[sdiy] LEDs and noise

[Roman Sowa]

Supply the LED from + to GND and switch it on and off by shunting it to 
GND with a transistor. When transistor is off, LED is lit. When 
transistor conducts, the current flows via it and LED is dark. So for 
example if + is 12V, and resistor 10k, the current jump in power rail 
will be only about 170uA while LED current is 1mA.
You can push it one step further and add a diode or 2 in series from 
collector to LED, to only make the LED-off voltage about 1V. LED will be 
dark anyway, but current jump is now about 70uA.
Yet another step further, and supply the LED from current source. Then 
absolutely no current jumps in supply rail.

I hope that's clear, if not, I'll draw ugly schematics.

Roman

W dniu 2015-05-08 o 01:32, David Moylan pisze:
> 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?
>
> Thanks.
>
> Dave
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>