The LED circuit is interrupted by a PNP transistor, which is controlled by the output of the hall effect sensor, so that they turn on when the hall effect turns off.

These hall effect sensors require a steady current to work, so they must be independently grounded to allow a small intentional leakage current, therefor the necessary circuits will be power to sensors, power to LEDs, ground from sensors, ground from LEDs, all separately. Again, any will do.īesides some wire bits, that's all you need. (1x) Protoboard, I used a 2x8cm with 2.54mm pitched holes. (1x) Switch, not really necessary, any will do, I had these lever microswitches on hand so I used them. (2x) PNP transistors, I used a 2N3906 because they're cheap and easy. I solved this problem by putting a small red sharpie mark on the bottom of the red LED. Note, if you use clear LEDs like I did, don't mix them up (like I did). (2x) LEDs, pick one for each color, I used red for north, and blue for south.

(4x) 1k Resistors, I used 1/4W 1% metal film resistors, but it doesn't matter much. (2x) Y3144 Hall Effect Sensor, interchangable with A3144, A3141, and a couple others. The parts required are as follows, and visible in the first picture:

2n3906 download