Hi Edson,

I found in my power supply project that the PIC's ADC is susceptible to
picking up the PIC's own clock signal as well as other noise. I placed an
RC low-pass filter on the input and it solved my fluctuation problem. What
is the source of the voltage that you are feeding to your ADC?

If you have a relatively high source impedance (several K) then you should
probably buffer it with an op-amp in the non-inverting follower
configuration. Then, on the output of the op-amp place a 2.2K resistor
(between the ADC and the opamp) and then from the ADC input to GND, place a
capacitor. What value cap depends on how fast you need your ADC to respond.
Take the highest frequency you want the ADC to respond to, multiply it by
ten, and then plug it into the formula: C = 1/(6.28*f*2200), this will be
the cap value in farads.

If your source is already less than a few K (I'd say less than 5K), then
you can probably just eliminate the op-amp.

Sean


|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
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