There are obviously the commercial options. These range from the really low quality units for £5 from eBay up to the seriously exotic Fluke devices which start around £700 and head skywards rapidly. With that in mind I have decided to build my own. My needs are quite basic, to be fair the cheap eBay unit would do. But I reckon I can build something more compact, sturdier, and chocked full of geek-cred. I call it CatsEyes.
The device has two parts, one to be connected at each end of the cable under test. Shown above is the circuit I have built for the 'far' end but I'm currently struggling to layout the 'near' end. There are 9 LEDs which are flashed one at a time to indicate a functioning wire. The 9th (green) LED tests the shielding for continuity on suitably equipped cables.
The LEDs are connected to output pins of the MSP430 on the near-end device. When a single pin is switched high the remaining pins sink the current back from the far-end, through its diodes.
As I wrote, I haven't worked out a nice design for the near-end circuit yet so it's currently a crude jumble of wires on a tiny breadboard patching an 8P8C connector to the LaunchPad. I have a simple version of the code written and tested which just steps through eight outputs, lighting the LEDs on the far-end device. For the time being here's the working code so far:
Leave me a comment if you know of any resources to help me learn about board layout - the circuit above is the first one I have ever built, I hope that fact isn't too obvious! I'll post a video of the device operating in a day or so when I've added a little more functionality to the code.