I have a CNC system that consists of a CNC controller connected to a PC via USB. The controller is in turn connected to a stepper motor driver board. My problem is that some time the turning off/on of the stepper motor drive power supply induced larges spikes in the power distribution of the CNC controller, some times to the extent of resetting the system.
When the drives are switched on you can even see the 20khz PWM frequency of the drivers switching on/off on the CNC controllers power distribution as thin voltage spikes. If the drivers board is disconnected from the controller board there is no interference.
I am assuming that since both boards are connected with a common ground that this is the main cause of the induced spikes. Also the CNC to driver interface is via digital isolators, so in fact the CNC board and driver boards are electrically isolated.
I would like to know what I could do to minimize this problem. Any suggestions are greatly appreciated.
The controller uses the USB power supply and is isolated from the drivers. But only when the drivers are connected to the controller do I see noise being injected into the controles (usb powered) power supply.
A diagram to illustrate the architecture: