Go Down

Topic: Elimination of PWM noise from TLC5947 LED (Read 1 time) previous topic - next topic

mitchjs

to test this i have < 4" of wire...
yes, less leds = less noise, im sure due to less current being drawn
maybe an inductor would help, shame i got nothing really laying around
that could handle the current, ill have to look... just a few leds connected
to see if it help

ill let ya know, soon... me just got home... play time in a few

thanks!!!

Grumpy_Mike

Quote
im sure due to less current being drawn

It is probably more to do with the radiated interference from the wires than current from the supply.

DVDdoug

An inductor is a good suggestion.   Without an inductor, the capacitor is basically trying to filter the entire electrical system.

A diode can sometimes help too...  A diode prevents the capacitor from discharging into the entire electrical system, and it blocks positive noise spikes.  But you will loose a little voltage across the diode, and your LEDs will be dimmer, assume they are running off the 12V).

mitchjs

well...

i made a small board that put inbetween my 12v source and the 12v input to the led chain
i feed 12v though a 330uH coil (only thing i could find), then i got 470uf electrolytic and a .1uf ceramic in parallel
does make a big difference, i dont think i hear any difference with out the coil, too hight uH?


any one ever mess with a Murata BNX012-01?
http://www.mouser.com/catalog/specsheets/Murata%20BNX%20Series.pdf

i need to get this now actually in the vehical, to see(err hear) if it makes enough difference

scope still shows the noise, but much less amplitude, and less spiky

mitch

Grumpy_Mike

Quote
i dont think i hear any difference with out the coil, too hight uH?

No too low if it is doing nothing for you. You can't have it too high.

Go Up