I'm assembling my own power supply, which pin on the connector is positive?

Barrel Plug: The on board DC power connector requires a 2.1mm mating connector. Complete dimensions of the mating plug on the power supply we use are: 5.5mm (outside) x 2.1mm (inside) x 9.5mm (length).

Polarity: The CENTER pin is positive.

It's very important to get the polarity correct if you are assembling your own power source and it's recommended you use the following proceedure to test your work.

1. Assemble your power supply BEFORE insering the IC or soldering in the LCD display.
2. With the LCD screen and the IC not in the PCB, connect your power supply and power on the board. Check for correct polarity and proper voltages. C4 is a good spot to check for +5V, pin 1 (square) is positive and pin 2 (round) is negative.
3. Once you are sure the power supply is wired correctly, you can proceed to adding in the LCD screen and 23017 port expander.

If you have any questions feel free to contact us.