Capacitor Discharge Pen.

When working with electronics you need to discharge capacitors before yo can troubleshoot a circuit. I’ve seen and done some crazy things to discharge a cap. Like using a screw driver to short out to ground a cap. Works fine but if the voltage is high enough you’ll be asking for it.

So here is a quick, easy and safe way to make a discharge pen for low voltage circuits.

Parts list:
Expo dray erase marker
Primary wire 14 or 16 gauge
Alligator clip or banana socket for bread board use.
Radial 3 watt 1K ohm resistor.

Rip apart the marker by pulling out the felt tip with some pliers. Remove the end cap as well to remove the ink sponge. Clean out the marker tube. A 3watt resistor will fit perfectly where the felt tip was. So solder on the primary wire to the resistor then insert wire first into the marker tube and push firmly to make the resistor sit in place. Drill out the end cap and push the wire thru. You could tie a knot in the wire before inserting the wire into the end cap to act as a strain relief. If you plan to use a banana socket then there is no need. Push in the end cap and add the Alligator clip.
Now depending on how long of a probe tip you want you can cut the resistor lead as short as you wish.

To use the pen you connect the end cap side to ground and use the pen tip to positive.

This can also be used crudely as a load for low power circuits.


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