Stepper motor drive details

[johnxavier]

Hello all
I am currently working on a project to drive a stepper motor (bipolar). I am using national make LM18200T. The device capable of withstanding upto 55V and 3A maximum drive. It has very low on resistance and hence the device is not getting heated up even continous drive upto 2A.But I have a great problem with the device i.e cost. It costs around $8. For huge volume I cannot afford the prize.
Can anyone guide my idea about going for h-bridge drives. Can transistors be used to form the h-bridge to drive the stepper motors. Will it be capable of driving upto 3A continuous. Will the device get heated at this current.
Please suggest some widely used transistor (cheapest) for this h-bridge application.
I have tried a transistor drive for unipolar stepper motor drive using TIP122(motorola). The device get heated up when the stepper motor is holded at one position. Is there any option for reducing the heat produced.
The suggestions from you will be timely help for me
Thanks and regards,
JOHN XAVIER

 

[cbarn24050]

Hi, you could try a L298 they are good for 2A or L295 good for 2.5A. A discrete solution might be cheaper in parts but you have extra board space and assembly costs.

 

[johnxavier]

Hi cbarn24050
Thanks for your suggestion. The device L298 I have tried. But the device is found to be heated after some time. This happens when the stepper motor is stalled at a position.
Is there any way to reduce the heat of the device. Can you tell why the device is heated up?.
Rgds,
JOHN XAVIER

 

[cbarn24050]

Hi, the 298 has bipolar darlingtons in the output stages. As you cannot saturate a darlington there will allways be a voltage around 1.5 to 2.5 accros the conducting device so with 2A this means 3 to 5 watts each side of the bridge. 4 legs in each package gives a total of 12 to 20 watts, add in some switching losses and flywheel diode losses and you can see why it gets hot. If you need full power all the time you need to use the multiwatt package (L298N ) and good heatsinking.

 

[jbartos]

Suggestion: Visit

http://www.hsimotors.com/drives/

http://eio.com/jasstep.htm

http://www.alltronics.com/stepper_motors.htm

(14.95$ for two bipolar motors)

http://mechatronics.mech.northwestern.edu/mechatronics/design_ref/actuators/stepper_drive2.html

etc. for more info

 

[tiki]

Hi johnxavier,
I'm also involved in a project to build up steering electronics for bipolar stepper motors. 3 channels, 60V, 2,5A, fitting onto a Eurocard (160mmx100mm) for an automotive stepper motor test bench. The same problem: heat. I found out, that the usual H-bridge-ICs do not solve this. Until now I simulated some example circuits, using Mosfets. It seems to be not easy, to get all secondary effects, like back-emf and switching losses/-peaks out of the simulation. For the first part of the project we decided to use L6207 from STM (with lower continuous current). I'm laso not sure, which control circuit would be the best for microstepping, variable frequency and voltage/current amplitudes. I will use a EPROM control circuit probably.
I am very interested in further discussion about this project, possibly by email, to exchange draft schematics e.t.c.
You will find further information, including email address, on my homepage:

http://www.ibtk.de

(german).
tiki