One solution if the power spikes are short is to put smaller bypass capacitors as close to the load as possible.  These provide the current when it's needed most and then 'recharge' from the main supply between spikes.  You might experiment with 0.1 to 1 uF capacitors at the gumstix power connector and at the power connector to your load.

Small capacitors liberally used at all the power/ground 'load' points allow a great deal of energy to be stored without the need for large bulky capacitors but work best if the load spikes are very short like the switching load of electronic circuits.

Lawrence

ken staton wrote:
On 6/13/06, Grahame Jordan <gjordan@geicp.com> wrote:
  
Hi,

This is an electronics question. I hope someone can help.

I have a problem with my motor controller.
http://www.pololu.com/products/pololu/0205/

I am not actually using a motor but a resisitive load.  When the PWM really
starts working I get an increadable amount of noise on my power lines such
that it locks up the gumstix. More than 4V peak to peak

3.686400 MHz / 375 = 9830.4 Hz - Maximum is 10Khz for VHN3SP30

Which just happens to the the frequency of the noise.
The higher the current I draw the more noise.  This is obvious.

I can aleviate the problem greatly by putting a big electrolytic capacitor
across power to ground 4700uF say. Now the noise is ~ 1V - 0.6V peak to peak
and the gumstix runs OK.

Is there a better way of filtering this noise
    


This topic keeps coming up. I've drawn some pictures to illustrate the problem:
http://pubs.gumstix.com/documents/app_note_2.pdf

Regards,
Ken


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