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[SOLVED] How to pulse a three coil stepper motor?

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JohnJohn20

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Hi. I have salvaged a three coil stepper motor and am a bit confused about how to pulse the coils to make it move. Here is a cross section image of the motor:

It has 32 magnets on the rotor around 48 coil stator. These coils are connected in three groups (A, B and C) of 16 coils each. The three groups are joined like a three phase motor. E.g. If I connect positive to the A winding and negative in the B winding, the A coils become North on the outside and the B coils become South on the outside.

In the image, the motor is stationary and A coils are lining up with the north poles of the rotor.

So, how to pulse the coils to make the rotor rotate clockwise?

If I pulse A coils South and B coils North, the rotor will rotate 0.9375°.

Perhaps if I make B south and C north, it will rotate 2.8125°.

Not sure. Any guidance would be appreciated. I would just jump in and play around but this uses about 300VDC and potential high currents.

The motor also has three hall sensors placed between the stator coils. It doesn't look like they are in the center. Not sure how they are used to determine the rotor position to set which couils need to be energised.

Cheers.
 
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Hi,

From the picture it seems:

A+ | B- | C+ | A- | B+ | C - | A+ | B- | C+ |....

Klaus
 

From the picture it seems:

A+ | B- | C+ | A- | B+ | C - | A+ | B- | C+ |....
Hi Klaus. Not sure what you mean.

This is a three wire motor so at least two, possibly three, of the coils must have current going through them. Can't just energise 1.
 

Hi,

First you said three coil, so I assumed you have two wires per coil.

But in the end it means the same.
You may drive it with 3 phase sine. Like mains. Each sine is shifted 120°

Or you have just a DC voltage and power only two of the three wires. Then take two values of my list above.
A+, B- | B-, C+ | C+, A- | A-, B+ | B+, C- | C-, A+......

Klaus
 

The motor also has three hall sensors placed between the stator coils.
This kind of motors is usually designated brushless DC rather than stepper motor and operated with direct feedback between hall sensors and coil drivers. Speed regulation by supply voltage variation.

Other modes of operation are of course possible. Driving it with three 120° phase shifted square waves is an easy one. If variable speed or at least soft start is intended, you need to go for PWM.
 
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