Digital Compass-circuit diagram made with UGN3503 Hall device

This paper introduces the design purpose, system structure and working principle of the digital compass designed with two UGN3503 type Hall devices, and how to use the main devices. The system includes UGN3503 type Hall device, TLC0832 A/D converter, SCM control, liquid crystal display four parts, realize the geomagnetic information acquisition, amplification, through the analog-to-digital conversion and SCM processing, the final display of the current position in the text representation.

Now the robot control has a great development, especially the remote control robot, but can not be like people have their own exploration. Basically put on the camera manual control, so to a large extent do not have the ability to work independently, leaving people and GPs still can not work. We developed this system to provide a raw reference for a digital system in a hostile environment, or to act as a cheap measurement and control tool for a robot.

In this purpose, the main functions of the system are:

1, geomagnetic amplification function: through the internal magnet to the ground magnetic field response, to achieve the amplification of geomagnetic information.

2, System-assisted positioning function: Through the equipment provided by the serial port, can not only embed the system, for the system's spatial positioning to provide reference data, but also as a peripheral, to provide temporary measurement.

The output mode of this system can use liquid crystal display and voice output two ways, the voice output can provide convenience for the blind.

The block diagram for the entire system is shown.

We fixed the two vertical hall devices at the bottom of the frame (as shown), and sandwiched a hollow plastic cylinder between the N and s poles of the two small magnet strips so that they would just fit the two hall devices into place without contact. The top of the cylinder is sealed, and a plastic shaft is drawn from the center of the top, fixed at the bottom of the frame, allowing the cylinder to rotate freely around the central axis.

In this way, the small magnetic stripe can be used to indicate the direction of the Earth's magnetic field, because the magnetic field between the two magnets is much stronger than the Earth's magnetic field, so the hall device can detect the changes in the surrounding magnetic field, so as to achieve the amplification of geomagnetic signals.

As shown in the picture on the right, hall device a detects a magnetic field in the X direction and B detects a magnetic field in the Y direction. At some point the direction of the magnetic field is as shown on the right, and the magnetic field detected by A and B is a and b respectively. Then the single-chip microcomputer can obtain the value of azimuth θ by processing the two data, thus determining the current orientation. The direction of the dashed arrow in the right image is the direction of the magnetic field, that is, the direction of the x-axis, which is the direction of the observer.

There are a variety of hall devices on the market, but most of the sensitivity is low, considering the magnetic induction magnetic field is weak, we carefully selected the UGN3503 type Hall device. This Hall device has a high sensitivity and low noise output. As the information collected by this device is a continuous change of the analog volume, can not be directly processed by the machine, the analog must be converted to a digital amount before it can be input to the microcontroller for processing, so we chose A/D converter TLC 0832. The TLC0832 is a 8-pin, 2-channel A/D converter for serial communication and has advantages in both function and volume. We can also change the 51 to 2051 to further reduce the volume. and serial communication can make it with 3503, so that data transmission is not limited by distance. This converter is compatible with the processor interface and can operate on a single machine. Under 5V voltage supply, the voltage within the 0~5v range can be entered. TLC0831 has a single input channel; TLC0832 already has multiple input channels. The continuous output is configured to the interface standard change register or microprocessor. LCD LCD display using LCD1602. This LCD module is 2 lines of output, 16 characters per line.

The entire system circuit diagram is shown.

Considering that the magnetic field may produce unstable conditions at a certain time or position due to external jitter in practical application, we have adopted a design method to take its smooth transition data in several data inter-segment points when we data processing. The MCU finally selects the processing result output mode through the jumper. The System program flowchart is shown.

At present, most devices do not have a simple direction recognition function. For more complex, higher-grade equipment, the use of positioning equipment is stronger, generally not easy to other equipment compatible, and the design structure is more complex, high cost. We design a small orientation positioner that can meet a number of small, directional accuracy requirements of the equipment is not high. Because of the low cost of the development of the equipment, the device can be used in some simple equipment, and it will add a more significant function to the equipment under the condition of small cost increase, and improve its cost-performance.

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Digital Compass-circuit diagram made with UGN3503 Hall device