Voltage regulation circuit 12V to 5V in 5A range

[amgen]

Right now I'm just basking in the glory of having found the root cause of most of that noise on the lines, and started looking for a source of affordable "good" 9V 5A power adapters.

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not trying to 'rain on your parade'..... it is possible that isn't where your noise is coming from...... if you haven't already, put a 10 or 100 microfarad electrolytical and a couple of .1 or .01 microfarad caps at the output of the power supply..... and I didn't look to see but you would want to put the same capacitor duo on each separate circuit board..... that SHOULD squash the noise. Plus..... a bunch of interconnected grounds running here and there are often culprits for noise. And keep in mind that often serious engineers and engineering is involved with noise and interference

[Ioannis]

Also breadboards are the worse for low noise circuits!

Ioannis

[Demon]

VDD with all ADC pots OFF; VDD is super stable.




I control the contrast on all 4 LCDs with PWM on a 2N2907:




Guess what happens to VDD when I turn up the contrast:

[richard]

that seems a strange way to control the contrast.
how does it go if you set the contrast the normal way ?


anecdotally contrast by pwm needs a substantial LPF otherwise all sorts of nasty artefacts are introduced

perhaps a schematic would enlighten things

[Demon]

that seems a strange way to control the contrast. ...

Sorry, contrast is hardwired to prevent the user from burning out the LCD. It's the backlight that's PWMed.




Backlight is controlled by PWM from a 2N2907A because it controls the 4 physical LCDs simultaneously as well as the radio in-game via USB:

[Demon]

I'm waiting on some IRF5305P hexfets to replace the 2N2907A. Hopefully they're less noisy.

[richard]

does that drive all four backlights ?
where does led cathode go ?

if the cathode goes to vss then no wonder its noisy
the fet should make it worse