Hi,
i have putting together a cnc shield and was planning to have some sort of isolation between the Step/Dir signals and the arduino.
I am a little out of my depth here but here goes.
I think i need some sort of digital optoisolation as i need to be careful of jitter due to software which means normal optos are to slow. from reading some other posts it would need to be at least 20Mbits/s.
What sort of hardware would i be looking for ?
Thanks Adam
20 millions bits (40 million HIGH/LOW transitions) per second?
That was a quote from someone who knows more than me 
As far as im aware thats correct, i have found some high speed optocouplers that can do 500kbps but this is something i have no experience with
Most of the larger stepper motor drivers include opto-isolation as standard.
What stepper motor drivers are you thinking of using?
As an Uno or Mega only run at 16MHz you don't have to worry about 20Mbit signals. 200,000 maybe - but even that would be a struggle.
...R
This is the drive im going to be using but i would like the board to be able to support different drives.
I would also like to add a bit of future proofing and make it suitable for the due.
I expect the inputs to that driver are optically isolated - what does the product user manual tell you?
…R
Logic optoisolators with >10MHz bandwidths are commonly available. I've used the ACSL-4xx0 series
before, 15Mbaud rated. But yes, stock opto's are very slow photo-transistor outputs, not high-speed
photodiode+schmitt-trigger.
There are many others and there are also RF galvanic isolation devices like the ISO734x series, again
rated to 25Mbaud - these use a high voltage capacitor rather than an optical path to give isolation.
Hi,
If you download (try google) the manual you will find that the inputs are already opto-isolated.
Tom.... 
Manual attached.
Leadshine DM542.pdf (340 KB)
TomGeorge:
If you download (try google) the manual
The reason I did not bother to suggest that to the OP is because there is a link to the manual on the web page in his link in Reply #4
...R
