Open Collector Output interface to 24V Digital Input, Inverted

Question

I have a stepper motor (multi-axis' in fact) that provides a limit signal (E11 NEGATIVE LIMIT) that is open collector output:

I need to connect that signal to an opto-isolated 24V digital input (no internal pull-up resistor I assume):

Currently there is a circuit board installed that does this, and that contains:

A regulator IC for 5V
A pullup resistor circuit to 5V.
An IC (ULN2003 Darlington Array) to up the voltage to 24V and
An IC (Philips 74HC14N74HC14N HEX INVERTING SCHMITT TRIGGER to invert the signal (to active high instead of active low I assume)

I want to eliminate this custom made circuit board and use "industrial-strength" off-the-shelf DIN rail mounted items to interface the motor limit output with the digital input.

I'm a mechanical engineer and am kindly requesting some advice how to do this professionally, without custom circuitry.

Thanks in advance.

Tom.

peteroakes · Accepted Answer

2 diodes, 24V and no resistor will release the magic smoke for sure. the resistor is to limit the current through the opto LED as much as it is also a pull up if the input to your monitor (PLC) is also an opto isolator input then you dont need to drive it with 24V If it is already 24V capabable then it probably has a resistor or other current limit in it already so the open collector from the stepper should be able to be directly connected

dougw · Answer

You could connect a Phoenix Contact 2900353 to the E11 signal, but that signal needs a 390 ohm resistor between it and 5V.

The polarity can be reversed simply by connecting the module slightly differently.