issue with homemade DC motor + hall effect sensor

[Soremade]

Hi everyone,

I'm building a brushless DC motor for my students but I have an issue.

The tutorial I followed :

I recorded the issue right here :

We can see that the motor does not rotates entirely. I suppose the hall effect sensor does not send the order at the right moment but I don't know how to solve it. Any idea ? I'm quite frustrated cause I feel close to the goal.

The circuit I did is attached bellow.

Thanks a lot in advance,
Guillaume

 

[Alec_t]

Have you tried re-positioning the Hall sensor?

 

[bertus]

Could there be a problem with the mosfet.
It has a gate voltage threshold of 2 to 4 volts.
An irlz44 has a threshold voltage of 1 to 2 volts.

Bertus

 

[Alec_t]

Could there be a problem with the mosfet.

I wondered about that, particularly as the circuit has no back-emf spike protection for when the coil current switches off. However, the power supply in the video shows switching between 0 and ~140mA, so presumably the FET is doing its stuff.

 

[Soremade]

Thanks Alec, yes I've tried many different position with the sensor.
Unfortunately Bertus I won't be able to check that point before next week but thanks for your suggestion.

 

[bertus]

Is the orientation of the magnets (north / south) correct?
Is the polarity of the coils correct (is one of the coils the wrong way around)?
Did you try to hold the hallsensor the other way around?

Bertus

 

[Soremade]

Hi everyone,

Thanks again for helping.
I tried repositioning the sensor in all the the ways but the one in the video is the one that works the best.
I suppose that the magnets orientation and coils polarity is good since when the coils are turned on, the magnet always return to the same position.
I checked the voltage going out of the sensor, it's 2,2V so it should work well with the mosfet.

Any other idea ?

 

[bertus]

Hello,

With 2.2 volts there is a possibility that the mosfet will not turn on, as the gate threshold is between 2 and 4 volts for the irzf44.
An irlz44 will likely have more success.

Bertus