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Measuring RPM intercepting Hall sensors of BLDC motor

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DEPL_PR24
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Joined: 2024-03-14 22:09
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Measuring RPM intercepting Hall sensors of BLDC motor

Hi everyone,

 

Im currently working with a BLDC motor with 3 hall sensors, and using the driver FSESC 4.12, and I want to measure RPM using a microcontroller intercepting the 3 signals of the Hall sensors. I have the 5 cables (power, ground, 3 Hall sensors) connected to a protoboard, and form there its connected to the driver like normally, and to the microcontroller with pull-up resistors.

When I dont turn the motor ON, and spin manually the rotor, I can read the signals of the sensors correctly and measure RPM, but when I turn ON the motor, even when I brake the motor by hand (not rotating but sending manipulation), the signals of the Hall sensors are activating, Ive checked it with an oscilloscope and the signal of the sensors looks like an square changing signal (like if its rotating).

I want to know if there is an specific configuration of the driver to just read the state of the sensors and not to manipulate them, or Im missing something to consider.

I would be grateful for any help....greetings.

 

 

flez1966
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Last seen: 4 months 2 weeks ago
Joined: 2024-03-16 14:49
Posts: 7

the hall lines will be picking up the phase current. 
when the thing is 'off' and you spin by hand you will see the hall line toggle from ground to 5v, when the motor is on and spinning, you will see it toggle between ground and a pwm signal which is lots of fast toggles from the induced voltages into the hall lines. you will need to use some software trickery to filter that out.
 

 

flez1966