photo sensor problem

hey guy , I'd really appreciate the help on this.

so I have a photo sensor ( hanyoung pu-30 ) and it's rightly connected but the signal wire when it's true gives only 10 volts or less when it's connected to the plc although when I measure it outside the plc it gives 24 volts the problem is the plc can't the read the signal the sensor is giving. is it because the plc won't sense the signal because it's much lower than 24v or is it the programming?

and if it's the programming is there some kind of a trigger used to trigger these kind of sensor. P.S. I am using lenze drive plc EPL 10200.

I used the same trigger I used for proximity sensor which works fine , does it matter?

and the strange thing is that another photosensor just like this one works on the same plc with like 9.5 volts as input to the plc and the sensor works fine.

thank you.

raul77,

the first question I have for you.
is the plc input type and the photocell type compatible?

what I mean is the photocell output a sourcing output or a sinking input?
is the plc input a sinking or sourcing input?

since you didn't give the plc type, this is the first question to answer. the two devices must be compatible.

regards,
james

NPN sensors are current sinking devices and PNP sensors are current sourcing devices. You can't connect a current sourcing sensor to another current sourcing input. It just won't work unless you provide a path to ground. Also a current sinking sensor must be connected to a current sourcing input. So you have to know something about the input circuitry of the device you're trying to sense things with.

Sensor is NPN. It's clear that PLC input is PNP.
raul77 - Can you order a PNP version of the sensor?
If not, then you need a pullup resistor to make NPN sensors work with PNP inputs.
Add a 2.4K resistor from 24DC to the PLC input.
2.4K will give you 10 mA. That should be enough, with a little room to spare.

love it when somebody remembers the old logic days of pull up and pull down resistors