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AnsweredHot!BLDC help

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melvinpmathew
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2020/07/02 07:32:31 (permalink)
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BLDC help

Hi All,
 
Need some help with BLDC operation on MCLV2 and dsPIC33EP512GM706 chipset.
 
I have been trying to implement BLDC for a project, with help of libraries/code for AN1299, was able to rotate the BLDC motor(not hurst motor, got BLDC from ebay). Had to implement a couple of tweaks to the code to make it run with this motor.
 
Now facing issue where the hall sensor f/b signal is not clear. When i manually rotate the motor (couple of rotations) , i get a clean hall value signal :
 
See hal1.jpg attached
 
But on loading the code , and running the motor using PWM signal, i am getting this on HALL f/b:  - (similar number of rotations as done manually)
 
See hal2.jpg attached
 
I was expecting a clean hall f/b - any idea what's going on? Trying to use the HALL f/b for counting the number of rotations done by motor-
 
Also, is there any other code\library which can be used for this?
 
 
post edited by melvinpmathew - 2020/07/02 09:07:07

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#1
du00000001
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Re: BLDC help 2020/07/02 08:54:23 (permalink) ☼ Best Answerby melvinpmathew 2020/07/02 09:07:17
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Try to post your image in a way that doesn't require decoding efforts!

PEBKAC / EBKAC / POBCAK / PICNIC (eventually see en.wikipedia.org)
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melvinpmathew
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Re: BLDC help 2020/07/02 09:08:36 (permalink)
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Corrected the POST with images attached. Thanks @du00000001 for letting me know.
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du00000001
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Re: BLDC help 2020/07/02 09:57:03 (permalink)
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Doesn't look like any Hall signals. Even those in hal1 do not look like regular Hall sensors (channel C is more than creepy).
And the signals in hal2 are crap/useless - or maybe crosstask from PWMs. Or magnetic crosstalk from the windings.
 
Provided you've got a datasheet: could it be the sensors need some low-resistance pullups? I'm somewhat wondering you got the signals in hal1 at all.

PEBKAC / EBKAC / POBCAK / PICNIC (eventually see en.wikipedia.org)
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melvinpmathew
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Re: BLDC help 2020/07/02 10:14:08 (permalink)
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That's what I thought might be leak from the PWM. Hal1 is completely manual rotation - so thought it was looking good - maybe not. 
 
The BLDC doesnt have a proper datasheet - as its an eBay buy. Just basic info. 
 
I think low-res pullpus maybe able to clear the signal.
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du00000001
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Re: BLDC help 2020/07/02 10:22:39 (permalink)
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It really depends on the make of Hall sensor: either you should get a pulse when a magnet pole passes (irrespective of the polarity), or the Hall's outputs should look like the BLDC phase powering scheme (which I tend to call "brick wall"). Hal1 shows something resembling the brick wall (although not without doubt) for channels A and B, but channel C is completely off pattern. And hal2: creepy.
Provided you have the denomination of the motor, you might be lucky to retrieve some datasheet by means of g..gle. Or - just maybe - the vendor is willing to provide the information. Otherwise: good luck with this motor  sad

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melvinpmathew
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Re: BLDC help 2020/07/02 10:30:42 (permalink)
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No wonder microchip support wants me to get a hurst motor for $200 :). Anyways, let me see what to do, thanks for your inputs.
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du00000001
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Re: BLDC help 2020/07/02 10:42:25 (permalink)
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Is the Hurst that much?
Couldn't even remember - bought mine in 2007 - most likely with a considerable discount.
But you're about right.
 
The point is that the Hurst motor has Halls PLUS an optical encoder (which is not exactly cheap) - allowing for virtually any control scheme from BLDC to PMSM/FOC with or without the sensor of your choice. Quite versatile.

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