Wiring a proximity sensor

I'm replacing a Printrboard with a RAMPS 1.4 board. I've become a confused about the wiring for the sensor. The sensor that I'm using is the LJ12A3-4/BY unit. It is a PNP type, with a supply voltage of 6-36V, current output is 300ma. Most of the information that I have been reading talks of a voltage divider, but the sensor used on the Printrboard does not have one. So I'm not sure what to do?

Edited 1 time(s). Last edit at 02/18/2015 10:54AM by kd6hq.

You're going to have a few problems with that. RAMPS operates at 5V, while that sensor wants 6-36. You can use a separate 12V power source, but since it's a PNP the controller will sense when the signal goes high. Your Arduino will quickly release it's magic smoke if you feed a 12V signal into a input pin. That is where the voltage divider comes into play as it will drop the voltage down to 5V if properly wired.

Also if that's a NO sensor that's the opposite of what is preferred. A NC switch will "fail safe" if it becomes unplugged or otherwise non-operational where if the same happens with a NO switch, you won't know.

I think my confusion come from my current sensor plugs into the Printrboard without the voltage divider. So I'm thinking that it is running off of 5V instead of the 12V the voltage divider takes. Looking at the Printrbot web page I see now they added a divider circuit (when needed). They say to try it first then add the circuit if it does not work.
Or I could just go ahead and add the circuit to take the guesswork out of it.
Which leads me to the next question. There is a 12V-AUX-pin set, any reason that could not be used as the source V?

Ok I will search for an NC sensor of the same size, unless you happen to know of one?

thanks

You can steal 12V from the header pins (or holes) next to D2 near the polyfuses, the main power input plug(s), or the + terminals of D8-10 (they are always hot).

Ok, I think I'm going to need something a little simpler if you don't mind.
It's been a very long time since I've looked at anything except a resistor symbol.

On the RAMPS 1.4 board I have "S - +", so what goes to what?

Is it :
Brown goes to "S"
Black to "+"
Blue to "-" ?


I know that I may want to replace this with a NC device and I may have to add the voltage divider. But it's working now at 5V. so I would like to see if it works on the RAMPS board at 5V. first. Otherwise I will order all the parts at once if needed.

thanks

On the board, S is signal, - is negative, + is +5V

So brown goes to +, Blue goes to -, and Black goes to S.

got it thanks, all is well now, up and running.

thanks again