This is my first post thank you for your time.
I would like to read the state of an led on a laser level and have the Arduino with a relay shield control a hydraulic valve on an earth moving machine. My question is what is the best way to tell if an led is on or off on another device. I have the laser receiver open and thought it would simple to solder a wire to the anode side of the led and connect to an analog pin on the Arduino. Then connect the cathode side to the ground on the Arduino then simply read the voltage. The problem that I see is all the leds have a common trace to the anode side and the cathode side is switched. I need to read five leds, level, 0-1 inch down, 1+ inch down, 0-1 inch up and 1+ inch up. Keep in mind I am new to electronics so please speak slowly. I searched google and this forum but the anode common to all leds confuses me.