Does a Breadboard Compatible DC Barrel Jack Have to be Connected to Positive and Ground to Receive Power from an Outlet?
Below is a basic schematic of how everything will be connected. V1 is the Arduino power supply, either 5V usb, or 7V to 12V dc barrel jack. V2 is the Lock Strike power supply. It will vary based on your lock strike, probably 12V to 24V. Regardless of the combination, the red wire below connects the grounds of both power supplies together (the DC, barrel jack side, not the AC wall side!). Just connect any ground connection on the Arduino to the emitter of the TIP31/ground of the lock strike power supply.







simulate this circuit &ndash; Schematic created using CircuitLab