Page 1 of 2 12 LastLast
Results 1 to 10 of 16

Thread: DC Motor - Power Problem

  1. #1
    Junior Member Newbie
    Join Date
    Mar 2007
    Location
    Mumbai
    Posts
    7

    Default DC Motor - Power Problem

    I just made a bump-and-go robot (hits an obstacle turns around and speeds off in a diff direction)...it worked fine on breadboard but now when i place wheels on ground it doesnt move, but works when held off the ground.

    Motors - 5V, 100 rpm
    Battery - Duracell 9V

    What should i do to fix this problem? =/

    Cheers
    Vyder =)

  2. #2
    Member Android
    Join Date
    Oct 2007
    Location
    Mumbai
    Posts
    89

    Default

    Hi,
    The Torque of your motor is very low.

    1) Try to minimize the weight of your robot
    2) Go for a Higher Torque motors


    http://triindia.co.in/shop/product_i...products_id=34

    Best regards,

    pratik

  3. #3
    Senior Member T-1000 debu's Avatar
    Join Date
    Jun 2007
    Location
    New Delhi, India
    Posts
    338

    Default

    @Vyder: Pratik is right, you probably need a higher torque motor, or, it is possible that your battery is dying. Try again with a fresh battery. If your robot, still does not move, you need to replace your motors.

  4. #4
    Super Moderator T-1000 docel's Avatar
    Join Date
    Sep 2005
    Location
    BANGALORE
    Posts
    1,441
    Blog Entries
    3

    Default

    Are the wheels mounted directly on the motor??
    if so, must use a geared motor.

    or, use the shaft of the motor touching the ground as the wheel ......
    docel
    ^Anything is possible..
    after YOU prove it!!

    http://bangalorerobotics.tripod.com

  5. #5
    Junior Member Newbie
    Join Date
    Mar 2007
    Location
    Mumbai
    Posts
    7

    Default

    Is a higher torque motor the only way? i was hoping to keep this project cheap...higher torque will mean more expensive (and ill have to wait till saturday to visit lamington rd again...tests at skool... =(

    @pratik: any lighter and this robot will fly...ive used the lightest plastic box I cud find at crawford market...

    @debu: new batteries dont fix the problem...but connecting it to battery eliminator (5A current) made the robot zip around the room...but not a practical solution =P)

    @ docel: yes the wheels are damn light (plastic hub thing with black foam around it...fell in love with them at first sight...)...but wont the shaft slip?...tubing or sumthing for grip?

    Wont a L293D amplify the current or sumthing?

    Cheers
    Vyder

  6. #6
    Senior Member T-1000
    Join Date
    Mar 2005
    Location
    Bangalore
    Posts
    728
    Blog Entries
    7

    Default

    but connecting it to battery eliminator (5A current) made the robot zip around the room.
    If it did, use normal AA battery!!! Novino, Nippo....
    series connect it to get your required voltage!!

    It should work - never underestimate these old friends - even though they wont last much long.

    You can use rechargeable batteries - Nicd or Nimh. economical in the long run -

    9V batteries are useless to drive motors. NEVER use them to drive motors.

    just curious - the motor is 100 rpm?? so it have to be geared already!! or is it??
    .... I didnt do it ! ....

  7. #7
    Junior Member Newbie
    Join Date
    Mar 2007
    Location
    Mumbai
    Posts
    7

    Default

    9V batteries are useless to drive motors. NEVER use them to drive motors.
    why?

    @ Allbits: Thanx!...ive got some rechargeable batteries lying around...going to go try it right away...and how is a 1.5 V battery better than a 9V??...
    I'm not entirely sur what "geared" means...i hvnt added gears if thats what you are asking...

    Thanx again,

    Cheers
    Vyder

  8. #8
    Super Moderator T-1000 docel's Avatar
    Join Date
    Sep 2005
    Location
    BANGALORE
    Posts
    1,441
    Blog Entries
    3

    Default

    If it draws 5A, if it "zips all over" and if it doesnt start off on low current, then it MUST be a wheels attached to the Motor direct, and not a geared motor!!!

    You said 5v 100rpm, so it is certainly a geared motor. In that case, it should move a weight of around 1kg easily. If you bought it for Rs. 175/- at L road, then the current should not exceed 300ma @ 12v.

    1. Allbits meant 1.5V cells in series ( a "battery" of 6 cells in series) to give 9v.
    The 1.5V cells are ~1AH, where as the 9V bat is ~ 400mAH. Besides, these batteries have hi internal resistance and limit current.
    2. The Nicds and Nimhs have very low internal resistance. This allows large current through the load.
    Simply put, the 1,2v nicd will give better motor performance than the 1.5v cell.

    3. I asked you the question: have you attached the wheels to the motor shaft?? If you cant count the no of rotations of the wheels, then it is too fast. If it runs off the ground and not on the ground then the torque ( turning power) is low. You cannot attach wheels to a dc motor without a gear box.

    4. A gearbox is a set of gearwheels that are attached to the Motor shaft. The output shaft is attached to one of the geared or 'toothed' wheel. The geared combo will reduce the Motor speed by the teeth ratio and increase the torque correspondingly in the same ratio. Torque is the

    For eg: a DC motor will have an average RPM ( Revolutions Per Minute) of some 3000 to 20000. The torque will be some 20gms/cms. This means the motor shaft can move or displace 20gms weight for 1cms per revolution. If you tie a weight to a long thread one end of which is fixed to the motor shaft, the thread wind over the shaft when the motor turns. This will lift the weight at some rate ( height per unit time.) This is a crude way of measuring motor torque and is NOT a scientific definition of Torque.

    You can also test the torque by hand. Apply emf to the motor and try to stop the shaft by pressing with your 2 fingers. If the motor stops , it is low torque. If your finger gets burnt then it is hi-torque :lol:

    5. Most cases, the shaft moves the body. The tubing will help increase the friction, as well as the torque (more or less diameter).

    You have a 12v motor i think, and not of 5V. If it is rated at 12V, it will not work on load @ 5V.
    docel
    ^Anything is possible..
    after YOU prove it!!

    http://bangalorerobotics.tripod.com

  9. #9
    Senior Member Cyborg
    Join Date
    Nov 2006
    Location
    Bangalore, india
    Posts
    244

    Default

    Just increase the supply to motor, use hbridge at high potential than your circuitry if your circuit is having any 5volt specific component .
    Nikhil Chandra | Bangalore

    Imagination is more important than knowledge.

  10. #10
    Member Android
    Join Date
    Oct 2007
    Location
    Mumbai
    Posts
    89

    Default

    hi,
    One more important factor is wheel size
    Simply divide the torque by the radius of the wheel (1/2 of the diameter).
    For example if using a 8 inch Diameter wheels with 1 Kg cm Torque motor then

    (1 Kg cm of torque / 4 inch radius = 0.25 Kg cm of torque)

    Bigger wheels = less torque

    Best regards,

    pratik

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •