Posting becasue these are very useful sensors and also because I have a question about using them.
I needed a reliable sensor for a limit switch, and found these cool Panasonic sensors: http://pewa.panasonic.com/automation-controls/sensors/proximity-sensors/gx-f_h/
Extensive data sheet here: http://pewa.panasonic.com/assets/acsd/sunx/sensors/catalog/gx-f_h-catalog.pdf
Basically a very small metal detector, with coil and oscillator, that closes a circuit when anything conductive gets near. Can be set very precisely; they are very small, and water/oil proof. Around $30; worth every penny to me. The indicator light on them is super handy for setting up and troubleshooting.
Two questions, I'm NOT an expert in electronics: The one I got hold of is a NPN type, see circuit figure attached. I'm used to open collector PNP sensors; just send the signal wire to an Arduino pin, use external or internal pulldown resistor; look for 5V (HIGH) when on.
But I can't get my head around this one. I connected the signal to a pin; used the internal pullup resistor with code, and looked for LOW, and this worked perfectly. Since I don't really understand transistors, I'm assuming the voltage/current OUT of my digital Arduino pin is enough to pass through the transistor in the sensor. Just the reverse of PNP, right? (And this is "sourcing" v. "sinking," maybe?)
Second, datasheet says this unit needs 12-24V. I have that available in my setup (from stepper driver), but everything seems to work just fine at 5V. We will eventually make a lot of science instruments with this thing, will I be OK with 5V for all of them?
Many thanks! We're developing open source tools for our river models; www.emriver.com .
