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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Mandy, you have to believe me! The clowns want to take over and become the dominant species! They will Destroy us all! Destroy us all! Destroy us all! Destroy us all! Destroy us all! Destroy us all!

Billy