Quote Originally Posted by Kitwn View Post
Maybe I should try designing that low cost DIY optical fibre interface that would allow the motor drivers to sit next to the motors and no long wires through the machine except power rails. Well we must keep the old brain busy during these long spells stuck at home..
The first time I attached a scope to my spindle encoder on the lathe my jaw hit the floor with the noise from the 3-phase motor, so I appreciate where you're coming from. I'm surprised you're seeing that behaviour on short cables though comms theory was never my strong point - I'll believe your experience over my memory any day. I still think using cheap (or expensive!) BoBs with opto-isolated inputs offers a lot of advantages, if only for the pathetic frequency response that will filter any amount of HF noise as well as providing much better noise immunity level than HC-series logic.

In my case (the spindle encoder) - the design of the 7i76e Mesa card is intelligent and offers a differential input for shaft encoders with 130R input, which allows easy connectivity to a RS485 driver to allow transmission over a balanced twisted pair - helped massively. I appreciate this doesn't work in your case.