NPN output sensor

[bigjoe 0]

Hi, I have an omron reflective sensor and I want to use it with my mitsu FX0 plc. I am not sure how to connect it or it might damage the plc. The sensor terminals goes like this: brown wirel------------------+24V black wirel----[load]----l blue wirel-------------------0V The load base from the configuration, should be connected between the black and brown wire and when the light is out there is a +24V between those wire. comments? suggestions? thanks in advance johnny

[panic mode 246]

keep the sensor power (brown to +24 and blue to 0vdc). connect black wire (sensor output) to plc input (if the inputs are DC of course). connect SS terminal for that group of inputs to +24 (this is the "other" side of the "load"). this whole group of inputs will now require NPN inputs (if i recall correctly all inputs on FX0S are in one group / have same common). to connect PNP sensor, everything is same except the SS (sink/source select) is connected to 0vdc. to connect mix of PNP and NPN sensors, either separate groups are needed (usually separate card if supported by plc model) or you have to use some circuit to invert the polarity (relay, SSR or whatever). for inputs it is usually ok to simply add pull up or pull down resistor (depending on polarity) to achive similar effect but the signal will be inverted ("normally closed"). --- edit ---- see FX0S hardware manual dc input wiring is in section 5.1

[bigjoe 0]

thanks panic the fxo terminal: input com x1 x2...........x13 output +24 com com0 Y0 com1 Y1........com4 Y4 Y5 Y6 Y7 What if I will use the +24 V on the output side to power up the sensor and the black wire to one of the input side e.g. X1. Is that correct then? or it will do harm or something strange will happen? regards, johnny

[panic mode 246]

some plcs like FX series have built in 24VDC power supply. you can use it just like any standard power supply but be carefull with current draw since they are very limited. this is provided only as an option to power sensors (not the loads). it can be handy for testing things out on the bench but it is good idea to avoid this - unless you are sure not to cry if you accidentally burn it and your plc is suddenly not working.

[Goody 5]

Actually the 24V dc onboard supply on the FX models is very good and robust. If you overload it, it just shuts down. If you short circuit it - it just shuts down. I had an FXoN that was short circuited for 3 days. The run light kept flicking on and off - when I discovered and removed the short - the thing powered up with no problems.