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Author Topic: Stepper motor WITHOUT H bridge?  (Read 2939 times)
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So is it possible to control a stepper motor with my arduino without an  H-Bridge?  Maybe some combination of transistors?
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Well, yes, as long as you configure your transistors in an H-bridge configuration smiley-wink

For example:

http://www.solarbotics.net/library/circuits/driver_4varHbridge.html

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Well, yes, as long as you configure your transistors in an H-bridge configuration smiley-wink

For example:

http://www.solarbotics.net/library/circuits/driver_4varHbridge.html

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for the transistors in that link can I also use a 2n3904 or a 2n3906 or even a 2n2222 ?
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Well, yes, as long as you configure your transistors in an H-bridge configuration smiley-wink

For example:

http://www.solarbotics.net/library/circuits/driver_4varHbridge.html

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also, I think the stepper motor has 6 wires. Where would I connect them all?
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Well, yes, as long as you configure your transistors in an H-bridge configuration
An H-Bridge is used for a DC motor, and is not required for a stepper motor.

Don
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So is it possible to control a stepper motor with my arduino without an  H-Bridge?  Maybe some combination of transistors?
For driving a small stepper motor, such as those scrounged from a floppy drive, the easiest way is with an L293D or equivalent.  Make sure you get one with the 'D' suffix otherwise you need eight external diodes.  You can also get by with four garden variety NPN transistors, along with some diodes and resistors.

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also, I think the stepper motor has 6 wires. Where would I connect them all?
Have you done any stepper motor research?  You should have two center tapped coils which means there are six leads if the center taps are brought out separately and five if they are connected together internally.

You are really keeping me busy....

Don
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A lot depends on your motor type. If you have a 6-wire motor it could be driven bipolar (H-bridge) or unipolar (ULN2803 or bank of transistors). Do you know what the motor part number and manufacturer is?

Here is a lot of info on different schemes for driving motors:

http://www.cs.uiowa.edu/~jones/step/circuits.html

The 2N3904/2N2222 are not really designed for motors but will work well enough for "small" motors. That's why it's important to know more about your motor.

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Searching for "stepper motor" at the main Arduino site gets you to this resource:

http://www.tigoe.net/pcomp/code/circuits/motors/stepper-motors
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So is it possible to control a stepper motor with my arduino without an  H-Bridge?  Maybe some combination of transistors?
For driving a small stepper motor, such as those scrounged from a floppy drive, the easiest way is with an L293D or equivalent.  Make sure you get one with the 'D' suffix otherwise you need eight external diodes.  You can also get by with four garden variety NPN transistors, along with some diodes and resistors.

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also, I think the stepper motor has 6 wires. Where would I connect them all?
Have you done any stepper motor research?  You should have two center tapped coils which means there are six leads if the center taps are brought out separately and five if they are connected together internally.

You are really keeping me busy....

Don

Ha ! is that a good thing?  Ill bring home the stepper tomorrow , should I pick one that is small ?
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Well, yes, as long as you configure your transistors in an H-bridge configuration
An H-Bridge is used for a DC motor, and is not required for a stepper motor.

Don

I presume you meant to say "is not required for a unipolar stepper motor"...
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I presume you meant to say "is not required for a unipolar stepper motor"...
You presume correctly!

Don
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I presume you meant to say "is not required for a unipolar stepper motor"...
You presume correctly!

Don

That raises a question for me, since the answer implies you need one for a bipolar one. smiley-lol

Circuit cellar AVR contest 2004 has an entry for a bipolar micro-stepper driver using 2 dacs and 2 TDA2030 chips. I doesn't seem... "H-bridged" to me.
http://www.circuitcellar.com/avr2004/DA3829.html

Unfortunately my knowledge isn't that good yet, so... I'm not sure whether it is or isn't, could anyone tell me more ?

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Unfortunately my knowledge isn't that good yet...
Neither is mine.  The word "required" is pretty strong and I probably wouldn't have used it.  As far as I can tell the unipolar motors (the ones with 5 or 6 wires) are easy to control without the need for an H-Bridge.  The bipolar motors (typically with 4 wires) are easiest to control with a H-Bridge but it's not inconceivable that another method will work.

Don
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The Circuit Cellar AVR 2004 solution does use H-bridges, but they are "hidden" inside the TDA2030 amplifiers. Each one of those amplifiers is capable of sourcing or sinking current, thus serves as a "half-bridge", or one side of an H-bridge.

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In fact the answer is that the H-bridge is needed unless you have a dual-supply setup (such as audio power amps tend to use).  Dual supplies give the ability to reverse the current flow with two switching elements rather than the 4 of a bridge.

I've recently been wondering about various ways to power bipolar stepper motors and cheap audio amps sprang to mind as a possibility, but the need for dual supplies is a disadvantage.

There is a 'hybrid' approach where you use 3 single-rail amplifiers.  One generates a 'ground' rail midway between the supplies - this is connected to A- and B-.  The other two drive A+ and B+ relative to this 'ground'. In effect you fake dual supplies.

Using audio amps means microstepping is straightforward, but you waste power as heat in the amps and you need a couple of DACs to generate the waveforms.

And finally I noticed that there are multi-channel class-D (PWM) audio amp chips available now for 5+1 audio - enough to drive 3 bipolar motors at high efficiency.  However these devices are complex beasts and there are issues like the high input data rates.  Of course a class D audio amp is a full H-bridge internally as it runs from single-rail.
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