stepper problem

Discussion in 'Programmer's Corner' started by kumar'puneet, Oct 22, 2008.

  1. kumar'puneet

    Thread Starter New Member

    Oct 22, 2008
    2
    0
    I am trying to move a bot with bipolar 4 wire stepper motors. i have made the bot. But it is not moving. not enough torque. when i lift it , both the wheels move properly. i have used L298 driver. i am using sanyo 2700 mAh batteries. i am providing 9 volts. my bot is approx. 1 kg.
     
  2. kumar'puneet

    Thread Starter New Member

    Oct 22, 2008
    2
    0
    i haven't used l297. and i have shorted all the enable pins in the l298 chip to +5 v. i have given common ground to microcontroller and the l298 chip.I am not able to move the bot. It is just shaking instead of moving forward. please help
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Welcome to AAC.

    I merged your posts since they are closely related.

    It would help if you could post up the schematic of your circuit. Also, what is the rating of your stepper motors?
     
  4. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    Shaking usually means your step rate is too high or your commutation is incorrect.

    You should disconnect the motor mechanically and simply seeing if you can get it to turn. If the problem remains, then try to slow down the step rate. If that isn't it, then check out the commutation.

    Not knowing the rated voltage of the stepper doesn't help. It may be designed for higher voltages, so your 9V might not be able to produce enough (current / change in current) for the motor to step.

    Steve

    Steve
     
  5. Papabravo

    Expert

    Feb 24, 2006
    10,145
    1,791
    Slow down the stepping rate. You'll get way more torque at low speed.

    If that works then you need to ramp the velocity up and back down again carefully avoiding the systems mechanical resonance.
     
  6. atferrari

    AAC Fanatic!

    Jan 6, 2004
    2,648
    764
    Hola PB,

    How do you know when you are in the mechanical resonance range values of a certain system?
     
  7. Papabravo

    Expert

    Feb 24, 2006
    10,145
    1,791
    If you try to start the motor at that speed it will vibrate without moving. For most systems it is typically in the 200-300 Hz. range. Your mileage may vary. The only solution I know of is to ramp the velocity up and down to avoid this range.

    Example: Say the resonance is at 250 Hz. You might start at 25 Hz and then go 50, 100, 200, 400... Then coming back to a stop you would go 400, 200, 100, 50, 25,...
     
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