High-speed optical coupler


Thread Starter

George Kaufman

We need a high-speed optical coupler to interface any PLC with 24VDC outputs to a servo drive with pulse and direction inputs.

The drive input is internally pulled up to 5 VDC with a 1K Ohm resistor. However, there is also about a 1.5K Ohm resistor that internally goes from the drive input to logic common. So there is about 3 VDC from the drive input to common with nothing connected to the drive. We need to pull the drive input to common with an open collector from a opto-coupler module (the input to the opto-coupler is the PLC output). We tried a Phoenix Contact DEK-OE-24DC/24DC/100KHz but the output transistor would not turn on enough to pull the drive input to common (we hooked the drive input to output terminal + and drive common to output terminal 0). The minimum operating
voltage for this item is 4 VDC so that may be the problem.

This is a very common requirement for us and we would like to have a standard interface opto-coupler module that we could recommend for this
application. The drive can accept up to a 600KHz pulse frequency but an opto-coupler module that can operate up to 50-100KHz would be enough for
most applications. Any suggestions?

George Kaufman
[email protected]
You could try Opto-22 G4 style I/O modules. They have a two high speed modules, one of them should be fast enough for you. Check the turn on and
turn off times. I seem to remember that one of them was in the xx microsecond range. Use their G4PB4 4 position mounting rack, I think.

Bill Sturm
We have done this on several occasions using a DIN Mounted opto coupler by Continental Industries. Part # ODC-060-RM I believe. This is plenty fast as we have additionally used it to buffer the marker pulse from an optical encoder to several other circuits to facilitate hardware latches of multiple encoders all at the same time. Using the ODC series (DC output) for inputs works better for high-speed applications because they typically do not use LC filters that are often used in the DC Input modules.

Best Regards,

Ken Brown

Applied Motion Systems, Inc.
Voice 360 686 1133
Fax 360 686 1166