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USC-B10-T42 Digital Input Bits Not Updating


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I have a 24V supply on a din rail setup for the PLC/some proximity sensors.

I have the V+ connected to the brown wire for the sensors, the V- connected to the blue wire, and the black signal out wire for the sensor is connected to I0 on the PLC.

The COM0 is wired to the V- from the power supply as well. The proxy sensors switch/light up correctly and I can see 24V at I0 when i probe I0 and COM0 with a multimeter.

The PLC input LEDs don't light up when the switch provides 24V to the input nor does the bit toggle in the software.

Is there a wiring/software initialization step for the inputs I may have missed?




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I have the power connected from the supply to the V+/V0/ground on the PLC controller terminal.

I also have a V+/V0 connection to the onboard digital outs via terminals 1 and 2 on that side.

Do the on board inputs require an additional power connection? If so I do not see terminals called out for that.





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Looking at the Installation Manual for the USC-B10-T42, Page 10, the wiring you described is for Input wiring, sink

Note the description for sink in the note below :

          Use sink input wiring to connect a sourcing (pnp) device.

From this, you have the Inputs wired for PNP Sensors ( and your meter reading appear to indicate PNP  -- assuming the 24 VDC input  is when the sensor is sensing a target)

Are your sensors  PNP or NPN  ????  -- Make and Model



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PLC model is in the post title (USC-B10-T42) and I'm only using onboard I/O, no additional modules.

The 3-wire proximity sensors I'm using are PNP. From SMC and the P/N is D-M9P. 

I currently have V0 from the power supply connected to the COM0 port to set the inputs up as sink wiring for pnp sensors. So, when sensor sees the actuator piston, it lights up and I measure 24V between the black signal wire and the COM0 terminal. However, the input status LED does not light up on the PLC and the bit in the software does not toggle to 1.





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