Need help connecting open collector output to PLC input.

[plclurker]

Hi,

I have a Micrologix 1400 with a 1762-IQ16 discrete input module, wired for sinking inputs (common to DC-)

I have an instrument with the following outputs. (I plan on using the solid state relay for some low speed counting). Everything on the top side of the terminals is internal to the instrument.

If I were to use the common collector output instead, how would I connect to the PLC's discrete input? The emitter does not appear to be internally grounded within the instrument, so could I connect the collector to +24VDC, the emitter to the PLC input, and allow the transistor to pulse 24VDC into the PLC input? Or would I have to wire the PLC input as sourcing?

If a pullup resistor is sized, the input impedance of the IQ16 inputs is only 3kohm? WTF? That would have to be a pretty low pullup resistor.


Thanks for any help.

 

[tarik1978]

Please have a look:

http://www.ximea.com/support/wiki/usb3/Digital_Output_Wiring

 

[JRB]

...

 

[plclurker]

Wow, excellent! Thanks, JRB.

 

[mi_scott]

Need help connecting open collector output to PLC input

I think you would need to wire any typical input cards (PNP sinking) with a "pull-down" resistor instead of the pull-up. What I have done in the past is wire a terminal strip, single-pole, single-throw relay with 24VDC on the A1 side of the coils with the A2 side going to the open collector and the other side of the open collector going to ground. A dry contact of the relay is then used like a typical limit switch contact to the PLC. More straightforward and simply terminal-strip relays aren't much more expensive the the terminals themselves. I don't like seeing resistors in terminal boxes.

 

[L33er]

(PNP sinking) ???