HMC5843 3-Axis Electronic Compass

Welcome to the training module on HMC5843 3-Axis Electronic Compass.
This training module will introduce HMC5843 3-Axis electronic compass solution.
The earth's magnetic field is about 0.6 gauss in an open-air environment, and has a direction from the magnetic south pole to the magnetic north pole. This pointing to the north pole is the basis for magnetic compassing. At the equator, the magnetic field direction is entirely a horizontal vector, but as you compass further into the northern or southern hemispheres the magnetic field will point partially downwards (northern hemisphere) or upwards (southern hemisphere). This angle down or up at the earth's surface is called the inclination (dip) angle. The high compassing solutions benefit for personal, vehicle, aircraft, and marine navigation. Honeywell offers two-axis magnetic compass and three-axis magnetic compass solutions. The two-axis solution measures the horizontal vector components of the earth's magnetic field using two sensor elements in the horizontal plane but orthogonal to each other. The three-axis magnetic compasses contain magnetic sensors in all three orthogonal vectors of an electronic compass assembly to capture the horizontal and vertical components of the earth's magnetic field.
The Honeywell HMC5843 is a surface mount multi-chip module designed for low field magnetic sensing with a digital interface for applications such as low cost compassing and magnetometry. The HMC5843 includes 1043 series magneto-resistive sensors plus Honeywell developed ASIC containing amplification, strap drivers, offset cancellation, 12-bit ADC and an I 2 C serial bus interface. The device can be operated in three mode, sleep, standby and normal operation mode, which makes it suitable for battery powered applications.
The HMC5843 is a highly integrated solution in a small package size, which makes it easy to use, just adding a microcontroller interface and two SMT capacitors. It utilizes Honeywell’s Anisotropic Magneto-resistive (AMR) technology. The sensors feature precision in-axis sensitivity and linearity, solid-state construction with very low cross-axis sensitivity designed to measure both direction and magnitude of Earth’s magnetic fields, from tens of micro-gauss to 6 gauss. The low voltage operations enable it for battery powered applications. Set/Reset and offset strap drivers for degaussing, self test, and offset compensation. The stand QFN package makes it easy to assembly and compatible with high speed SMT assembly.
The HMC5843 is designed to improve accuracy and location readings in consumer electronics applications including mobile phones, personal navigation systems and portable automotive navigation systems. The chip increases functionality in consumer electronics by providing expanded direction awareness when overlaid on GPS-enabled maps, making it easier to read digital maps on handheld devices. It is also suitable for other high volume, cost sensitive applications, like GPS enabled wireless phone and handheld GPS receivers.
Here shows the block diagram of the HMC5843. The magnetoresistive sensor circuit is a trio of sensors and application specific support circuits to measure magnetic fields. With power supply applied, the sensor converts any incident magnetic field in the sensitive axis directions to a differential voltage output. These signals are multiplexed into the amplifier and sent to ADC. Finally, the control logic block controls the system clock, serial bus interface, and measurement modes. The H-Bridge contains large switching FETs capable of delivering a large but brief pulse to the Set / Reset strap of the sensor. The bias current generator is used to apply a bias current to the offset strap of the magneto-resistive sensor, which creates an artificial magnetic field bias on the sensor. An internal voltage regulator, depending on the application needs, may be used instead of supplying voltage to pin DVDD.
The anisotropic magneto-resistive (AMR) sensor is one type that lends itself well to the earth’s field sensing range. AMR sensors can sense DC static fields as well as the strength and direction of the field. This sensor is made of a nickel-iron thin film deposited on a silicon wafer and is patterned as a resistive strip. The properties of the AMR thin film cause it to change resistance by 2-3% in the presence of a magnetic field. Typically, four of these resistors are connected in a Wheatstone bridge configuration shown in the figure so that both magnitude and direction of a field along a single axis can be measured. The reaction of the magneto-resistive effect is very fast and not limited by coils or oscillating frequencies. The key benefit of AMR sensors is they can be bulk manufactured on silicon wafers and mounted in commercial integrated circuit packages. This allows magnetic sensors to be auto-assembled with other circuit and systems components.
Control of the HMC5843 is carried out via the I 2 C bus. This device will be connected to this bus as a slave device under the control of a master device, such as the processor. Here shows the typical connection between HMC5843 and an MCU. This device shall support standard and fast modes, 100kHz and 400kHz respectively, but cannot support the high speed mode (Hs). External pull-up resistors are required to support these standard and fast speed modes. Depending on the application, the internal pull-ups may be used to support slower data speeds than specified by I 2 C standards.
The demonstration board for the 3-axis Compass IC provides the HMC5843 plus serial bus conversion circuits to convert the I2C data to USB interfacing for personal computers. Includes a 6-foot USB cable, software, user manual & 5 samples of the HMC5843.
The HMC5843 evaluation board for the Compass IC contains the HMC5843 atop a 0.8&quot; by 0.8&quot; plug-board with wide-DIP spaced (0.6&quot;) pins for solderless breadboard compatibility. The evaluation board also contains the two capacitors and I 2 C pull up resistors needed for typical function for the retrieval of the XYZ magnetic field information. Both single and dual supply configurations of the HMC5843 are supported
Thank you for taking the time to view this presentation on “ HMC5843 3-Axis Electronic Compass” . If you would like to learn more or go on to purchase some of these devices, you may either click on the part list link right beside the play button on the TechCast portal, or simply call our sales hotline. For more technical information you may either visit the Honeywell site, or if you would prefer to speak to someone live, please call our hotline number, or even use our ‘live chat’ online facility. You may visit element14 e-community to post your questions.

HMC5843 3-Axis Electronic Compass

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