How to Make a Copper Oxide Diode

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Introduction: How to Make a Copper Oxide Diode

A diode is an electrical device that allows power to travel in only one direction.
Diodes can be made of Silicon, Germanium or even copper oxide.
Note: The there is only one alligator clip connected to that wire, the other is an illusion.

Step 1: Aquiring Copper

I used some copper wire 6 inches (14CM), use any fair size (22AWG or larger) copper wire with all insulation striped off.
Wash it in clean (preferably distilled) water.

Step 2: Making Copper Oxide

You will need alot of heat ;)
The best solution is to put it in a propane torch glowing red for a minute or two.
Hold it with pliers!
You may be able to use another heat source but the copper needs to turn red.

Step 3: Making the Diode

Carefully clip an alligator clip to one end and loosly wrap a piece of wire around the other end.
Avoid damaging the black/red oxide layer.

Step 4: TEST!

I used two AA batteries and a digital meter:


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    6 Comments

    Has anyone tried using one of these for a crystal radio?  It is akin to the old foxhole radios with the oxide on the razor blade preforming this function.

    Many years ago I had a turntable that due to poor contact acting as a diode, captured an AM radio station. At times you could hear perfectly, like a radio instead of a turntable.

    In step 4 you are showing that the current flow through the diode in one direction is different than in the other direction.  Is that correct?

    1 reply

    Yes, Notice the - sign, you will see quite a bit more volts foreward vs backwards.

    Once the copper is red hot you can stick it  quickly in some water. The red oxide will form very quickly but there is the danger of steam. I found this out with I smelted copper with a arc furnace and then kicked the blob in water. The grey outer coating quickly turned a nice red color. I still have the blob too.


    1 reply