stepper motor issue

Discussion in 'The Projects Forum' started by maham ahmed, Jul 7, 2014.

  1. maham ahmed

    Thread Starter New Member

    Jul 7, 2014
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    i am striving to drive my 5 wire unipolar stepper motor through microcontroller...i am using driving ic l293dd. my motor model is Em 284 ,178936 ,stp.42D221-01. i have searched alot about this motor on the internet but i couldn't find any specification. now i am giving a pwm signal generated by pic 16f877a to both of the enable pins of l293dd ic and both enable pins are short.
    Frequency of the pwm signal is 1.22khz and duty cycle is almost 36 %.
    At this motor is taking steps but it is missing the steps and is not running smoothly and is causing vibrations.
    is there any probllem with the pwm signal's freuency or duty cycle ? can i give pwm signal like this?or should i give 5 v constant to both the enable pins.
    why motor is missing the steps?? Also my l293dd heats up during working.
    plz help me out ......








     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    enable pins should just be high or low not a pwm.
     
  3. Edmunds

    Active Member

    Sep 27, 2010
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    Steppers do not require pam in a traditional sense (servo, dc motor speed control) as already stated. What colours are the 5 wires?

    You should be generating pulses - both for direction and steps. PWM is also pulses, but here the principle is somewhat different. In case of steppers, one pulse will give you one step. Sometimes you only want one step/pulse for the motor to move something x millimetres. Or more likely 0.000x millimetres. The two direction wires basically want L/H or H/L format pulse to throw the motor in another direction.

    L293DD is fine, but does not help much with the intelligent part of stepper control. Why don't you use one of those?


    Good luck,

    Edmunds
     
    Last edited by a moderator: Jul 7, 2014
  4. MrChips

    Moderator

    Oct 2, 2009
    12,449
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    Yes, what are the colours of the five wires?
    Five wires to me usually mean that this is a 4-winding stepper with one common.
    You can verify this with an ohmmeter test. If that is the case I believe that the L293D is not the proper controller to use.
     
  5. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    MrChips is right, the 5 wire unipolar motor cannot be driven from bipolar style h-bridge driver like a L293D.

    It can only be driven from a unipolar driver with 4 switching devices, like 4 FETs or a ULN2003 IC etc.
     
  6. sanuzr

    New Member

    Mar 29, 2012
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    Two types of Stepper Motor are there, Unipolar (Have 4 Wires or two coils) and Bi-polar (may have 5 or 6 Wires depending upon the manufacturer, it has 4 coils inside). What ever you have is uni-polar having 5-wire. In this case, one of the wire is common for all coils and the 4-wire are for the four coils. You do not need a L293 or any H-Bridge to operate an uni-polar stepper motor (But is needed in the case of a bipolar). Also there is no need of PWM (just like the DC Motors) to operate a stepper. The right way to drive a stepper is that, give pulses of certain duration say 5ms to each of the the Coils sequentially. Make sure you are giving the pulse in the proper sequence else it wont rotate rather it will only vibrate. Lets assume that the proper sequence in the following circuit is => Turn ON A for 5ms => Turn OFF A & Turn ON B for 5ms => Turn OFF B & Turn ON C for 5ms => Turn OFF C & Turn ON D for 5ms => Turn OFF D & Turn ON A for 5ms and so on. So if you alter a sequence, the motor will move forward one step and again move backward one step in the altered step and it will not rotate. The following circuit will work for you provided you are giving the sequence perfectly. Connect the terminals A,B,C,D to any four GPIOs of your Arduino, Give proper Voltage for the Operation of the Motor at V-MOTOR. Note that Pin No-8 is hidden in the schematic and it should be connected to the GND of Motor Supply (which should be connected together with the GND of your Arduino). Hope this solve your problem...
     
    Last edited: Jul 8, 2014
  7. Alberto

    Active Member

    Nov 7, 2008
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    36
    A unipolar stepper motor can be driven with a bipolar driver providing that the two center taps are isolated from each other. The OP unfortunatly has the center taps connected together, with only one wire available so the two coils are electrically connected and this makes this type of motor uniquely unipolar.

    Alberto
     
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    So 4 of us agree now.

    Anyone else want to agree too? ;)
     
  9. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    ooo..ooh... me too. (raises hand)
     
    THE_RB likes this.
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