Hi,

I have an old machine with an old set of servo drives that I am trying to hook up to a modern machine controller. My issue is that the drives take a differential speed control signal. My controller provides a single analog signal of +-10V on a given axis channel.

Please see the links for a snip of the servo drive schematic:
http://imgur.com/a/OdNVd
http://imgur.com/2OE92mV

I would like to connect my controller's analog output (+-10V) to the auxiliary input of the servo drive. I believe from different things I've read that these servo drives (old Servomates) accepted +10V and -10V on the S1A and S1B differential inputs.

Also, I have the opposite "problem" on my encoder feedback. I have an encoder with single ended outputs from A and B. My controller needs a differential input for the encorder (A+, A-, B+, B-). I know there are single ended to differential signal converters, but I'd love some advice on an inexpensive solution that won't require me to build circuitry around it.

Thanks in advance!

 

You may be able to run the signals single-ended, i.e. connect the servo minus differential inputs to your speed controller common, and the controller minus differential inputs to the servo drive common.

This is a typical way to minimize the effects of ground noise between circuits even if you don't have differential output signals.
The differential input cancels any differences in AC or DC ground voltages between the two.