This circuit is design circuit to build a digital compass that displays both the direction and cardinal points on a television. Other functionalities were added to complement the sensor interface, such as, temperature display, magnetic declination input and disability option. This is the figure of the circuit;
The HMC1052 two-axis magnetic sensor contains two Anisotropic Magneto-Resistive (AMR) sensor elements in a singleMSOP-10 package. Each element is a full wheat stone bridge sensor that varies the resistance of the bridge magneto resistors in proportion to the vector magnetic field component on its sensitive axis. The two bridges on the HMC1052 are orientated orthogonal to each other so that a two-dimensional representation of an magnetic field can be measured. The bridges have a common positive bridge power supply connection (Vb); and with all the bridge ground connections tied together, form the complete two-axis magnetic sensor. Each bridge has about an 1100-ohm load resistance, so each bridge will draw several milli-amperes of current from typical digital power supplies. The bridge output pins will present a differential output voltage in proportion to the exposed magnetic field strength and the amount of voltage supply across the bridge. Because the total earth’s magnetic field strength this very small (~0.6 gauss), each bridge’s vector component of the earth’s field will even be smaller and yield only a couple milli-volts with nominal bridge supply values. An instrumentation amplifier circuit; to interface with the differential bridge outputs, and to amplify the sensor signal by hundreds of times, will then follow each bridge voltage output.
