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DIY focuser w/o Motor HAT or PiFace?

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Replied by Maurizio Baldassarre on topic DIY focuser w/o Motor HAT or PiFace?

It's not a 28BYJ-48 (unipolar), but a Nema 17 (bipolar). I don't think the a4988 can drive unipolar motors, so I purchased this one for testing. The motor does not vibrate nor gets warm. Looks like no current is flowing at all. Maybe Vref is too low. The voltage on the motor pins on the driver board rises to 4.6 V while I'm sending commands. Starting to think it's a matter of current.
6 years 7 months ago #19190

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Replied by Helge on topic DIY focuser w/o Motor HAT or PiFace?

Are you sure it is a 5v stepper, and not 12v?
6 years 7 months ago #19191

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Replied by Maurizio Baldassarre on topic DIY focuser w/o Motor HAT or PiFace?

On the Amazon page it says "nominal voltage: 3.45 V, nominal current: 1.5A (monophase)".
6 years 7 months ago #19192

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Replied by Helge on topic DIY focuser w/o Motor HAT or PiFace?

Ok. But 1.5A exceeds the 1A the a4988 is designed for. In any case you would need to check the Vref pin - but pls check the pololu Instructions first...
6 years 7 months ago #19193

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Replied by Helge on topic DIY focuser w/o Motor HAT or PiFace?

Here is a link:

reprap.org/wiki/Pololu_stepper_driver_board
6 years 7 months ago #19194

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Replied by Helge on topic DIY focuser w/o Motor HAT or PiFace?

Forgot to mention, there are loads of instructions on YouTube on how to convert the 28byj48 into a bipolar stepper - it is actually fairly easy to do.

Best, Helge
6 years 7 months ago #19195

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Replied by Maurizio Baldassarre on topic DIY focuser w/o Motor HAT or PiFace?

I DID IT!!!! I took the risk and increased the voltage to 12 V, and not it works! I have no idea why it says 3.45V on Amazon, must be a typo!!
6 years 7 months ago #19196

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Replied by Helge on topic DIY focuser w/o Motor HAT or PiFace?

Fantastic, well done! - then current will presumably be lower than the 1.5A. Can you check what current is drawn?

I was also running a 5v stepper at 12v. Unless it is getting warm, should be ok - but I am not an electrician (=disclaimer).
6 years 7 months ago #19197

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Replied by Radek Kaczorek on topic DIY focuser w/o Motor HAT or PiFace?

That's what I thought after I saw your pictures ;-)
I'm glad you got it working!
6 years 7 months ago #19198

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Replied by Maurizio Baldassarre on topic DIY focuser w/o Motor HAT or PiFace?

Is there a way to have INDI calculate the necessary number of steps for backlash compensation? Or should I determine it by hand?
6 years 7 months ago #19250

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Replied by Radek Kaczorek on topic DIY focuser w/o Motor HAT or PiFace?

The driver does not calculate backlash value. You need to determine it manually
6 years 7 months ago #19252

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Replied by Maurizio Baldassarre on topic DIY focuser w/o Motor HAT or PiFace?

Any tips on what would be the best way to determine the number of backlash steps?
6 years 7 months ago #19301

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