VISUAL COMPASS

The first test circuit is about the simplest circuit that can be designed around the device. The sensor is drawn in the schematic as if you are looking through the top of the sensor to the 12 leads below. The circuit uses four LED's for display. Each cardinal position on the compass lights one LED. The intermediate directions light two LED's .
Notice that all the number 2 ground leads are tied together. As are the number 1 leads connected to +5 volts Vcc. The sensor will operate supply voltages from 5 to 18 volts. I used a 7805 to regulate the 9V battery to a constant 5 volts. The LED's used in the circuit are red micro-miniature type that operate using little current. The 1K resistors limit the current flowing through the LED's to about 5 mA.

The sensor is dampened to approximate the speed of a liquid filled compass. The dampening prevents over swinging the direction. In addition the built in hysteresis prevents flutter when near a switching direction. The 1490 device is sensitive to tilt. Any tilt greater than 12 degrees will create directional errors.

Testing & Calibration
To calibrate the compass you will need to use a standard magnetic compass. Find north with the standard compass. Rotate the prototype assembly so that just one LED is lit. Use that lit LED as north. If the wiring of the sensor matches the schematic the other 3 arrays will automatically fall in proper sequence. I used the LED furthest away from the sensor for north. The digital compass does not have a definitive magnetic north reading (position). You can make magnetic north any one of the LED readings . Turning the compass in a clockwise direction will cause the LEDs to light, following the sequence .