How to make a logic probe

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Logic probes are wee little things that show the state of a logic pin.
Peats and maplin sell them for some obscene amount of money (about 20 euro) - its easy to make one for about 10 cent.

Ingredients:
Bits of wire (gratis)
One led (gratis)
Some form of clip, or probe (couple of cent)
Someone to 'lend' you a biro

Instructions:
  1. Chop off the back end of the biro
  2. Push the nib and ink tube out from the back. Then seperate them
  3. Put a hole in the biro tube just big enough for the led.
  4. Solder two long-ish pieces of wire unto the led.
  5. Push it all into the hole drilled in the biro, with the wires goign to seperate ends. Observe polarity! Glue the led for sturdiness.
  6. Solder one wire to the end of the biro, and stick it back where it came from. May as well glue it - everything is already very messy.
  7. Solder the other wire to the probe. Glue the wire at the exit point from the tube so it doesnt get pulled on.

Note: You can break the led by say, connecting the nib to 9 volts, or something that results in a large current. If youre paranoid, put a resistor somewhere convenient.
Logic probe