DIY Cable Testers for Electronics Projects

Written by michael carroll
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DIY Cable Testers for Electronics Projects
A simple cable tester quickly indicates the integrity of cables with lights. (cable image by Eldin Muratovic from

Cables are among the most vulnerable pieces of electronic equipment, as they are often subjected to mechanical stress. In many electronics projects it is important to verify the integrity of cables frequently, as they endure more wear and tear than normal when swapped and moved around during testing. You can make a simple cable continuity tester to verify the integrity of cables over time, and to test new cables if you are making your own.

Skill level:

Things you need

  • 2 cable connectors
  • Small box
  • 9-volt battery
  • 1 resistor per wire in cable, 400 Ohm
  • 1 LED per wire in cable

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  1. 1

    Mount the cable connectors on the top or sides of the box so that you can quickly plug both ends of a cable into the connectors.

  2. 2

    Connect the positive terminal of the battery to one leg of each resistor, then the other legs of the resistors to the positive legs of the LEDs (the positive leg of an LED is the longer of the two). Connect the negative terminals of the LEDs to the pins on one of the connectors.

  3. 3

    Connect the pins of the second connector to the negative terminal of the battery. Now, when a working cable is plugged into the two connectors, each LED will be connected through the cable to the negative terminal of the battery and will light up. If one of the wires in the cable is broken, its LED will not light or will flicker, indicating that the cable has failed.

Tips and warnings

  • Strictly speaking, this type of tester can be "fooled" by a cable whose internal wires have somehow become connected to each other; this condition is unlikely, and in almost all typical situations will result in flickering, inconsistent lights.

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