[sdiy] LEDs and noise

Nils Pipenbrinck n.pipenbrinck at hilbert-space.de
Fri May 8 18:56:29 CEST 2015


On 05/08/2015 01:32 AM, David Moylan wrote:
> If you're dealing with a lot of "blinkenlights" what's the best way to
> handle them?  Is it better to power them between the + and - rails or
> from one rail to ground?  Is it worth using a "dirty ground" scheme, or
> is the noise induced on the supply rails itself?

How about avoiding the noise at the first place? If you don't just
toggle the LEDs at highest speed but limit the slew-rate of the LED
current you get much less high frequency current spikes that could feed
back into the rest of your system.

If you control your blinkenlights with a known frequency (e.g. playing
back movies on a large LED panel or so) the switch frequency becomes
predictable and you can use a tuned CLC or Pi-filter between the display
and the other part of the system.

Thanks to the widespread use of dc:dc converters inductors are easy and
cheap to get these days :-)


Best,
  Nils












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