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ahuat

open collector need 2 power supply?

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Dear All, I try to connect a NPN open collector device to CJ1M CPU 22 as high speed input, further reading in the manual : cat W395-E1-03, page 32, shows that for such kind of device the system need two power supply. Is it ok if i use only 1 power supply 24 VDC, and connect terminal + of sensor device and IN ( 24VDC )? I think the reason why omron give a 2 power supply schematic is if the sensor need different voltage for power supply, am i right? Regards ahuat

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That must be the reason as I can't think of any reason why you could not use a common power supply for both the sensor as the input unit, although it is NPN.

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no... they are both 24V, BUT input is open collector NPN and mentioned PLC input is expecting PNP (+24V as signal). if you use THAT circuit, you sure need two power sources and they have to be isolated from each other. on the other hand, you COULD choose to simply reverse polarity of that output, (this is what i would do, i don't like multiple power supplies either) then just sit and pat yourself on the back. all you need is small device that changes output polarity, for example phoenix contact 2964319 is small, inexpensive, it can also be used for reverse polarity to convert PNP to NPN and it's good up to 15kHz:

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I was asuming it was concerning an NPN input, but of course with an PNP you need either a separate PSU or a polarity changer like you mention. I would prefer that over a separate PSU as well.

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The CJ1-M built-in inputs can be arranged to accept inputs fron NPN or PNP devices just like standard Input modules. The only difference is that each of the 10 inputs can be configured as NPN or PNP inputs Each input has three terminations. 24VDC, LD+ and 0V/LD-. Use LD+ for the input from your external device if it is PNP sourcing type, wire your power supply common to 0V/LD-. Use LD- for the input from your external device if it is NPN sinking type and wire your power supply positive voltage to +24VDC. If the +24VDC terminal is connected to your power supply then use the 0V/LD- terminal for the input. If the 0V/LD- terminal is connected to your power supply common then use the LD+ terminal for the input. For example for IN0;- Connect +24VDC to Pin 1 [A1]. Terminate Input on pin 5 [A3]. Input is ON when external device is 0V. OR Connect 0 VDC to Pin 5[A3]. Terminate Input on pin 3 [A2]. Input is ON when external device is +24VDC. Don't understand why you feel you need two power sources?

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Probably if the sensor need other voltage range ie 12 VDC or 48 VDC? and... seems like CJ1M built in IO only accept 24VDC, then one must use 2 power supplies. For similar voltage range ( 24 VDC ) i think we can use only one power supply.

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Corrections above to one of my previous posts. Apologies for error. LD+ and LD- = LineDriver+ and LineDriver-

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