DC motor controling with L298

Discussion in 'The Projects Forum' started by aGpLT, Feb 6, 2010.

  1. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    Hello all :) So i have a little problem here. My DC motors are 2.4V ~1A and i used this scheme for controling it: [​IMG]
    This circuit is working but when i send high to L1 or L2 motor dont start running i need to rotate rotor with hand when it starts. My input voltage is 5V and thinked that it may be the couse of this issue. And if its problem what kind of stabilizer you advise me ? i searched for one and i get my mind to this one: MLM350T LM350T V-reg 1.2 -33V 3A 4% Sorry for pure english but i think you get what i mean, i hope so :) Thank You for Your help in advance.
     
  2. mik3

    Senior Member

    Feb 4, 2008
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    Put a 100uF 16V electrlytic capacitor near the L298 driver between the 5V and GND. Also, the input voltage of the 7805 has to be greater than 7V.
     
  3. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    Oh sure, i forgot to mention that i am not using 7805 i have power supply 5v directly. So i use same power supply for motor and L298. (Power supply is from computer 5V 15A)
     
  4. mik3

    Senior Member

    Feb 4, 2008
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    You need to put decoupling capacitors near the L298 between the Vs and GND.

    Are you sure the motors are 2.4V ?
     
  5. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    Yeah it's written on motor. Thank You mate it worked ! :) now i need to put big radiator on L298 becouse its hellish hot :) and now its only controling only one motor, it wont get burned of controling two motors ?
     
  6. mik3

    Senior Member

    Feb 4, 2008
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    If you attach the proper heat sink and do not exceed the maximum current rating stated in the datasheet then it will be fine.
     
  7. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    I have one more question if You dont mind, what about power supply for motors ? i still think that i need use 2.4V for it. So what about that stabilizer is it good for it ? :)
     
  8. mik3

    Senior Member

    Feb 4, 2008
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    Will you use PWM to control the motors or just an on/off signal?
     
  9. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    I still thinking about it, becouse motors have quite big load on them and they are rotating slow of that. So i dont see need to use PWM, correct me if i am talking nonsenses ;)
     
  10. mik3

    Senior Member

    Feb 4, 2008
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    I don't understand what do you mean.

    What are the motors driving?
     
  11. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    They have reductors and are driving my robot arm axes. If i didnt answered your question, when i can take some pictures of it :)
     
  12. mik3

    Senior Member

    Feb 4, 2008
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    If you want you can use a 2.4V voltage regualtor which is capable of supplying at least 2 Amps.
     
  13. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    http://www.ipix.lt/desc/53291062/ here its my project. Thank You for Your big help im in debt :)
     
  14. mik3

    Senior Member

    Feb 4, 2008
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    You are welcome. :)
     
  15. aGpLT

    Thread Starter Member

    Jan 21, 2010
    128
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    Hmm, but sometimes it motor wont rotate, maybe i need bigger capacitor to put ? :)
     
  16. mik3

    Senior Member

    Feb 4, 2008
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    What capacitor did you put?
     
  17. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    100uF 16V, i tryed now 220uF 16V and it work better now :)

    And its interesting why motor speed is much slower in circuit than i its connected directly to power supply. :/
     
    Last edited: Feb 7, 2010
  18. mik3

    Senior Member

    Feb 4, 2008
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    Connect a 100nF ceramic capacitor in parallel with the 220uF one.

    The speed is less because of voltage drops across the internal transistors of the L298.
     
  19. aGpLT

    Thread Starter Member

    Jan 21, 2010
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    0
    Hmm, its no good, becouse i have only one power supply, also it have 5V and 12V outputs, but if i use 12V for motors i think they will burn :/ for L298 its not problem i will just use 7805 and its ok.
     
    Last edited by a moderator: Feb 7, 2010
  20. mik3

    Senior Member

    Feb 4, 2008
    4,846
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    You can use 5V or 12V for the motor supply and use PWM to regulate the average voltage across the motor to 2.4V.
     
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