Off The Shelf Solution for Open Collector Output to DC Voltage Conversion?

LadderLogical

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Join Date
May 2018
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USA
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4
Hi everyone.

I have a device which provides open collector GPI outputs, and I'd like to interface the GPI outputs with 5 VDC or 12 VDC inputs on a PLC. While I can certainly build my own circuitry to convert each open collector output to a 5 or 12 VDC voltage that can interface with the PLC input, in the interest of saving time and keeping the wiring tidy and organized, I'm curious if anyone could recommend any off the shelf board or device that is designed to perform this type of logic conversion. I need to perform this conversion for about 20 open collector GPI outputs, so ideally some type of board or device with multiple I/O would be ideal.

Thanks for any suggestions!
 
Hi and welcome to the forum,
With open collector outputs you will just need to provide power and a pull up resistor with the right value. You don't need any special piece of equipment.

If you look up Open Collector wiring on the web you will find lots of examples of how to wire up a pull up resistor and run it into the input.
 
Hi everyone.

I have a device which provides open collector GPI outputs, and I'd like to interface the GPI outputs with 5 VDC or 12 VDC inputs on a PLC. While I can certainly build my own circuitry to convert each open collector output to a 5 or 12 VDC voltage that can interface with the PLC input, in the interest of saving time and keeping the wiring tidy and organized, I'm curious if anyone could recommend any off the shelf board or device that is designed to perform this type of logic conversion. I need to perform this conversion for about 20 open collector GPI outputs, so ideally some type of board or device with multiple I/O would be ideal.

Thanks for any suggestions!

What sort of Inputs are you using on which type of PLC? I've seen resistor packs (DIP) for doing pull-ups on a PC board. Nothing with connections for a terminal block.

5V and 12V are not 'typical' PLC inputs. 24VDC, 24VAC, 120VAC ... are more typical and would just require a different value for the pull-up resistor.

Finally, how much current can your inputs sink?
 
I'm using two different Koyo / Automation Direct PLCs...a CLICK PLC and a Productivity 1000 PLC. For the CLICK PLC, we have a few 3.5 - 5 VDC input cards, and for the Productivity 1000 PLC we have a few 12 VDC input cards. Certainly not the most common PLC input voltages, but for our application, low DC voltage inputs are exactly what we needed.

Understandably, and as some have already mentioned, converting an open collector output to a DC voltage is pretty simple, and I'm currently doing it for a a few existing open collector GPI outputs by just using an external DC power supply and resistors. However, since I may need to perform this conversion for 20+ open collector outputs, I was just curious if there was some sort of ready-made, off the shelf board designed specifically for this purpose. I could certainly build my own multi-input adapter using a breadboard, resistors, and terminals, but in the interest of saving time, I'm just curious if something like this already exists and is available for purchase.

I believe the open collector GPI outputs are rated at 50mA, which far exceeds the very minimal current draw from the open collector to DC voltage conversion circuitry I've already made.
 
I'm using two different Koyo / Automation Direct PLCs...a CLICK PLC and a Productivity 1000 PLC. For the CLICK PLC, we have a few 3.5 - 5 VDC input cards, and for the Productivity 1000 PLC we have a few 12 VDC input cards. Certainly not the most common PLC input voltages, but for our application, low DC voltage inputs are exactly what we needed.

I believe the open collector GPI outputs are rated at 50mA, which far exceeds the very minimal current draw from the open collector to DC voltage conversion circuitry I've already made.

I ask because we use mostly 120VAC inputs, and the inputs need between 3 and 7 mA each to turn on properly. We have fixed OEM 'solutions' that had the resistor values too high to turn on the inputs properly, and we have replaced low wattage resistors after they overheated and open circuited.

I checked our installs (we have 4 that use open collector or that connect one vendor's PLC output to another vendor's PLC input) and all are terminal blocks with discrete resistors. So I don't have a vendor to point you to for an off-the-shelf solution. Sorry.
 
For the Click C0-08ND3-1, you can use the open collectors from the input to -. Just appy +5-12v to the C1 & C2 terminals, with the - on the emitters of the Open Collector device.

Same for the Productivity...
 
http://catalog.weidmueller.com/procat/Group.jsp;jsessionid=E4FA14EFA17F37A60F81282397EEE094?groupId=("group6772202724221")&page=Group
Scroll down and you will find some with resistors in there.
Others make them too, contact your terminal supplier and ask for their double decker with resistors.
 
P108nd3 is both sink and source. Any reason you can't wire it straight to the card?

The open collector output alone doesn't have any voltage on it, so the GPO alone can't be connected directly to the PLC...I need to add the voltage somewhere along the line. I've already interfaced a few of these open collector outputs with a Productivity 1000 12VDC input, so to do that I just connect a 12 VDC power supply, 2k resistor, and the open collector output in series. Whenever the GPO goes active, the circuit closes, and I get 12 VDC across the resistor. So, I just take the voltage across the resistor and feed it to the PLC input. This has been working great, but now that I want to interface an additional 20+ GPOs with the PLC, I'm just looking for some sort of board that will easily and cleanly allow me to do this for multiple open collector to 12 VDC conversions. Essentially, it would be a board with a bunch of onboard resistors, input terminals to connect each GPO, a bunch of output terminals for the 12 VDC signals to feed the PLC inputs, and a DC power supply input. I could certainly design something like this, but I'm just curious if such a device already exists.

Also, for reference, here are the specs of the open collector GPO outputs:
attachment.php

attachment.php





OpenCollector1.jpg OpenCollector2.png
 

The open collector output alone doesn't have any voltage on it, so the GPO alone can't be connected directly to the PLC...

Yes it can. The input module is the part that has the voltage on it, if you configure it for "sinking".
You are thinking "sourcing". Your output module is "sinking", and your power supply and resistor is converting it to "sourcing".
No need for all of that. The input module is sourcing or sinking. Configure it for sinking. The pullup resistor is already inside the input module, with the LED you want to turn on in series with it.

Hook it up the way Gene and AustralIan said, and it will work fine.
Or did we miss something?
 
Thanks for the suggestions. So, essentially I have three devices, with two connections each...

PLC:
PLC-C1 (common connection)
PLC-1 (input connection)

12 VDC Power Supply:
12VDC+ (power supply positive terminal)
12VDC- (power supply negative terminal)

Open Collector GPI output (as illustrated in my previous post):
GPO (collector terminal)
GPOCOM (emitter terminal)

To confirm, my understanding is that the suggestion is to make the following connections:

12VDC+ to PLC-C1
PLC-1 to GPO
12VDC- to GPOCOM

Also, for clarification and following up on Keith's last post, there's really no LED as part of my external circuitry. The image I included in my previous post is a schematic of the GPI output's internal circuitry, and only the GPO and GPOCOM terminals are external to the device. The diode / LED illustrated in the schematic is actually just part of the opto-isolator and is internal to the GPI output circuitry.

Additionally, to be specific, the input card which I am planning on using is the P1-08ND3, which is capable of sinking or sourcing inputs...
attachment.php







P1-08ND3.png
 

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