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Digital noise in my circuit

Hi. I've built a servo controller. My controller send a +/- 10V signal to a servodrive. So the simple cable wiring (from my controller to the servo-drive) is CMD+, CMD-, ENABLE and GND. When I enable the drive and probe the VCC on my board I see regulat *spike* of about 250mV to

400mV p-p, sometime more. This noise is exactly the PWM frequency of the servodrive: 20 KHz. My controller work well, but I'm still a little bit worry about this noise. If I disable the drive, all this noise dissapear. By the way, the servo drive work on 80Vdc that I built with a basic transfo/bridge/capacitor and my board get is VCC from a switching power supply. My own power supply (80Vdc) and the switching poer supply a both connected a the same point to the 115Vac.

So my questions is:

How this noise get to my board? By the GND wire of my cable (controller servodrive) How do I reduce that to a safe level (what is safe level, maybe 50mV p- p)

Reply to
reginald.louis
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use a reactor on the output or input ?

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http://webpages.charter.net/jamie_5"
Reply to
Jamie

There is a chance that this is caused by the long ground lead on your scope probe. If the ground lead on the probe is more than 5mm, you can pick up all sorts of radiated noise via the ground lead, even if the signal you're observing is "clean". See if connecting the ground ring near the probe tip directly to ground helps.

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Mark
Reply to
qrk

Use both channels of the scope in the differential mode.

Bob

Reply to
sycochkn

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