Introduction: How to Make a Copper Oxide Diode

Picture of 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

Picture of 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!

Picture of TEST!

I used two AA batteries and a digital meter:


stone3408 (author)2010-05-11

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.

rimar2000 (author)2010-05-09

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.

Phil B (author)2010-05-09

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?

smeezekitty (author)Phil B2010-05-09

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

Nerdz (author)2010-05-08

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.

smeezekitty (author)Nerdz2010-05-08

Thanks for the tip!

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