>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>Sent: 22 June 2006 10:42
>To: Microcontroller discussion list - Public.
>Subject: [EE]: ICD2 introducing noise onto +5V line
>
>
>Hi,
>   I'm trying to sort out a problem with my homebrew battery 
>charger, which 
>seems to only occur when it's hooked up to the ICD2, and even 
>then it only 
>happens when the ICD2 is hooked up to my desktop machine.
>
>   When the ICD2 is connected, the +5V power bus picks up a 
>0.5V amplitude 
>repeating pulse, with a period of about 100us. Unplugging the 
>ICD2 from the 
>PC, or plugging it into a laptop instead of the desktop system 
>completely 
>removes the noise.
>
>   Besides "use the laptop", can anyone suggest a way of 
>getting rid of this 
>noise? It's causing major problems with the opamps in the V/I 
>sense circuit -- 
>the noise is going from the Vcc supply to the opamp output. 

Sounds like you have relatively poor supply rejection?  Is one of the inputs referenced to the Vcc rail?


>   Short of giving up on debugging this thing with my desktop 
>machine and 
>switching to the laptop (which would involve me reinstalling 
>MPLAB), can 
>anyone suggest anything else I could try that might get rid of 
>(or at least 
>severely attenuate) the noise?

Have you tried using a serial connection to the ICD instead of USB?  You will need to plug a 9v supply into the ICD though.

Regards

Mike

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