> -----Original Message-----
> From: piclist-bounces@mit.edu 
> [mailto:piclist-bounces@mit.edu] On Behalf Of Drew Pilcher
> Sent: 16 June 2009 02:03
> To: piclist@mit.edu
> Subject: Re: [EE] Interference problems in a PIR amplifier
> 
> 
> Thanks for the advice.
> 
> I added all of filters you guys suggested but the pulses 
> still come through, the only thing that was able to remove 
> them was running the PIR and PIC on completely different 
> power supplies, the noise even crossed between the 12v and 5v 
> rails on the ATX. I currently have all of the following 
> applied simultaneously.
> 
> switched to a 6v wallwart and 7805 with a decoupling cap 
> across the input and 470uf accross the output
> 
> diodes and caps to ground isolating each of the circuits from 
> the power rails, plus a 220ohm in series with the diode on 
> the PIR side as Jinx suggested.
> 
> .1uf decoupling caps across both ic's power pins as well as 
> across the PIR elements refrence pin and between the pir 
> elements output and ground
> 
> a 2 pole filter in series with the pir element's #1 pin with 
> the values Spehro suggested (eg. 10K/220uF + 10K/100uF)
> 
> a bridge accross the led, to rule out optical interferance

Did you try decoupling the Vss/2 bias divider as I suggested?

Regards

Mike

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