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New Battery systems => Super capacitors => Topic started by: AbbaRue on November 20, 2005, 10:00:35 PM

Title: Homemade Diodes
Post by: AbbaRue on November 20, 2005, 10:00:35 PM
A homemade diode that can take high voltage and won't burn out. Sound Good?
Place an aluminum electrode and a chromium or stainless steel electrode into baking soda and water.
The aluminum plate is the cathode(+ output ) and the other metal plate is the anode(- output)
I made an awsome bridge rectifier from an old plastic egg carton.
Using the top and bottom parts of the carton to make 4 diodes of 6 chambers each. 
This baby can handle over 1000 volts. and if you short it out there is nothing to burn out.
Not usefull for portible devices but it works awsome for home experimenting.
Just using 4 chambers in a bridge setup, works well up to about 160 volts.
The baking soda mixture is about 1 table spoon in 2 cups of water. This isn't that critical.
The aluminum plates I used were about 1/2 inch wide.
and I used chromium plated metal for the other plate about the same width.
I cut the chromium plates from chromium trays I got at the dollar store, but stainless steel works well to.
In fact almost any metal will work for the anode, but the cathode must be aluminum,
but many metals will make the water dirty, so I recommend chromium or stainless steel.
Hope this will come in handy for someone who needs a diode in a hurry that don't burn out.
This also works as an electrolytic capacitor. [diode and capacitor in one interesting concept]
If anyone comes up with another metal besides aluminum that works let me know please.

Title: Re: Homemade Diodes
Post by: triffid on March 25, 2008, 09:50:38 PM
Titaninum might work too.I made a liquid diode such as you described.baking soda solution using lead and aluminumRan 110 volts household  through  it for a few seconds(about 5).the solution was yellow whereas before it was clear.tiffid
Title: Re: Homemade Diodes
Post by: Koen1 on March 26, 2008, 02:27:21 PM
Seems to me this would produce electrochemical inter- and reactions...
doesn't it?
Perhaps not yet with the materials you're using, and the polarity you're
But everyone knows aluminium oxidises quite rapidly and then forms
aluminium oxide which seriously hinders any electrical current.
Seems to me that would definately have a negative effect on the diode

Nice and simple oldschool tinkering though, I like that. :)

Title: Re: Homemade Diodes
Post by: AbbaRue on March 26, 2008, 07:32:41 PM
The diode doesn't work as a diode until a good coating of oxide forms on the aluminum.
So if you build one you have to slowly build up the voltage you apply so the oxide can build.
Also if you over drive these the oxide gets holes in it and then needs to be built up again.
The more you use these diodes the better they seem to work.

Try making one yourself, it's super easy. 
The last ones I was making used aluminum strips 1/2 inch wide and stainless steel wire.
I used them to run a 600 volt power supply because I was waiting for my 1000 volts diodes to arrive in the mail.
I made it from a plastic egg crate using 6 in series for each section of the bridge rect.

Aluminum oxide comes in different colours according to the impurities in it.
If it's red it's called A Ruby (the gem)
if it's any other colour such as blue it's called A Sapphire (the gem).
Another name for aluminum oxide is corundum.

Sapphires have been used to make radio crystals as well, but are far more expensive then quartz so quartz is use.
Probably this quality is why it works as a diode.

Title: Re: Homemade Diodes
Post by: PulsedPower on March 27, 2008, 05:25:39 AM
Interesting, sounds like it would work with any "valve metal" Have you measured the reverse polarity capacitance?
Title: Re: Homemade Diodes
Post by: AbbaRue on March 27, 2008, 07:04:46 AM
I came upon the idea from a website I stumbled upon.
I just built the diodes to see how they work and found them useful.
I haven't tried many other tests with them, but I do remember reading that this
type of diode was used many years ago before SS diodes were invented.
I think they were even used for welding machines at one time.
Perhaps I should do more study on them.
Title: Re: Homemade Diodes
Post by: AbbaRue on March 27, 2008, 07:31:59 AM
The bigger the aluminum and SS plates are the more capacitance you get,  naturally.
But I found that if the plates are to large the diode effect seems to stop.
Perhaps it just takes to long for enough oxide to form to get the effect working.
The capacitance if quite high for the size.  This is the principle behind electrolytic capacitors of coarse.
The thin oxide layer acts as the dielectric of the capacitor. 
Only electrolytic caps use aluminum hydroxide instead of baking soda and water.
At least the older ones did, maybe the newer ones use something else now.
Title: Re: Homemade Diodes
Post by: aethernut on March 27, 2008, 01:31:20 PM
The diode doesn't work as a diode until a good coating of oxide forms on the aluminum.
So if you build one you have to slowly build up the voltage you apply so the oxide can build.

It seems that you could get a coating of oxide quickly by dipping the aluminum in a solution of lye.

A related topic is Rust Removal using Electrolysis--see  At that site they post a warning about using stainless steel electrodes--Hexavalent chromate can be produced which is poisonous hazardous waste. (The electrolyte turns yellow.)  see
Title: Re: Homemade Diodes
Post by: juice on March 30, 2008, 10:12:04 PM
How would you make a homemade transistor? I guess you could manage it with mechanics or with fluids, just as you could manage a diode, but what about something in the spirit of this diode you describe? Is it possible?
Title: Re: Homemade Diodes
Post by: Koen1 on March 31, 2008, 01:06:28 AM
Hmmm... interesting idea...
I guess you could make something like a transistor,
or rather a type of "triode"...
Although I would have to think it over some more,
I would suggest one could add a thrid electrode as
"activator current" source, which could increase or
decrease the charge flow between the diode plates...
That would be a transistor-like function, in a way...
... right? ;)
Title: Re: Homemade Diodes
Post by: AbbaRue on March 31, 2008, 09:40:12 AM
I tried using 2 aluminum plates and one SS plate to get a transistor effect, but it didn't work.
Maybe I should have tried 2 SS plates and one Aluminum plate.

Has anyone reading this thread tried making one of these yet.
Just take a piece of Aluminum foil and a nail and place them in some water and baking soda.
Very easy experiment to duplicate.
Also check out this website, it mentions aluminum used for a negative resistance device like a tunnel diode:
This site has lots of cool stuff on it.

Title: Re: Homemade Diodes
Post by: pese on April 01, 2008, 12:28:55 AM
will not work as transistor
becaus that is only an dual- diode with common
cathode or anode.
Ic you have also an current from SS to next SS (in one polarity!) tham
you can try" to controle that "flow" via an "gate".

Title: Re: Homemade Diodes
Post by: AbbaRue on April 16, 2008, 07:10:04 AM
I ran these diodes for hours on end and the SSteal doesn't appear to be breaking down at all.
I believe the polarity has to be reversed for the SS to break down.
Title: Re: Homemade Diodes
Post by: Neo-X on July 12, 2014, 06:39:06 AM
I was interested on this. How can i make a homemade diode that doesnt require water? I like to make a powerfull version of radiowave cell but buying hundreds of diodes cost alot of money. If i can make a homemade diode, my ploblem will be solved.
Title: Re: Homemade Diodes
Post by: Leely on July 12, 2014, 11:39:42 AM
If a homemade diode can act as a capacitor, then it means that an electrolytic capacitor can act as a diode. Delete their capacitance by putting them in series.
It is for those who diodes is lacking.
Title: Re: Homemade Diodes
Post by: electronican on September 18, 2015, 08:42:50 PM
i found to article about tunnel diode definition and basic parameters and characteristic:
Title: Re: Homemade Diodes
Post by: electronan on October 31, 2015, 08:43:56 PM
If you need more info about tunnel diode:
Tunnel diode – semiconductor diode characterized by a small thickness of the pn junction, a very high concentration of dopants on both sides and a negative dynamic resistance for a certain range of polarizing voltages. It was invented in 1957 by the Japanese physicist Leo Esaki (hence sometimes it can be named Esaki diode). During research on semiconductor junctions he noticed their thus far unprecedented feature based on the tunnel phenomenon. This phenomenon causes charge carriers move through the narrow barrier layer at a very low voltage.
from here: (