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Network cable tester

Posted on Friday, September 15th, 2017 in DIY by DP

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Dilshan Jayakody writes, “This is an automatic Cat6 / Cat5 network cable tester designed using NE555 timer and 4017 decade counters. This unit test all 8 wire lines of twisted pair network cable and indicate pass/fail status with single LED. We design this unit to test network connectivity issues in Cat6 / Cat5 cable systems and it is capable to check both crossover and straight-through type network cables.”

More info on his blog here.

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4 Responses to “Network cable tester”

  1. KH says:

    Oh ahem Dilshan, it will pass all other kinds of wire arrangements too. Slave socket is wired as a 7-input wired-OR logic with white+green as the logic output line. How would it check the correct mapping of wires? It would only sort-of check one-to-one continuity. Not sure about shorts, it will depend on the 4017. So please correct me if I am wrong (and I’ve stared and stared and stared at the schematics) but I don’t see how this scheme can correctly check wiring arrangements.

    (The 555 is wired as an oscillator, ~8Hz. One 4017 is to sequence wire connection tests from 0 to 6, the other 4017 counts successful connections and lights up on 7 successes. The tests are done with the 8 lines of the sockets/cable wired as a 7-input OR logic gate.)

    Better use an MCU with at least 16 I/O lines, enough to eliminate all ambiguities, verify approved wiring combinations, any shorts, plus enough ADC channels to check for slow leaks. And if anyone wants to repair cables, then we would need a useful info display.

    • Erwin says:

      I can’t imagine that anybody will bother to build such a scrap that won’t even detect swapped wires at all. On ebay, you can get network testers for $3 that have a seperate led for each wire.

    • Max says:

      Considering it only seems to test that all wires conduct, I’m not sure what exactly does this show you that 7 LEDs each powered through one of the wires wouldn’t, as soon as you plug them in. Actually, 4 LEDs powered through an appropriate pair-wise loopback on the other end would even also test mapping at a rudimentary level. Inevitably, Rube Goldberg comes to mind…

      • KH says:

        I guess this is a failed attempt at making a pass/fail cable tester out of discrete ICs.

        A single pass/fail LED is not that useful. IMHO we really need something to verify that the wires are in one of the approved wiring combinations (especially for troubleshooting etc.) This kind of project is useful only in say, a very IT-backward country. One site I saw while searching for similar circuits claims that such circuits is useful for cable repair in Africa. But I would just go to a shop I know who does custom cable lengths, they can cut, crimp and test, all done in a couple of minutes.

        It would not be economical for someone in a country with pretty good IT infrastructure to fix an Ethernet cable; I would swap, then dump the bad cable. I once had a USB cable with one wire broken — I cut it up to trace the break, and the end result is of course, an unusable mess. Luckily, it still ended up a bit useful since I saved one end for a PIC18 USB board, ha ha.

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