Dynomotion Forum

I am upgrading my limit switches to 5 micron accurate limit switches from Metrol. They will be 24vDC and interfaced to the Kanalog opto isolated inputs on JP15. See attached PDFs for the switches.

These switches have an LED in series without any current or voltage limiting included. Metrol suggests a 2K resistor to be added in series for a 24vDC system. Something like this (my note of opto terminals in red):
Per the spec's for Kanalag, I noticed the opto inputs already have a 10k resistor in series

Opto Isolated Inputs = (8) 3-24V input, internal 10KOhm series resistor

Does this mean I will not need the addition of the 2K?

Thanks.

Yes. Their LED may not glow or be very bright but the circuit should function. You might put like a 3K ohm resistor in parallel with the Kanalog input if you would like their LED to glow brightly.

Thanks, Tom. That was what I was thinking too. I do not really need the LED indicator. They will be hidden after assembly anyway. I would have simply ordered the non LED version if they were in stock.

Have a good weekend!

Tom,

An update on these Metrol limit switches...

The LED lights up plenty bright without adding any additional parallel resistors. The onboard series resistors on Kanalog do the trick without any extra mess!

The switches also seem well under the 5 micron repeatability for now.

Cheers!

Good to know.