Short Circuit Tracer for a Buck

Almost every meter you find today will have a continuity tester. Connect the probes and it will beep if there is a short and won't if there isn't. But where is the short? That's another problem when trying to measure a component that is connected to many other components. [Learn Electronics Repair] wanted to have a tool to find shorts on a board and wanted to build a tester that uses 4-wire resistance measurement to isolate the device under test without having to do surgery on the circuit. His $1 build appears in the video below.

The first part of the video talks about the theory behind resistance measurement with two and four wires. Let shows several diagrams, but he mentions that at one point he shows an incorrect schematic (at 12:03) instead of the early correct one (at 10:35) and mentions it, but if you are skimming the video, you might get confused.

An old video card with an introduced capacitor short makes a good demo. The meter is able to tell where the short circuit is. The probes won't win a beauty contest, but it looks workable. The measurement is actually the voltage drop induced by a constant current source, so it isn't handy to read the actual resistance, but it will show you where a branch is shorted. You could actually do this essentially for free if you have a constant current bench supply and some extra wires.

We've covered 4-wire measurements before, with a focus on how they can zero out lead resistance, but the same idea applies. If you prefer your explanations in a video, we saw one recently.

#toolhacks #4wireresistance #continuitytester #shortcircuit

Ethernet Tester Needs No LEDs, Only Your Multimeter

Ethernet cable testers are dime a dozen, but none of them are as elegant and multimeter-friendly as this tester from our Hackaday.io regular, [Bharbour]. An Ethernet cable has 8 wires, and the 9 volts of easily available batteries come awfully close to that - which is why the board has a voltage divider! On the 'sender' end, you just plug this board onto the connector, powered by a 9 volt battery. On the "receiver" end, you take your multimeter out and measure the testpoints - TP1 should be at one volt, TP2 at two volts, and so on.

As a result, you can easily check any of the individual wires, as opposed to many testers which only test pair-by-pair. This also helps you detect crossover and miswired cables - while firmly keeping you in the realm of real-life pin numbers! This tester is well thought-out when it comes to being easily reproducible - the PCB files are available in the "Files" section, and since the "receiver" and "sender" PCBs are identical, you only need to do a single "three PCBs" order from OSHPark in order to build your own!

Bharbour has a rich library of projects, and we encourage you to check them out! If you ever want to get yourself up to speed on Ethernet basics, we've talked about its entire history - and we've even explained PoE! After some intensive learning time, perhaps you can try your hand at crimping the shortest Ethernet cable ever.

#networkhacks #toolhacks #cabletester #continuitytester #ethernet #ethernetjack #hackadayio #networktester