Elimination of PWM noise on LED

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hello all!

here situation: have mi pieces wired fine , working, project drives rgbw led, high power (e.g. luxeon or similar) using npn transistor wired in classical way. led ha work on same circuit of "wave shield" have optimized , miniaturized custom sd reader, mcp4921 , tda7052 amplifier wired in classical way reported on datasheet 1w amplifier so: http://www.afiata.com/tda7052-datasheet-and-circuit-audio-diagram/

now problem: sending pwm signal under 255 values makes speaker catch noise pwm signal. tried filtering amplifier did note work, plus had loss of volume. avoid solution, seeking how filter positive side of wired led (or add on transistor) rid of interference. @ moment can lower sound putting electrolitic capacitor of 470?f positive negative battery. not enough turn off sound. puting higher values not makes trick, tried. need filter takes square waves of pwm exiting led , take them flat level not make interference speaker.
how possible?

i put picture of partial schematic if need more specific ones have provide later. tahnks or hint can give me!

you need more supply decoupling, last circuit on page.
http://www.thebox.myzen.co.uk/tutorial/de-coupling.html
also layout important.


Arduino Forum > Using Arduino > LEDs and Multiplexing > Elimination of PWM noise on LED


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