Simplifying Motion Detection and Measurement for Automotive Control Systems
By Charles Kuo, Hall Sensor Product Line Manager
Today’s cars are highly complicated and contain an ever-increasing number of gadgets, features, and electronic systems. Automotive designers must make sure this doesn’t become overwhelming for drivers and passengers and need to provide reliable, ergonomic, and easy-to-use controls.
Traditionally, many in-car controllers would have used components that require physical contact, such as potentiometers. However, these contact-based devices wear out over time and become less accurate.
Instead, contactless sensors can provide a precise, reliable solution that doesn’t deteriorate with long-term use. In-car devices that can benefit from contactless sensors include rotary and push selectors on infotainment systems, stalk gear shifters, door handles and locks, and powered seat adjusters.
Why Hall Sensors?
Hall effect sensors can provide the accuracy and reliability needed for these automotive applications.
Discovered by Edwin Hall in 1879, the Hall effect describes how a voltage is produced across a conductor that is carrying an electric current when it is in the presence of a magnetic field. By measuring the voltage, the distance of the magnet from the conductor can be determined.
In a motion controller, such as a joystick, the magnetic field is typically provided by one or more permanent magnets, mounted on the moving part of the joystick. The Hall effect sensor is usually mounted in the part of the controller that does not move, and it measures the change in magnetic field due to the magnet’s movements.
Accurate 3D Sensing
An example of an automotive 3D magnetic linear Hall sensor is the AH4930Q from Diodes Incorporated. This provides high-accuracy 12-bit data with resolution down to 1 Gauss, with an on-chip temperature sensor providing accurate compensation.
The sensor has a robust signal path and a high-resolution ADC, which enables precise measurement of magnetic fields in all three axes. This allows accurate decoding of three-dimensional linear and rotation motion and position information. Its I2C interface provides straightforward, flexible communications with a microcontroller, with data rates up to 1Mbps.
For reliable operation in harsh automotive environments, the AH4930Q has been qualified to AEC-Q100 Grade 1. It has an extended temperature range of -40°C to +125°C. For industrial applications, Diodes also provides the AH4930 commercial-grade version of the sensor.
The sensor has three operating modes and variable update rates, with a power-down mode that has current consumption of just 9nA. During operation, typical power consumption when sampling at 10Hz, is very low at 13µA. A fast-sampling mode (3.3kHz) still only consumes 3.8mA, providing efficient sensing of even the most dynamic and rapidly changing controllers.
Hall sensors, such as the AH4930Q, provide a high-accuracy solution for automotive proximity, push, and rotary motion sensing applications. Their contactless operation offers excellent long-term reliability, and they are straightforward to integrate with a host system – ensuring drivers and passengers can stay in control of all the features in their vehicles.
Automotive-compliant - AEC qualified, manufactured in sites certified to IATF 16949 and supporting PPAP documentation.
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