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[SOLVED] Problem with stepper motor power

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Newbie level 4
Apr 28, 2011
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I am making a project on sun tracking system. I am using stepper motor PM-42 which is uni-polar with
six wires coming out. When i drive it using Uln 2003, i have a problem with the power. It rotates with
very low power in one direction and it does not rotate in the other direction. Please suggest something asap.

Do you have a six wire unipolar like this


Then if you connect the middle wires 1 and 2 and connect them to the positive supply you can drive A1, A2, B1, B2 with any of the following steps styles using the uln 2003

File:Drive.png - Wikipedia, the free encyclopedia


Yes we have motor same like this. And if we talk about step sequence we noticed a totally different behavior.
When we connect the center wires with +12V and apply sequence as you told it only takes one step and does
not rotate any more. But if we apply sequence only on a1,b1 it rotates in one direction and when we apply
step sequence to a2,b2 it rotates in the other direction.Sequence.JPG
Please also tell me how to increase the power.

The correct sequence is

Winding 1a 1000100010001000100010001
Winding 1b 0010001000100010001000100
Winding 2a 0100010001000100010001000
Winding 2b 0001000100010001000100010
time --->

Winding 1a 1100110011001100110011001
Winding 1b 0011001100110011001100110
Winding 2a 0110011001100110011001100
Winding 2b 1001100110011001100110011
time --->

Jones on Stepping Motor Types

What sequence are you using?


Actually our motor does not work on both of these sequences. I already have mentioned that it rotates in one direction by applying sequence to only two wires i.e. if we apply a sequence like given below it rotates in one direction:
a1: 10101010
b1: 01010101
And it rotates in the other direction if we apply following sequence:
a2: 10101010
b2: 01010101

Can you suggest any other IC which provides more derive current so that we can get more output power.

You can use discrete transistors or a device like


You can check the correct pahse assignment by touching a power supply sequentially with the wires. You don't need transistors for that. Did you check if ULN2003 is suffcient according to the windings resistance of your motor?

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