LAN cable tester using pic16f876

I am in the process of designing a system to test short circuits and open circuits on cat5 UTP LAN cables. I want now to be able to determine where the fault is exactly relative to point of testing.

How best can I do it

Please help

traditionally this would be done by using time domain reflectometery...
so maybe it's a TDR meter and a scope you need...rather than just a simple go/no go type tester

I don't think it is really necessary to pinpoint the location of a fault in cat5 cable as the maximum length of a section is normally limited to 100m and making any repairs to it would degrade performance.

Surly it is easier to just test end to end, if faulty change the rj45 plugs (the most likely source of a fault) and if still faulty, change the cable (which is not that expensive anyway).

Thanks picsam for the contribution, but I just wanted to find out how one would do it using a pic. I will take your advice.

normally limited to 100M ?

hehe...last few I have seen were more like 500m trailing through a building...
anyway...it's nice to be able to test that 1000M reelpac ya just bought off ebay....

I use a Cat5 cable tester similar in concept, a dual LED strips show whether the cable is connected correctly. That one cost $30 and seems to consist of a 4017 and a 555 as the only two ICs on board, the LED module may have some help built in. Its compact, works very well and really fast unlike the Wirescope 350 I would otherwise have to use to do the same job. I haven't bothered to work out the circuitry as I know I couldn't build one any cheaper.