Pseudo-Theremin - A demo using electrical noise of floating A4 pin

Hex File

This is an experimental program using electrical noise of floating A4 pin.
It shows analog value of A4 pin as graph and sound.
If you add electrical noise to A4 pin, graph and sound change.
For example, rub around on 32u4 micro controller chip.

Yesterday I read this.
I didn’t know this:

A4 is used to pick up electrical noise as a floating pin, for the initRandomSeed() function

And it is very interesting to me, so I developed this experimental program.
I thougnt that maybe this electrical noise can be used as 7th input device.

I used Arduboy Lib instead of Arduboy2 Lib, because there is more noise when using Arduboy2 Lib.
I don’t know why Arduboy2 Lib is more noisy.


You could also try A5 to see if you get a better or worse or different signal.

Even the D-Pad button pins could be used if you disable the input pullup on them. Pressing the attached button would short the pin to ground and stop the noise, but the pin would be floating while the button was released.

A0 = Up button
A1 = Right button
A2 = Left button
A3 = Down button


Thank you.
I did’nt know about A5 pin. I will try to experiment about it.
And it is very interesting about D-Pad button pins.

You can disable the input pullup on a button pin by setting the pin to INPUT mode:



Hex File

I tried about all of analog pins.
Uploaded A3 version, because down button is most easy to push in D-pads.

A5 is similar to A4, but more noisy.
A0 - A3 show small sine curve as usual.


For some reason I want it to create something like a static electricity detector (probably would not work) or a vibrate sensor (probably will not work eiher)
If you would have to take the Arduboy apart (just the case) you can find LOTS of pins behind that big, untra-thin slab of battery, and one of them seems to be unused. I have some crappy electronic parts where I have the skill to solder onto and maybe that will improve this random generator? IDK but if you can spend like less than half an hour doing the favor, then I might just in turn have something to give.

1 Like

Actually if you can, grab a AVALANCHE DIODE and get it onto the Arduboy.
Let’s say you are watching TV, and somehow the TV signal was lost. All the random “snowflake” on the screen and the speaker was from that little thing called AVLANCHE DIODE.
Instantly thinking about the nearest hardware store…

1 Like

Thank you.
I didn’t know about AVALANCHE DIODE, so I looked up in Wikipedia.

Avalanche diodes generate radio frequency noise.

It seems interesting.

Actually it is like most of the small things you can find you do that are not really accurate will do.
If you were to ask what I am thinking now, I am thinking about crappy resistors around 50 uf (they will loose their charge in like a millisecond) and I assume that will also be a fun thing to explore.
Maybe some heat resistors…

1 Like

Actually since I covered mine back up as it was shipped (plastic foil on front and back) I have no access to the metal back and therefore the only “electrostatic” noise I can generate was by “pressing” the cover where the Atmel chip sits. Pressing the cover sounds fine, but if I was to create something shown in your animation, then my Arduboy will probably be dead.
Accessing the back (probably GND) very important in this case?

1 Like

dead? oh!
I’m not good at Electronics, so it needs advice of someone else.
Maybe this demo is bad for Arduboy, because electrostatic gives bad influence to Arduboy.

No. Electrical noise and or static charges will be there whether you read the pin or not. Running the program causes no more danger than what is there all the time. If you don’t open up your Arduboy the danger is extremely small.


No it is just that if I was to create what is shown in your gif without access information the CASE (I covered the rear case up in plastic foil) so the electro static noise generated will be in much smaller value, and mine was basically a pressure sensor since there are no other way to introduce a change in electrostatic noise other than bending the PCB (printed circuitry board) in this case.

I was not talking about opening it up, although I already did so like the second day I get it to measure the battery…
And someone who does that’d better think FIVE TIMES about his soldering skills before taking any action (even a person who had put together a drone, which is me, who also have skill in soldering (I never need or have a “third hand” in assisting, yet I join wires and do other things nicely)) had not done so for now, and is UNNECESSARY-grab a Arduino…Tiny and smack it onto a breadboard, and…well, have fun with that.
I meant the aluminum back cover
It is probably that (but that is NOT supposed to connect to the board by any measure…without me touching it there will be little electrical static noise.

1 Like

I doubt a static charge will affect the signal much. It might add a bit of DC bias. It’s Electromagnetic interference (EMI) that is picked up as a varying voltage on the pin.


I know because supposedly it is SEPERATE from anything that consists of more than 0% metal, be it gold, copper, silver, iron, steel, aluminum, whatever-num.
BUT if you are doing things with those plastic shirts rolled THREE TIMES around it it will probably not work anyway (I will tear them away after my first game got posted)

is there a way to suppress the sound without it making the wave seem more bland?

Making it more quiet? Or complete elimimate it?
I was usually doing things when my dad is in his room with both door open, so I will just comment out the code that do things about the sound.

when i commented it out it seems more flat, less moving… do you know why that is?
is it because the sound output has an effect on the static?

1 Like