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### Topic: 4 Phase Stepper (Read 2102 times)previous topic - next topic

#### imagiro1

##### May 08, 2012, 04:57 am
I am working on a project for a kids museum and get to learn about stepper motors. I have taken a 4 phase 6 wire unipolar stepper motor from an old printer.
http://www.mitsumi.co.jp/latest/Catalog/pdf/motor_m35sp_9_e.pdf

I was trying to use the L293D to control it. Mainly cause I ordered the chip it thinking the stepper was bipolar. I found this drawing for a 6 wire unipolar stepper...
http://www.me.umn.edu/courses/me2011/arduino/technotes/stepper/coilconfig.html

Is it possible to short the two center taps and use the bipolar stepper two-wire circuit as shown in this link?
http://www.tigoe.com/pcomp/code/circuits/motors/stepper-motors/
Are all 6 wire stepper motors wired the same way?

And to figure out which wire belongs to which coil, I will have to a "short" test to find out which set of 3 wires belong to each coil? Then the resistance between the coil ends should be half of the resistance between the end and the center tap?

#### dc42

#1
##### May 08, 2012, 10:29 amLast Edit: May 08, 2012, 10:31 am by dc42 Reason: 1
I believe you have answered your own question correctly in each case.

If you want to use the L293D to control it, ignore the centre tap connections and treat it as a bipolar stepper - but it will need a higher voltage used that way.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

#### imagiro1

#2
##### May 08, 2012, 02:50 pm
Thanks. I was wrong on one though. The center tap should be left alone and not connected to ground.

#### kf2qd

#3
##### May 08, 2012, 08:01 pm
Could build your own driver -

http://arduino.cc/forum/index.php/topic,84809.0.html

I did it using an ATtiny2313 and 4 - IRF89N60A fets. makes a driver that has a step and a direction input and drives the 4 phases of a unipolar motor. Could use other driver transistors. Would make it easy for 1 arduino to control a number of motors.

#### imagiro1

#4
##### May 09, 2012, 03:27 am
I had already ordered the chip. Which came in today and I've wired it up. I seem to be experiencing some odd behavior. I've uploaded the video.
http://goo.gl/GYLTr

I'm using the schematics and code from Tom Igoe's page. I used the L293 bipolar circuit. The center taps are left floating.
http://www.tigoe.com/pcomp/code/circuits/motors/stepper-motors/

You can see the motor looks like it's stepping 3 clicks forward and then one back. I've made the speed slower and painted one of the teeth to better see the behavior. I can not figure out why this is happening.
http://goo.gl/SnDGt

Sorry if google hasn't converted the videos yet.

#### kf2qd

#5
##### May 10, 2012, 12:05 am
Check your wiring - FOr any stepper problem first double check the wiring, second check the code.

#### imagiro1

#6
##### May 10, 2012, 12:43 amLast Edit: May 10, 2012, 12:48 am by imagiro1 Reason: 1
kf2qd, I did that a bit ago I missed a ground. But that didn't fix the problem.

I'm using an o'scope connected to the pins on the Arduino and stepper motor.
goo.gl/xN3YP
The problem is when both pulses change at the same time. This is shown in the picture on the first pulse. You'll see one go high and one go low at the same time. This happens again right after the mid-line of the screen. So it's software...

I found my problem.
Code: [Select]
`const int stepsPerRevolution = 48;`
I had this set to 7.5 because that was my step size. Well, this number needs to be 48. 1 revolution = 360 / 7.5 = 48
I looks like that 7.5 was the perfect number to cause the pins to change at the same time causing the problem. It's working perfectly. Also the center taps need to be connected to the power source. Not 100% why. Hopefully the machine book at home covers stepper motors.

Stepper working.
http://goo.gl/Wzjls

#### kf2qd

#7
##### May 10, 2012, 04:47 pm
Do to using integer math, any time you put a non-integer value in you would wind up with a count that would reset, and thus multiple pins would be affected.

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