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motor shield to 8 wire unipolar stepper
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motor shield to 8 wire unipolar stepper

by michaelcasselli on Fri Oct 22, 2010 11:44 pm

I am in the middle of working through the motor shield and have an 8 wire unipolar stepper motor. I have identified the a+ a- b+ b- wires 1 is a+ 2 is a+ 3 is a- 4 is a- 5 is b+ 6 is b+ 7 is b- 8 is b- and I am a bit confused as to the hook up sequence to the motor shield. I have been using steppers for a number of things recently and have had to use 4 wires a+ a-, b+ b- to run them, and know that the remaining wires are shorted to each other, but again, am confused as to how to arrange the wires from the motor I have to the shield. Any suggestions?
Michael

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Re: motor shield to 8 wire unipolar stepper

by adafruit_support_bill on Sat Oct 23, 2010 6:12 am

Your motor is likely a bifilar wound motor. It has 4 coils. You want to connect them into two pairs of series windings. This will be equivalent to a '6 wire' unipolar motor. Connect the two center taps together (equivalent to a '5 wire' unipolar), then conect the center taps to the ground terminal on the shield. You will now have 2 pairs of wires corresponding to the 2 sets of series-wound coils. You may need to experiment a bit with the polarity of those until you find a wiring configuration that steps smoothly.

Check the resources page for more info on motor types: http://www.ladyada.net/make/mshield/resources.html

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Re: motor shield to 8 wire unipolar stepper

by michaelcasselli on Sat Oct 23, 2010 11:16 am

When you say the two center taps, how does one identify which are center taps? I have metered for resistance and have those wires which have continuity paired up and the break down I gave previously reflects that. I should also say that each pair reads the same resistance . So, I am assuming a+ a+ is one coil , a- a- is another coil and so on. If this is the case and all pairs exhibit the same resistance and continuity, how does one decipher which wires are center tap? I guess I am in the dark because I have made the connector for the motor, and other times I have been able to look up the pinouts based on wire color, and, I have never dealt with this type of unipolar motor before. Plus I have only dealt with a+a- pairings with two sets of the wires shorted to each other.
Thanks for the help
Michael

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Re: motor shield to 8 wire unipolar stepper

by adafruit_support_bill on Sat Oct 23, 2010 11:49 am

Start with 2 of your coils. When you wire them in series, you get what is effectively one coil with a center tap. The 'center tap' is the pair you twisted together.

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Re: motor shield to 8 wire unipolar stepper

by michaelcasselli on Sat Oct 23, 2010 1:56 pm

Arduwino,
Thanks for the nomenclature, it is what I thought but did not know the language. So, I have the motor jogging back and forth but not spinning. Is this where the polarity changes come into play? I assume that right now the coils are not firing in the correct sequence. Continuity implies the same coil, so is there a way that it can be sorted out easily, or is it a matter of swapping wiring around til it works?
Michael

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Re: motor shield to 8 wire unipolar stepper

by michaelcasselli on Sat Oct 23, 2010 3:10 pm

Well, identified the coils, the center tap, and have tried all possible combinations of polarity and all I get is a back and forth jog of the motor as it goes through all the steps of the sketch. Any thoughts?

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Re: motor shield to 8 wire unipolar stepper

by adafruit_support_bill on Sat Oct 23, 2010 3:41 pm

Im guessing that it is a bifilar wound motor. (see jones: http://www.cs.uiowa.edu/~jones/step/types.html#bifilar)
You will have to try different pairings of the coils too.

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Re: motor shield to 8 wire unipolar stepper

by Train Tester on Tue Feb 18, 2014 3:44 pm

Hi Michael,

I'm trying to connect an 8 wire stepper myself,

Did you have any success?

I'm struggling, I have my coil pairs and my wires are as follows - 1 = black, 2= blue, 3 = yellow, 4 = red, 5 = green, 6 = brown, 7 = purple and 8 = white.

Any chance you could help out?
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