Quote Originally Posted by JAZZCNC View Post
I wouldn't take that route.? The drives are industrial grade and servo's are powerful beast's that unlike steppers tend not to stall when the shit hits the fan.!
For this reason things like limit switch's and E-stops become very important with servo's. They are sensitive to electrical noise and for this reason I wouldn't run any e-stop or limit switch's with 5V, instead using 24V which is more industry standard. So you'll need a 24V PSU so then I'd run the BOB from that, most decent bob's will run off 24V.
I wasn't suggesting he drive the CNC M/C side of the BoB from the PC. Only the PC side of the optos would come from the HDD 5v. I'm sure your PC wouldn't want you to put 24v or more up its paraport. As I stated the EL817s provide the isolation; on this BoB inbound and outbound, so your e-stop and limits etc. can go up to, say, 30v.