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Topic: Stepper motor to weak. (Read 964 times) previous topic - next topic

jaapbaardaap

Hello,

I've recently purchased 4 mercury stepper motors and 4 easydriver stepper motor drivers. I got them working, turning the right amount of steps etc. But when i put the wheels on and mount the motors on the chassis of my robot the motors dont have enough power to start riding. they only vibrate but cant get to the next "step". I've tried to make the delay betweens steps much bigger (even to 5000 microseconds) but the motors dont have the strength to start turning.

This is my setup:
The weight of the robot is not that heavy. Only the motors, one hard cartboard plate, my arduino and a 6 cell AA battery pack.
The easydriver gets his power from the arduino board and works on 5v.
I was so stupid to try a 12 volt adapter to power the easydriver but it got really hot and I got the same results.
The stepper motor makes 200 steps per revolution.

I can't find a solution myself, I have googled 2 days but i can't find a real solution.

Thanks for all the support on this forum :)

MarkT

[ I won't respond to messages, use the forum please ]

jaapbaardaap

Datasheets
Easydriver: http://schmalzhaus.com/EasyDriver/
Stepper motors: http://www.sparkfun.com/products/9238

I've wired the motors the same way as in this example: http://bildr.org/2011/06/easydriver/

The pictures of my setup are on my other computer but I will post them this evening.


jaapbaardaap

The biggest question is, what factors improve the torque of a stepper motor?
the one i know is speed, the slower it turns the more torque.
But does the voltage invluence the torque aswel?

jaapbaardaap

YEEY, I think I have the solution. My stepper driver probably burned out because I was using a 12V AC adapter. Forgot to look if it was DC... stupid mistake XD. I think if i connect a 12V DC adapter everything will be fine and the motor will work much better. lets hope that is the fix.

Grumpy_Mike

Quote
But does the voltage invluence the torque aswel?

Yes it does.

However it can also cause excessive current through the motor. If that is so you need a chopping regulator like this one:-
http://www.pololu.com/catalog/product/1183
Then you can wind the voltage much higher without the motors getting too hot.

jwatte


Datasheets
Easydriver: http://schmalzhaus.com/EasyDriver/
Stepper motors: http://www.sparkfun.com/products/9238

I've wired the motors the same way as in this example: http://bildr.org/2011/06/easydriver/

The pictures of my setup are on my other computer but I will post them this evening.



If you lift the platform, do the wheels actually turn? Sometimes, connecting the windings wrong will just make the motors grind in place, working against themselves. Also worth checking that you're turning the motors in opposite directions on opposite sides :-)

A gearbox will provide better torque, but slower speed, if what you really need is more torque.

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