester

[Kamikaze47]

Thanks for the suggestions. I don't really want to use mains for ground - mainly because it will make the device much more bulky with a power cord and also less convenient because it would need a power outlet near by.

I'm sure there must be some ingenuous technique that the commercial LAN testers use.

[cncmachineguy]

I don't know much about them, but how about making one end a "one wire" device. then the smart end could send a OWOUT on each pin.

Or even easier, how about just a loop back plug for 1 end. then you could send a signal out each of four wires and expect it back on the coorsponding wire.

[mark_s]

Looks like they use RF.

http://www.google.com/patents/about?...axy_is=&num=10

[Kamikaze47]

I don't know much about them, but how about making one end a "one wire" device. then the smart end could send a OWOUT on each pin.

Or even easier, how about just a loop back plug for 1 end. then you could send a signal out each of four wires and expect it back on the coorsponding wire.

Unfortunately, 1-Wire still needs a common ground.

The loop back plug is a good idea. The only thing I can think of that it wouldn't be able to test is if there happens to be a short across one of the pairs. I don't that's going to happen very often however. If I cant think of anything better, I think I'll probably use that method.

[cncmachineguy]

Maybe the loopback plug could employ some sort of passive delay, so you could measure the time between sending a signal and getting it back. That way if there is a short you will see it as instant response.

[dhouston]

The loop back plug is a good idea. The only thing I can think of that it wouldn't be able to test is if there happens to be a short across one of the pairs.

Why not? Four reed relays and a PIC in the remote device would allow you to either short or open the pairs.

This URL gives you a better method of checking for a shorted pair...http://www.epanorama.net/circuits/tdr.html