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Small Arduino USB Stepper Motor - Need Help

Former Member

I'm overwhelmed by all the stuff out there for building this small project, and I am very unsure of what I need to buy.

 

1. First Question. What kind of motor?

 

I only need the motor to make one complete rotation, both forwards and backwards, and able to make the smallest micro movements, it can run on the smallest of power, as it won't be doing much but making slight movements in timed sequences.

 

2. Second Question. What Arduino board do I use?

 

The motor will be controlled by a computer, so I'm thinking USB cable would be the best connection.

 

3. Third Question. What software and program options do I have?

 

I want to be able to create different programs for turning the motor, that can repeat if I want them to, or take a program and make it random so it stays constantly changing.

 

4. Fourth Question. I need to hook the motor to a small knob, how do I do it, what do I use?

 

The motor is going to turn a knob on a small hand held unit, so I'm thinking of replacing the knob with a type of gear and adding the same to the small stepper motor and connecting them with a belt.

 

 

I've been searching for a few weeks, and I would hate to buy several motors, several gears, several boards, and still end up with a bunch of junk that does nothing. I really need this and I need it to work.

 

I'm thinking it might be easier just to hire someone that knows what they are doing.

  • 0

    1. This sounds like a great project for a small servo, which would be low power draw, allow simple 1* increments (in both directions), and be controlled with 1 Arduino pin. If you need more than 180* of rotation, look for a continuous rotation servo. Do a little research on servos, but don't worry too much about getting "the wrong one". They are easy to use, cheaper than a stepper, and almost universally practical.

     

    2. For beginner Arduino use, the Uno is a great platform and it has the USB interface you are looking for.

     

    3. You can use a program called Processing to write a user interface to switch between different "programs" or use a mechanical switch to cycle through modes inside your code. Use of a random() function is possible inside the Arduino platform, also.

     

    4. Connecting the knobs is a classic mechanical issue, one I've dealt with too many times. I'd reccomend a tiny elastic belt system, although a toothed connection may be just as simple for your application.

  • 0 in reply to Former Member

    I just looked up servo motors, and they don't appear to do tiny micro movements for exact positioning, and not being able to turn 360* would definately be an issue, so I think a stepper motor would work best, from what I've seen and read on the internet so far about motors.

     

    I found this video which shows a stepper motor making micro movements

     

    Which of these motors should I get?

    https://www.sparkfun.com/categories/178/

     

    There are four stepper motors on that page and I don't know what is different about them!

  • 0 in reply to Former Member

    Hi Jason,

     

    There is not enough information to know for sure unfortunately (and I wouldn't want to suggest one, for you to find out it's not the best choice). If you think the item you want to rotate doesn't require much force, then a small stepper motor is sufficient. Also, you'll want to check if the motor is unipolar or bipolar, so you can select the appropriate motor control circuit.

    Bipolar motors will have more torque, but need a special circuit (which probably Sparkfun do sell).

  • 0 in reply to shabaz

    Does unipolar mean it only goes in one direction?

    And does bipolar mean it goes in both directions?

  • 0 in reply to Former Member

    Hi Jason,

     

    No, it refers to the wiring of the coils - with a center breakout, it is possible to simplify the drive for unipolar wound motors, but with reduced torque.

    Both types of motors can rotate in either direction.

  • 0 in reply to shabaz

    I took another look at the four stepper motors, and I'm thinking the one with 400 steps/rev and only needs 3V would be the best for accuracy and low voltage.

     

    Stepper Motor - 68 oz.in (400 steps/rev)

    https://www.sparkfun.com/products/10846

     

     

    but it is a bipolar motor so I need a driver. Right?

     

    EasyDriver Stepper Motor Driver

    https://www.sparkfun.com/products/10267

     

     

    for the board, the unio sound good?

     

    Arduino Uno - R3

    https://www.sparkfun.com/products/11021

     

     

    and the unio requires this software........

     

    http://arduino.cc/en/Main/Software

     

     

     

     

     

    Would this be the correct USB Cable?

     

    https://www.sparkfun.com/products/513

     

     

    and will this casing work for both the UNO and Driver or just the UNO?

     

    http://www.robotshop.com/productinfo.aspx?pc=RB-Ard-16&lang=en-US

  • 0 in reply to Former Member

    I would like to jump in again before you go with the stepper motor. I really reccomend going with this continuous rotation servo. It will give you 360steps/rev (because you can set it in 1* increments) and can simply be plugged into the Uno without any seperate driver. The voltage lines up nicely with the 5V output on the Uno, also. 

  • 0 in reply to Former Member

    Will the software and program for the stepper motor also work with the servo?

     

    The servo is about the same price as the stepper, so I could get both and compare the two in performance!

     

    My main concern though is that a servo is not made to make micro movements and a stepper is, so if 400 stopping points are important, then why would a servo be better? Can a servo stop at 400 different stopping points like a stepper?

  • 0 in reply to Former Member

    The software is good for any arduino project you can think of (from motor control to home automation to GPS navigation), the difference is in the code you write. As far as accuracy is concerned, a continuous rotation servo can be turned (and held) to any degree value. That means it has 360 steps/rev. That's barely less than the 400 steps/rev you are looking at in the stepper.

  • 0 in reply to Former Member

    Is it confirmed that the product referred above can be rotated to a defined position? As I understand, it appears to be a pre-modified hobby servo which uses PWM to control speed (not position). (Some of the comments on that page also seem to state this, but I have not used the product so I can't say for sure). The modification entails removing the internal potentiometer, so that there is no longer any feedback on position.