### Author Topic: Stepper motor speed control using a pot  (Read 3796 times)

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#### dsesmg

• Robot Overlord
• Posts: 128
##### Stepper motor speed control using a pot
« on: September 23, 2009, 06:24:49 PM »
Hi, I am trying to control the speed of a unipolar stepper motor using a potentiameter.
The specification of the stepper motor is as below.

-Unipolar
- 1.8°/Step
-Operating voltage : DC 4V
-Current:0.95A/Phase
-Resistance:4.2ohm/Phase
-Inductance:2.5mH/Phase
-Holding Torque:1.6Kgf-cm
-Detent Torque:120gf-cm
-Rotor Inertia:38g-cm

I just need this stepper motor to turn one direction and hopfully, I need to increase or decrease its speed by adjusting a potentiameter.
I once arranged a stepper circuit using two ULN2003 chips to cope with the above stepper motor before. I used Darlington transistor array for a unipolar stepper motor in this tutorial.
http://www.tigoe.net/pcomp/code/category/code/arduinowiring/51
Since the current of the stepper motor is almost 1A, I parrelelled two ULN2003 so that the chip could cope with the motor's current needs.

The circuit diagram of the stepper motor is this.
http://www.flickr.com/photos/34955071@N02/3947745034/#sizes/o/
Could you advise me where and how can I put a potentiameter?

#### paulstreats

• Supreme Robot
• Posts: 1,381
##### Re: Stepper motor speed control using a pot
« Reply #1 on: September 23, 2009, 07:37:37 PM »
you cant directly affect the speed of a stepper motor by limiting the current or potential with a Pot. Sorry.

If you are using a microcontroller to control the stepper, then you can read in the Pot value and adjust the ste speed according to the analog reading

• Jr. Member
• Posts: 11