Reading pots noise

[leetut]

I’m trying to read the fv1 pots using a microcontroller but I get noise into my audio signal, is there some way to isolate the noise, tried a choke, and resistors with no luck

Build docs:
https://www.dropbox.com/sh/yyp7xwoc0zal ... 6WA_a?dl=0

[frank]

You have the FV-1 between two digital boards that are probably radiating lots of RF and it is getting picked up by the FV-1. I would use a larger enclosure, move those boards as far away from the signal as possible, add shielding, etc. Go to a 4 layer board and make a good ground plane and power plane.

[leetut]

I currently have the screen and micro controller on a breadboard, connected to a pcb with only the fv1 circuit, the noise is coming from the connections to the pots, it goes away if I disconnect them

[frank]

You have really no ground plane and that tends to mean noise. Bypass caps need to be right at the pins of the chips. Without a pdf schematic I can't tell what the power is like as we don't use Eagle. Always use 4 layers for a mixed signal board like this with solid ground and power planes otherwise you will have ground loops and noise.

[ice-nine]

I have noticed in your PCB pictures that you have cut off the pot mounting solder tabs and placed foam pads under the pots to hold them in position, while this may or may not be a problem the solder tabs are electrically connected to the pot shaft and provide shielding and really should be soldered to the pcb ground plane.

[ice-nine]

I have just had a quick look at the schematic and the board and it looks to me that you have the pots connected to the FV-1 in the normal method and also connect the wiper to the micro, would it not be a better idea to read the pots into analogue inputs on the micro then send to a PWM output which drives the P0-P2 pins. You would need to filter the PWM output from the micro before the signal goes into the FV-1 pot pins.

Out of interest I wonder if the noise goes away if you remove the wiper connection to the micro from each pot?

[leetut]

the noise is only an issue when mix and volume are maxed, it’s fine at unity gain, and I think it’s just a mixture of the things frank mentioned, I’m leaning towards a bigger box and separate boards for my next project