I am currently developing some basic led board using Arduino Uno R3. Basically, the LEDs are connected in parallel so that 5V DC supply can light up about 3 LED. Each LED has its resistor and its connected to 3 Arduino digital pin where I ground it by using digitalWrite(pins, LOW). Each ground on the schematic is the Arduino digitalWrite(LOW). My question is where should the negative of the 5V should be connected?
Also, if I wanted to measure the voltage of the LED, where should I connect my probe so that analogRead() can read the voltage?
Thanks and sorry if my explanation is not correct since it's my first time using this site.