On Sat, 15 Nov 2008 08:21:41 -0500, Carl Boyd wrote:
"Karl Townsend" ... wrote ...
I'm about to purchase a photo eye. http://tinyurl.com/6bjmeb

What's the difference between PNP and NPN? I just want an eye that's NC
powered by 12VDC that uses very little power.
....
It has to do with the output transistor construction. From a practical
point of view, if your load has to be grounded get the PNP, if the load
has to be tied to the power supply, get the NPN.

That's as shown in the data sheet from data sheets page,
http://web1.automationdirect.com/sta..._12mmphoto.pdf
http://web1.automationdirect.com/sta...s/sensors.html

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jiw