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[on:]

I'd like to hook up a DEI 508D Field Proximity Sensor to an Arduino.

It's a 12V circuit, it has two outputs which I'd like to sense.

The green wire is "First stage (-) 200mA output (500mS)"
The blue wire is the "Second stage (-) 200mA output (1S)"

How would I go about sensing this using an Arduino?

This is the "manual": http://www.directeddealers.com/manuals/ig/accessories/2508111_508d_installation_guide.pdf

[Reply #1 on:]

Hmm, rather unclear that document (and my neck now aches

I think it might mean the outputs are open-collector capable of 200mA sink.  However I'd suggest it would be best to measure.

Measure the output voltages with nothing connected, and then again with 10k resistor from output to 5V.  If only the latter works and gives 0..5 range, then open collector it is.  If both generate an output then take note of the voltages involved.  If 12V you'd need a level shifting circuit such as resistor divider.

[Reply #2 on:]

Without a resistor, it measures 0V when inactive, about 6.7mV when triggered.

With a 10K resistor connected between the output and the 16V rail (sorry, no 5V available right now), it reads 15V at the output when inactive, but drops to zero when triggered.

That means it's grounding, right?  How would I sense that, and is it OK to connect that resistor directly to the Arduino's 5V power even though this runs on car 12V?

Thanks for your help!

[Reply #3 on:]

Yup, run a 10k resistor or so from the output to +5V and it'll become a nice 5V logic signal.  Open-collector (or open-drain, same thing) outputs are nice and flexible like this (you can wire several of them together to one pull-up resistor to make a hard-wired AND gate too

[Reply #4 on:]

Great, thanks so much for your help!  I took a few electronics courses back in college, but have forgotten most of it.  Now I'm starting to see what the term "pull-up resistor" actually means!

Again, thanks!