Unipolar Stepper questions

hi i have a couple questions i can't figure out, i have two airpax 4shg-060a-46s Unipolar Stepper Motors 6v 7.1 ohms 1.8/step. first problem is i know the 3 wire groups and i know the center tap of each coil (5&6) i just don't know what wire is 1,2 and 3,4 am i going to have to take one of them apart?

pink-------------------| |>7.1 ohms black = center tap-----| |>7.1 ohms blue-------------------|

brown------------------| |>7.1 ohms white= center tap------| |>7.1 ohms yellow-----------------|

my next question is from all the reading i'v been doing, 6v divided by 7.1 ohms is going to give me .84 amps but from the code it looks like two coils will be pulled in at the same time, and i'd like to use a computer power supply 5v is this possible on a 6v motor? or will i have to use a mosfet and use the 5v from the chip to switch 6v to each stepper coil ?

i would like to be able to control the cw and ccw rotation and speed if possible, i have an uno and a duemilanove so output pins are a concern.

http://arduino.cc/en/Reference/StepperUnipolarCircuit

On this page there are two different wiring diagrams the first only uses two output pins where the second uses 4 of the arduino. what is the advantage to using one setup over another?

As for the airpax motors i'm unable to find a pdf file for them because airpax merged with another company and i guess the documentation is gone.

In the end i'd like to run 3 motors off one uno if possible, i did see some where there was a shield that goes on the uno that would extend the i/o to 48 through flat ribbing cable or ide cable but i can not find the web sight again to save my life. does anyone know the web page?

thank you for taking the time to answer my questions

first problem is i know the 3 wire groups and i know the center tap of each coil (5&6) i just don’t know what wire is 1,2 and 3,4 am i going to have to take one of them apart?

It doesn’t really matter. If you say 1 is “A” and 2 is “B” then the motor will go one way. If you reverse them the motor will go the other way. Wire it up, see how it runs, if you don’t like it, reverse the wires :slight_smile:

i’d like to use a computer power supply 5v is this possible on a 6v motor?

Sure, it’s always safe to run a motor at less than its maximum voltage rating.

On this page there are two different wiring diagrams the first only uses two output pins where the second uses 4 of the arduino. what is the advantage to using one setup over another?

One uses fewer pins :slight_smile: The 2-pin control scheme only lets you do full-stepping, the 4-pin schemes allow you to do more fancy stuff like half-stepping and wave drive.


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hi RuggedCircuits

my back ground is in industrial elec. so motor voltage to me is critical. but what i'm use to dealing with is 480v ac 3ph up to 300hp. plc's rung logic this is hard lol my whole way of thinking is upside down lol

so i need a uln2004 and i don't have to worry about the amps?

Oh no, you definitely have to worry about the amps. The ULN2803/ULN2004 is only rated for 500mA of ABSOLUTE MAXIMUM current (so stay well away from that). That's a little underpowered for you ~800mA motors.

I'd recommend going to a discrete-MOSFET unipolar drive scheme. You will need 4 logic-level MOSFET's (e.g., NDP6060L) and a handful of resistors. I wish I had a ready link to point you to but perhaps someone else will step up.

-- The Rugged Motor Driver: two H-bridges, more power than an L298, fully protected

For that size motor I would use an L293D dual h-bridge chip. It's readily available for about $2 US and easy to wire up. Here's a link to a schematic: http://www.seattlerobotics.org/encoder/may98/steppers.html.

The L293D is only rated for 0.6A The L293 is rated for 1A

hi
i finally got this to work, the colors are as follows.
yellow coil 1
brown coil 2
red coil 3
blue coil 4
i’m using 4 tip3055’s to control this motor, it seems ok do i need to add diod’s ?

yellow------------------|
|>7.1 ohms
white= center tap------|
|>7.1 ohms
brown-----------------|

red---------------------|
|>7.1 ohms
black = center tap-----|
|>7.1 ohms
blue-------------------|

stepper.PNG