Did you know that there are two types of Hall Effect Sensors; latching and non-latching?
Boy, when you think you have a non-latching hall effect sensor and you actually have a latching one it is really hard to figure out what the heck you did wrong.
I created the simple circuit below out of frustration and quickly learned that I had purchased the wrong sensor.
The difference between latching and non-latching is that when you move the north pole of a magnet near a latching hall effect sensor it will switch to HIGH, completing the below circuit, and lighting the LED. The switch will remain set to HIGH and the LED will remain on until you move the south pole of the magnet near the sensor, it will then switch to LOW turning the LED off.
From what I understand, a non-latching circuit will switch to HIGH when the north pole of a magnet is near. When the magnet is moved away from the circuit it will switch to LOW. (Can you picture a mailbox door opening and moving the magnet away from the Arduino in the mailbox???) Time to go shopping!
Use a Hall Effect Sensor and a magnet to complete the circuit and light the LED