Continuity Tester

Continuity Tester Schematic

A continuity tester is a pretty simple beast.

Take an LED and connect it to a battery with a big enough resistor to keep it from frying.

Congratulations, you've made a light.

Next, snip a wire between the LED and the battery. Attach some wires.
Now, you've got a light that only lights up when the wires touch or are connected by something with really low resistance. That's a continuity tester.

So why do you care? Say you're making a thingie to connect an SNES gamepad to your PC... It's handy to be able to tell what wire at one end of a cable is connected to what plug on the other end.

Stuff we'll need:

  • An LED
  • A battery connector and a battery
  • A resistor (use an LED calculator to figure out how big)
  • A box to put it in
  • some wire to use as probes
  • (opt) some aligator clips or pointy nails to use as ends of the probes



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Hey Ripley, don't worry. Me and my squad of ultimate badasses will protect you! Check it out! Independently targeting particle beam phalanx. Whoa! Fry half a city with this puppy. We got tactical smart missiles, phase-plasma pulse rifles, RPGs, we got sonic electronic ball breakers! We got nukes, we got knives, sharp sticks...

Hudson