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I'm trying to control a stepper motor with my Duemilanove. It's one of the motors available from SparkFun: https://www.sparkfun.com/products/10551? But I cannot get it to behave. Setting aside the driver (I'm trying to use a SN754410 as detailed here: http://arduino.cc/en/Reference/StepperBipolarCircuit) issues that I'm having, just hooking up the motor to the Arduino isn't working. I'm powering it with 12V, as necessary, and have the four wires from the stepper going into pins 8-11. But when I load and run any of the programs in the stepper library (StepOneRevolution, etc.) the motor simply 'shakes' - it twitches forward slightly, then back, and it's not nearly an entire step, as this motor is supposed to be doing a 7.5 degree step angle. I've switched voltage supplies, sketches, and everything else I can think of, but I can't get this motor to 'step.' (I also know it's not the motor, as I have several of them and they all respond the same.) Can anybody offer me some advice or some additional reading material? I'm stumped here, and my Google-fu has failed me thus far.
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I'm powering it with 12V, as necessary, and have the four wires from the stepper going into pins 8-11.
Stop right there. That arrangement will damage your arduino from both excess current and excess voltage.
You need some sort of driver.
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OK, so before I deal with building a driver from the 754410, can I just plug the stepper wires into pins 8-11, use the 5V from the USB power, and test it that way? I was experimenting with 12V only because that's what the motor's rated for, and I was thinking that perhaps some of my problems were coming from insufficient voltage to the motor.
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OK, so before I deal with building a driver from the 754410, can I just plug the stepper wires into pins 8-11, use the 5V from the USB power, and test it that way? I was experimenting with 12V only because that's what the motor's rated for, and I was thinking that perhaps some of my problems were coming from insufficient voltage to the motor.
No.  You will exceed the current rating of the pins.
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*sigh* All right - thanks for your help, GM. Should I safely assume that if I still can't get the motor to work, then it's because I've built the driver incorrectly? I wish I could find some more info on building it than a simple little .jpg file on the Arduino bipolar stepper page. Seems everybody's using the L293 series instead.
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Pinouts for the SN754410 are the same as the L293. Given a choice between the two the SN754410 is preferred as it has slightly higher power ratings.

In my experience the biggest problem with these chips is having sufficient/clean power. If your supply is noisy or cheap you'll have problems.
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Have you downloaded the data sheet?

This is something I have just knocked up for you.

* Stepping driver.pdf (20.73 KB - downloaded 15 times.)
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I'm powering it with 12V, as necessary, and have the four wires from the stepper going into pins 8-11.
Stop right there. That arrangement will damage your arduino from both excess current and excess voltage.
You need some sort of driver.

Indeed - you also need to test pins 8 to 11 to see if they are still working properly - directly connecting an inductive
load (all motors are inductive loads) to sensitive electronics is a recipe for fried components.
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Thanks, all. GM, especially - thanks for that pinout diagram. Either I was reading the other one wrong, or simply doing something wonky with my wiring - but I finally got it working.
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