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Topic: AVcc low pass filter required? (Read 1 time) previous topic - next topic

Tumbleweed

Hi,
I just built my first breadboard Arduino (after I smoked my first Uno, 328 was still good). According to the tutorial I followed, to make use of the ADC, I need a low pass filter on pin 20 of the Atmega328 (AVcc)to get rid of power supply noise. Is this necessary? My o-scope shows only a few micro-volts noise even before plugged in to the two caps on the power input cicuit, I can't find anything after them.
I want to use an analog accelerometer, not that critical as far as noise goes. If I will need it, any links to a schematic? Or just design my own for transient 60hz noise?
Thanks,
TomJ
Einstein once said you don't really understand anything until you can explain it to your Grandmother

retrolefty

#1
Mar 05, 2012, 12:50 am Last Edit: Mar 05, 2012, 01:13 am by retrolefty Reason: 1
Very few arduino type boards or clones use a low pass filter to the Avcc pin, they just normally wire it to the Vcc pin with a .1ufd bypass cap to ground for some noise filtering. The AVR datasheet for a 328p chip does show a typical and recommended cap/inductor filter for the Avcc if you require the improved noise filtering method. It's up to you, most normally don't see the benefit in most applications.

Lefty

CrossRoads

If you're not doing audio work, you can probably get by without it.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Tumbleweed

Thanks fellas,
Nice of you to reply so fast.
TomJ
Einstein once said you don't really understand anything until you can explain it to your Grandmother

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