3D Hall-Effect Sensor for Knobs in Appliances
Abstract
Knobs are widely used in many scenarios as a way for humans to interact with machines. Detecting the rotation angle of the knob is required in most applications. Compared with traditional knobs, knobs using Hall-effect sensors have more advantages. TI 3D linear Hall-effect sensors such as the TMAG5273 and TMAG5170 can measure magnetic fields in three directions, and can calculate angles in any two axes using the on-board CORDIC calculator allowing the MCU to read the angle directly. In addition, a push-button knob design can provide more versatile functions.
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1 Problem with Mechanical Knobs and Rotary Encoders
There are many products in home appliances that use knobs, such as microwave ovens, water dispensers, air fryers, cook-tops and so on. Figure 1-1 showcases just a few examples of knobs on home appliances. At present, there are two mainstream knob designs: mechanical and rotary encoder. Mechanical knobs are bulky and unsightly, and these knobs wear out after long-term use, which affects their service life. The contact based rotary encoder knob is easily disturbed by the environment, such as water and dust. Contact based rotary encoder knobs are not practical in many scenarios. The price of these knobs can also be expensive. This document introduces a knob design based on the 3D Hall-effect sensor which can avoid the shortcomings of the above-mentioned designs. The 3D Hall-effect sensor has the advantages of small size, long life, low cost, and these sensors are not easily disturbed by the environment.
Figure 1-1 Knobs Used in Appliances