Permanant hiss in output
Opened this issue · 4 comments
Me again,
i am getting a rather noticable but quite annoying med high frequency in my output (f#'').
When I decouple it with values bigger then 1uF it gets completely filtered out but the overall tone is too muffled.
Do you have any further ideas? Can you reproduce it? Where is the hiss produced....
PS: Doesn't make any difference if I run it from PSU or battery
Cheers,
Jörg
OK, i figured it out, in case anyone else also has this problem here's the solution:
I don't know why but the source of the hiss is the matrix display and to get rid of it i simply removed (!) the GND cable from the matrix-board, leaving just the 100uF between VCC+GND. The display is still fully functioning..
uhm ... same problem. I tried @mayasfinest solution but nothing ... it doesn't work, hiss doesn't go away.
I listen this background noise also in some videos on youtube, so I think that someone else has this problem
Does anyone find a solution?
Hi, yes the matrix can cause a lot of noise due to the LED scanning frequency switching. Not sure @mayasfinest solution is a legit electronics solve (!🤣) but generally the noise can can be reduced by:
- increasing decoupling capacitance next to the matrix
- making sure your power supply is clean (although I'm surprising that it happens with battery)
- powering via the arduino's Vin instead of via the arduino's USB port
- increasing the value of the iset resistor on the MAX7219 matrix driver - you can safely increase this to 100k from the default (usually 10k). this will reduce the peak current draw of the matrix and therefore reduce the ripple noise on the 5V line. you may even be able to increase this to 400k and then use leddisplay.setIntensity in firmware to increase the duty cycle to max which would maintain matrix brightness with less switching noise. I'm using 100k at the moment and the display ranges from quite dim at min intensity to still really bright at max.
Thanks @Meebleeps i'll try your suggestions!