Quote Originally Posted by thjremy View Post
Hi,
Your board looks OK... But the Photocoupler you chose are too slow. 18us for rising time and 18us for falling time... 36us total or a minimum pulse with of about 40 / 45us ... You won't be able to pulse faster than: 1/45us = 22.2KHz Mach3 pulse at 25KHz minimum...

See datasheet page 2: http://www.if.pw.edu.pl/~alice/DAC/pc847.pdf

RNR