We have been using the Banner DS18VN6LP photoeyes for a few years now, and absolutely love them, the packaging, the polarized light, the multiple mounting options.
http://www.bannerengineering.com/en-...f/17406#wiring
The DSC and roboRio have pull up resistors, so when nothing is wired, all inputs read TRUE, high value. When you want to get a signal, you need to short the signal pin of the PWM to ground.
On the DSC, these sensors worked find when powered from the 12v PDP, and were NPN so would short the signal to the negative of the battery.
Yesterday we stripped two bots of controls and were testing the sensors pulled off to put back into stock for this year on the roboRio.
We were powering them from the VRM 12V 2A connectors, and all of these Banner sensors tested bad, they would not read changing states on the roboRIO.
We also had some Allen-Bradely units similar to the logomotion line following sensors, but in a different tubular packaging that worked fine.
I fine it really odd that all of the banner sensors tested bad, so I do not have faith in the test.
So now I am thinking maybe the VRM has some circuitry that may isolated the ground being shorted by the sensor?
I did not think to test sensors when powered from a PDP channel.
Any hardware guys can explain what is going on, or what power source I should be used to power the sensors so the RoboRIO can sense the ground state?
Tell the truth - that's really a small barbecue grill on that robot isn't it. - Tom Line [more] 
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