Low Resolution, High Torque Stepper Motor?

Discussion in 'The Projects Forum' started by nickos, Sep 2, 2009.

  1. nickos

    Thread Starter New Member

    Sep 2, 2009
    My basic question is: Are there low resolution stepper motors available that have reasonably high torque and are cheap?

    The specifics: I'm working on a project that currently uses a basic DC motor with a gear head. The stall torque is supposedly 92 oz-in (full specs here), and I need a rotation speed of somewhere in the ballpark of 250-300 rpm under load. It would be nice to have some idea of how fast the motor is spinning, so I've considered using a stepper motor. The thing is, I don't need a very high resolution at all. In fact, it's okay if I only know when the motor has made a full spin or maybe half spin. The alternative then is to mount some magnets and use a Hall effect sensor with the DC motors. But I know there are other advantages to using stepper motors instead (like increased durability, quietness, etc.).

    So, back to my question. Are there stepper motors that provide that kind of torque, at those speeds, and are pretty cheap? The motor above is $11, just to give you an idea. I know that resolution can drive up the cost of a stepper motor, so that's why I threw the low resolution info in there. I don't care if it only has four steps. I just want to know when it has rotated once or so. :) So is it worth it to go for steppers, or should I stick with the gear motor that I am using now? Any opinions or insights would be greatly appreciated.

  2. jj_alukkas

    Distinguished Member

    Jan 8, 2009
    There are lots of steppers and BLDC motors in the 10-15$ range. Better would be to check online ordering sites which provide the full details. Even if you find a fast one, get a gear set with higher gear ratio to reduce the speed factor and again you get even more torque. Apart from than, I'm no expert in DC motors. The BLDC ones with good resolution come with hall effect sensors and speed controllers and an 8-wire config. Just a point.
  3. nickos

    Thread Starter New Member

    Sep 2, 2009
    Thanks a lot for the pointers. My follow-up question then would be: Could you (or anyone else) recommend some good places to get stepper motors at those prices? I'm used to getting electronic components from places like Mouser, Digi-Key, etc. But they don't have stepper motors that cheap (or with the torque I need).

    Also, would these motors need an additional controller or driver to operate, or can I control them directly from a microcontroller? I guess if I have to spend $15 on a stepper motor plus $xx on a controller plus $yy on a gear set, then it would be much more cost effective just to add the Hall effect sensor to my current motor set-up.

  4. beenthere

    Retired Moderator

    Apr 20, 2004
    For the kind of torque you need, it may be a lot more expensive. look over the stuff at Omega - http://www.omega.com/pptst/OMHT_Series.html

    You will need a driver for the motor, probably controlled by a microprocessor, as the motor will have to be started at a low RPM and get ramped up to the desired speed.