You can add a micro plug to the circuit by just connecting all 4 pins of the micro plug together and then to positive,
Just make sure to plug in one cable at a time or else you won't know which cable is being checked.
The circuit itself is simple, I made it a bit more complicated ( if you want to say that ) by making and putting it in an enclosure,
Just a simple 3d printed box.
Here's the circuit diagram and you can download the box stl. files below
