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)