DC Motor Driver - L298

Discussion in 'General Electronics Chat' started by trimbitassorin, Jan 19, 2014.

  1. trimbitassorin

    Thread Starter New Member

    Jan 19, 2014
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    0
    Hello,

    I want to build a small robot with 4 motors (Key specs at 6 V: 75 RPM and 80 mA free-run, 85 oz-in (6.1 kg-cm) and 2.2 A stall.) and build 2 motor drivers like the one attached (one motor driver will control the motors from a side).

    I have created the schematic based on the L298 data sheet and just added the 2 LEDs for visual feedback of the rotation of the motors.

    Will it be ok?

    Thanks

    Sorin
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Do you realize that the L298 will drop in excess of 3.8v across itself when under a 2A load? This leaves only 2.2v at best for your motors. The rest of the power will be dissipated as heat in the L298. Is that acceptable to you?
     
    trimbitassorin likes this.
  3. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,043
    3,807
    Look for a modern MOSFET bridge, by the time you add a heat sink, that big chip for each motor and the extra battery voltage to overcome the drop-out (as mentioned by Sarge above), your robot will be huge, heavy and dead slow.
     
  4. trimbitassorin

    Thread Starter New Member

    Jan 19, 2014
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    0
    No, I didn't know it is so bad and the motors will be probably a lot of time under 2A load. Thank you for pointing this out!
     
  5. trimbitassorin

    Thread Starter New Member

    Jan 19, 2014
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    Can you please suggest one that doesn't require a lot of external components and it is suitable for my motors?

    Thank you!
     
  6. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,797
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    If you don't have a second voltage available (say 12V, able to supply 10mA or so on average) for the switching control of a FET bridge you would need 'logic-level' type FETs.
     
  7. trimbitassorin

    Thread Starter New Member

    Jan 19, 2014
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    0
    I will have only the Arduino Mega (with a 7.2V supply going through a 5V regulator) and supply for motors (probably another 7.2V Li/ion battery pack).
     
  8. tubeguy

    Well-Known Member

    Nov 3, 2012
    1,157
    197
    If you can live with relays to switch direction, a circuit using a single logic-level Mosfet to drive the motor is also possible. :)
    Or can you possibly use a higher voltage battery for the motors?
     
    Last edited: Jan 20, 2014
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