Choice of motors for driving wheels

Discussion in 'The Projects Forum' started by ActivePower, Jul 10, 2012.

  1. ActivePower

    Thread Starter Member

    Mar 15, 2012
    155
    23
    Well, I have just begun programming a microcontroller recently and am currently trying out driving motors for my obstacle avoiding robot project.
    I have been researching various motor types for driving the wheels of the bot and have the following questions:

    1. Seems like servo motors are pretty good in getting to the correct position you tell them to get to but suffer from lower torque problems. As an advantage however, you could just connect them directly to the MCU and get them working.
    It looks like they aren't exactly the right choice for driving wheels...might they be of use to mount the sensors and stuff?

    2. Stepper vs Geared DC: This is where I am really stuck.
    Based on what I read you can interface a DC motor through a L293 driver IC and be done with it. Also the gear reduction provides great torque for the wheel drive.
    However, stepper motors can be configured in open loops and are brushless to make things better.

    Also the speed I have in mind right now is 15 cm/s. Is that good enough for an obstacle avoiding robot?

    Thanks!
     
  2. mcasale

    Member

    Jul 18, 2011
    210
    12
    My experience is that stepper motors are VERY easy to drive from an MPU, but you need a driver that can handle the current. The firmware keeps track of the position by the number of steps.

    Only you can determine what's good enough for your project.
     
  3. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    Depending on the size and weight of your bot, you could do with servos that were modified for full rotation (most typical RC servo do not rotate all the way around they have a mechanical and electrical interlock that prevents them from doing so.), plus, you could run your bot of of 4 AA batteries for power to the motors and a separate 9 volt for the uC... and you could use unmodified servo for sensors such as a Ultrasonic transducer to pan it back and forth to detect obstacles in the way while following lines, etc....

    Here is one of my line following robots with modified futuba servos for driving the wheels... http://www.morse-code.com/id115.htm

    and here is another robot of mine that also uses 2 modified servos >>> http://www.morse-code.com/id40.htm

    and a walker bot which uses 12 unmodified servos to "walk" >>>> http://www.morse-code.com/id110.htm
     
  4. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234

    They may be easy to drive, but need complicated electronics to properly run.... for a line follower robot, simple low voltage DC geared motors or modified servo motors would do quite well for the novice or beginner....
     
    ActivePower likes this.
  5. x1222

    Member

    Oct 22, 2011
    31
    0
    I used a modified Hitec-422 servo for my line follower. Its specs seem quite standard for cheaper servos. The torque on servos also don't seem to be that much worse than geared DC motors. The servo was easy to get working for wheels, controlling directions, and what not. No problems there. However, the speed of the servos were not very impressive. If you just want to get it working, I'd say servos. But if you care about speed and don't mind extra work go for geared . I've never used steppers, but most people seem to say they aren't worth the hassle.
     
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