Line Sensors

[jee7s]

Originally Posted by jtdowney

We found that since the two signal wires (white and black) are just logically oposite that only wiring one was required.

True, this will work to detect light and dark. But, remember there are three states: light, dark, and fault. For example, how would you tell between "logical high" and "the sensor isn't working"...they both would give you +V on the DIO pin.

Originally Posted by Al Skierkiewicz

...I am thinking that the DSC is not receiving power from the PD. When the DSC is connected to the Crio module, but +12v is not applied from the PD, some of the power LEDs do come on through leakage in the module. They do not, however, provide a pullup voltage for digital inputs. The first indication of a problem here is the failure of the robot signal light.

I'd say Al's on the money here. The DSC is deceptive, as it will light up when you plug it into the cRIO, but it's not fully functional. Make sure you're attached to the power distribution board via the DSC's wago connector, and check the +6V light on the DSC. If it isn't lit, you don't have pullup.

Also, I'd suspect that 0.4-0.7V observation was an artifact of the internals of the ADC and the NPN transistor that's driving the light sensor signal line.