Stepgen and 4-phase steppers

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25 Aug 2020 17:36 #179424 by tommylight
You are welcomed, i was waiting for the bad news ! :)
4 wire motor will most probably not work with the L298, as that means it is a "star" connected motor, for the L298 you would need a "delta" wired motor. That can easily be changed if you have access to the winding leads.

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25 Aug 2020 17:43 #179427 by Skec
Replied by Skec on topic Stepgen and 4-phase steppers
:)

The BLDC motor I have, has 3 single wires, and a spot (named COM), where all those wires is connected to one place..

Between A1 and A2 there is 4.4 Ohms.
Between A2 and A3 there is 3.5 Ohms
Between A1 and A3 there is 4.4 Ohms
Between A1 A2 A3 and COM there is 4.5 Ohms..

If that helps..

I have access to winding leads :)

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25 Aug 2020 19:16 #179433 by Skec
Replied by Skec on topic Stepgen and 4-phase steppers
This is the information (somewhat contradictory) I found so far:

1. In this youtube video its clearly seen that BLDC motor is controlled with 1 x L298N:



2. In yet another youtube video (comment section) it says that to run BLDC you need 2 x L298N:



the reason that we cannot drive BLDC with 1 L298N is "The reason for that is the logic inside the chip - both halves of one full H-bridge are linked in opposite phases - it's either 1-0 or 0-1, which will not work for BLDC motor".

In case it is not possible to control BLDC with 1 L298N and linuxcnc, it would be interesting to rewind the motor to 4 phase (or smth that works)..

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25 Aug 2020 19:40 #179436 by tommylight
From the datasheet it sure looks like it will not work as it can not have both sides of one bridge on at the same time.
I can not recall where they are but i am pretty sure i have 2 or more of those L298 boards around here, that would be easy enough to test.

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25 Aug 2020 19:59 #179439 by tommylight

Skec wrote: ...... it would be interesting to rewind the motor to 4 phase (or smth that works)..

That can not be done, the magnetic poles are made for 3 phase.

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25 Aug 2020 21:57 - 25 Aug 2020 22:09 #179456 by Skec
Replied by Skec on topic Stepgen and 4-phase steppers
I have dissasembled the motor into pieces in order to re solder wires from star to delta. I did not rewind anything, just unsoldered all 3 wires from the com and joined each end to appripriate other end... say we have 3 wires with two ends a a, b b and c c. So I connected a to b, b to c, and c to a. This way I believe (does not mean its true) my motor became delta. With that beying said, nothing changed (does not spin). It still vibrates in one position as if would hold the position...

I guess next step would be trying to rewind the motor (edit: I checked, star and delta windings are the same).. It is certainly not the easy way, but at least now I see what knowledge gaps I made in university... damn

That concludes my journey :/ My only question remains, how that dude from youtube managed to control bldc with one L298n when it is not possible.. fake? Or Magic?
Last edit: 25 Aug 2020 22:09 by Skec.

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26 Aug 2020 12:08 #179529 by tommylight

Skec wrote: That concludes my journey :/ My only question remains, how that dude from youtube managed to control bldc with one L298n when it is not possible.. fake? Or Magic?

No comment on that for the time being, i am pressed for time so i can not test that.
In the mean time, get 3 resistors of 100 to 470 ohm and 3 darlington transistors, set the motor to star windings.

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