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[on:]

Hi, I just bought an arduino UNO and I'm getting into this awesome community, I'm trying to control a bipolar stepper motor, and I'm having some issues, the motor is from an old epson printer, I have one EM-236 with 12ohms between its coils and one EM-257 with 8ohms (I'm supplying them with 5V) and following the schematic that uses only 2 digital outputs, the H-Bridge and a couple of transistors, the motor control 1 and 2 are connected to digital outputs 8 and 11, I changed the Stepper stepper(STEPS, 8, 9, 10, 11); line for Stepper stepper(STEPS, 8, 11); and tried with 100 and 200 total steps, (not sure if they use 1.8° for step or 3.6°) but none of them worked, with the OneStepAtATime example the motor does one step in each direction, and with OneRevolution example it just vibrates. can you help me to figure out what am I doing wrong?

EDIT: then I tried the other way with the H-Bridge only and using the 4 outputs to see if I there is a problem with the connection of the transistors or resistors but it worked pretty much in the same way, and with 240 steps in the OneRevolution example the motor rotates half a turn in one direction and half in the oposite, is it posible that I'm jus missing the total number of steps for the motors? in some places I saw that they are supposed to be 200 but I'm not so sure...

Hope you can help me.

Regards.
Andres.

[Reply #1 on:]

Some steppers are 1.8 degree, 200 steps. Some are not...
The Epson steppers might be 3.6 degree, 100 steps.

You will need two H bridges to control a bipolar stepper, one for each coil.
What driver are you using, where is the schematic?

Is this it: http://arduino.cc/en/Reference/StepperBipolarCircuit
In this case the L293D is a dual H-bridge.

If it just vibrates then you have some motor wires mixed up...
Or you might be trying to move it too fast with too little current.

Try reversing one coil and slow it down...

[Reply #2 on:]

Thanks for the reply, yes, I'm using that L293D, and following that schematic, I tried both of them, one thing that I'm not sure is, I'm supplying all the +5v with an external power supply, should I supply it from the arduino instead? and use the external only for the motor?
1 out and 2 out are connected to one coil and 3 and 4 are connected to the other.
Right now with 200 or 100 steps it doesn't rotates at all, but if I use something around 240 it rotates, not perfect but at least it moves.

[Reply #3 on:]

If you're putting 5V through an L293D you won't be getting anything like 5V to the windings since the driver has darlington output stages that use up 2 to 2.5V - you might get upto 3.2V out or so.

Do you have specifications for the two motors?

[Reply #4 on:]

I don't have them, I just found that the motors work with 7V, or 5 I saw that people say in some pages, what would be the best way to connect the power supply? I have 5V and 12V outputs but I can find something else to power it, should I connect all the 5V to the arduino output and the motor supply to the 12V? and the gnd? should I use the one from the Arduino or the power supply?

[Reply #5 on:]

The L293D has a maximum continuous output rating of 600mA. Therefore, using the stepper with 12 ohm windings, you need to limit the voltage across each winding to 7.2 volts. I would take the 12v supply to the motor supply input of the L293D through four silicon rectifier diodes in series, which will drop it to about 9v. This will give you about 6v to 7v across the windings.

Try stepping the motors slowly until you have got it working.