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hi, i'am planning to build a simple arduino based plotter x,y axis.i've got two stepper(unipolar, got from an old hp printer)
i dont want use any shield.can anybody show me a simple schematic. i think using 4 transistor and flyback diode will do the job.
is it correct? please correct me if i'am wrong
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Manchester (England England)
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Have a read of:-
http://www.thebox.myzen.co.uk/Workshop/Motors_4.html
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thanks for replying.
the motor has 5 wires, 4 for supplying pulses(so  4 transistor and 4 flyback diode) and other one, ground.
[grumpy_mike] thanks for the link but i was hoping not to use specific stepper driver ic
Isn't there any simpler method . i once built an  h-bridge for dc motor and it was lot simpler.
thanks again.
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Hi, Some other basic stepper information here: http://arduino-info.wikispaces.com/StepperMotors

And you can read the schematics of some motor drivers here: http://arduino-info.wikispaces.com/MotorDrivers
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[KE7GKP] i actually  have the datasheet for the motors.(current,volatge rating, N vs.T graphs.............)
again hasn't anyone built stepper driver using discrete parts rather than by using specific IC.
Feedback are most welcome.

thanks for all who replied.
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[KE7GKP] :http://www.eminebea.com/content/html/en/motor_list/pm_motor/pdf/pm55l048.pdf this is the link to the datasheet.
I hope that this answers your question . please reply i need all the feedback i can get
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Sorry that was the link for bipolar stepping motors, this is for unipolar:-
http://www.thebox.myzen.co.uk/Workshop/Motors_3.html

The data sheet shows to need to drive it at 24V with 800mA per phase. As there will be 2 coils on at any one time that means you need 1.6A capacity at least, so best get a 24V 2A power supply.
Just treat them like ordinary loads, so a logic level FET in each coil will suffice to drive them.
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Quote
Grumpy_Mike

it's a unipolar stepper . i measured the coil resistance and got 30 ohm as said on the data sheet.
can i use darlington power transistor,the FETs are quite expensive here.
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Yes if the darlington can provide that amount of current, they will get warmer but should be fine.
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Grumpy_Mike
Yes if the darlington can provide that amount of current, they will get warmer but should be fine.
thanks i'll try it out .
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i tried the circuit but instead working with power transistor [for testing purpose] i used  bc547 general purpose transistor to control a smaller stepper motor. the motor worked fine with follwoing schematic however  the series resistor which is used to limit the current to the transistor becomes very hot . is excessive heating common in stepper driver .
Are there any method to reduce it.(to reduce heat ,i cant actually use resistor with higher value, it's connected in series with the motor so the current will decrease and the motor won't rotate


* stepper.JPG (11.07 KB, 397x381 - viewed 15 times.)
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Put the current limiting resistor in series with the motor and switch the whole lot through the transistor. What you have is called shunt control and is very inefficient as it draws more current when the motor is off than when the motor is on.
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the common wire for the stepper needs to be at ground.if we switch current by placing the motor on the collector side the common ground will be maintained at the saturation voltage( in this case at about 0.2 v)  doesn't that cause problem with other part of the circuitry.i am not controlling a 2 wire dc motor , in the schematic above i only showed the connection of 1 wire out of 4 that is connected to the ground in the same way.
please, correct me
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the common wire for the stepper needs to be at ground
Why?
Normally with a four coil motor it is at the positive rail.

If it has to be at ground then you need to do the switching with PNP transistors. Not like you have shown.
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Why?
Normally with a four coil motor it is at the positive rail.

If it has to be at ground then you need to do the switching with PNP transistors. Not like you have shown.

thanks , that would solve my problem. it didn't came to my mind that i could connect common to the positive rail.

Again thanks very much [ Grumpy_Mike]
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