### Author Topic: Best way to electronically trigger a Hall effect latch sensor ?  (Read 241 times)

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#### guix

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##### Best way to electronically trigger a Hall effect latch sensor ?
« on: May 27, 2024, 12:48:23 pm »
Hello!

I'm (still) working on a device that is a small test-bench for a moped's digital dashboard. It can test almost all functionalities of the dashboard. Almost all

On the front wheel of the moped, there is a multi-poles ring magnet, and a Hall effect latch sensor (A1220 datasheet), to calculate speed.

Similar to this illustration :

There is 16 pulses per revolution of the ring magnet, and let's say the top speed of the moped is 200 km/h (the dashboard's LCD display will show max 199 km/h). The wheel circumference is ~1800mm, and 200km/h = ~56 m/s, so at this speed, the wheel spins at 56 / 1.8 = ~31 revolutions per second, and the hall sensor is triggered on and off, at a frequency of 31 * 16 = ~500 Hz.

So I would like to have a device that is able to generate a magnetic field that can be detected by the Hall sensor (which will be inside the test-bench enclosure), at a frequency between 0 and 500 Hz that can be set by an arduino program (which I can make). I don't want to get rid of the Hall sensor and simulate the speed directly by an arduino, because the purpose of the test-bench is to test the circuit of the dashboard : if the speed is not displayed on the LCD, then I know there is a faulty component on the PCB of the dashboard.

Of course the first idea I have, is to "simply" replace the wheel of the moped, by a motor with a variable speed between 0 to 31+ revolutions per second (~2000 RPM), and attach a ring magnet with 16 pulses per revolution to it, and control the speed of the motor with the arduino.

But I would prefer if it was silent, with no moving parts, and as small as possible. Is there a better way ? I've searched about using a coil or electromagnet but I'm not sure if it's applicable in my case.

How would you do that, if you were me ?
« Last Edit: May 27, 2024, 12:56:07 pm by guix »

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##### Re: Best way to electronically trigger a Hall effect latch sensor ?
« Reply #1 on: May 27, 2024, 01:03:08 pm »
coil of wire driven by an H bridge,the H bridge reverses the polarity across the coil so the magnetic field polarity changes.

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#### voltsandjolts

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##### Re: Best way to electronically trigger a Hall effect latch sensor ?
« Reply #2 on: May 27, 2024, 01:11:10 pm »
On the front wheel of the moped, there is a multi-poles ring magnet

Well, you need to generate a magnetic field for your test bench, where the magnetic field strength is a little lower than the expected field strength the sensor will see in the application. You could do this by spinning one of your wheel magnets, at a spacing which is just slightly more than the application, to guarantee the sensor works with the minimum expected field strength. Or you could simulate that with a coil as per above suggestion - but make sure the field strength is comparable, or the test doesn't mean much. Using a coil would make it easier to test over a range of field strengths.

Smf