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I'm controlling a 12v RGB LED strip from an Arduino Mega following the tutorial here

I'm controlling with 3 pots via the Mega's ADC >> PWM value written out using analogWrite(LED_PIN) & everything works fine or so I thought!

In addition I have 3 servo motors that are also controlled by another 3 pots these also worked well when tested without the LED driver attached. As soon as I wire up the LED driver there is a crazy amount of noise generated that feeds back into the servo control that manifests as random jittering of the servos.

I have tried putting a number of different capacitors (basically whatever I could find in the cupboard) across the 12v - ground rails. Which do seem to filter out the higher harmonics of the noise but to get the noise (and the servo jitter) to disappear I lose servo response to their control pots.

I've also tried a couple of moving average algorithms in software whilst they do have an effect they by no means filter out enough of the noise.

So is there a way of filtering out this noise without compromising the servo control?

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  • \$\begingroup\$ Have you considered two separate 12V power supplies? \$\endgroup\$ Oct 26, 2019 at 14:07
  • \$\begingroup\$ yeah but dont really have the space \$\endgroup\$
    – DrBwts
    Oct 26, 2019 at 14:32
  • \$\begingroup\$ Add an LC filter on the power going to the LEDs? Try a small ceramic like 1000p across the pot wiper and across the servo output signal? Try shielded cables? \$\endgroup\$
    – MadHatter
    Oct 26, 2019 at 14:50
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    \$\begingroup\$ Can you upload a picture of your setup and schematic? \$\endgroup\$
    – bobflux
    Oct 26, 2019 at 14:53

1 Answer 1

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I've two suggestions for you.

1) Run separate power and earth wires (as thick as possible) between the power supply and each of the LED and servo driver boards so that they don't share any power wiring.

2) Get a couple of large ferrite beads designed for noise suppression and thread each of the supply wires through them, maybe 2 or 3 turns.

If you add your capacitors it would probably be best to add them to the driver board inputs as the PSU output will most likely have built in capacitors already, or at least will be low impedance.

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