With two cheap integrated circuits and a few parts from the ‘junkbox’, this very simple and useful circuit, can be put together in just a few hours.
This cable tester, tests all the 8 wires in a network cable in one move, if one of the 8 LEDs does not lit up, it means that the wire corresponding to that LED is faulty.
- 1 x 4017 decade counter,
- 1 x 555 timer,
- 8 x LEDs,
- 2 x 8P8C modular connector (RJ45),
- 8 x 100Ω resistor,
- 1 x 10KΩ resistor,
- 1 x 15KΩ resistor,
- 1 x 4,7µF capacitor.
The yellow LED has no special significance, I only had 7 green LEDs.