Created Feb. 25, 2019, 8:37 a.m. by Paulson M
The optical distance switches, WORLD-BEAM QS18 Series, are used on the main arm to help determine its exact position. The sensors operate at 12VDC (or more) which is above the 5VDC max the RoboRio's DIO pins can take. Two sets of four optocouplers are used to take the 12VDC from the sensor's and turn it into a pull-to-ground on the RoboRio's DIO pins. The RoboRio's DIO pins are normally pulled high by an internal, high value resistor to 3.3VDC.
In the image below the two four-way optocouplers are visible in the middle above the PDP attached to a bit of lexan. The boards are green with the green screw terminals being most prominent in the photo.
In the image below four of the WORLD-BEAM QS18 Series sensors are shown attached to a half-moon piece of lexan. The limit switches have not been installed in the photo.