1. rajbhutra

    Thread Starter New Member

    Dec 1, 2007
    1
    0
    Hi every one

    I worked on l293 but now i want to work on l298 because l293d is heating on 1 Amp load. can anybody guide me in this regard.
     
  2. mozikluv

    AAC Fanatic!

    Jan 22, 2004
    1,437
    1
    have you followed the recommended heatsink and trace layout from the datasheet for L293?

    i will presume that you have read the L298 datasheet, which part of that you don't understand?

    moz
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    The L293D is rated for 0.6A (600mA) continuous, 1.2A peak (non-repeatable) per channel. No big mystery why it's running hot at 1A.

    Keep in mind that for H-bridges, you need to ensure that both sides of a bridge should not be turned on at the same time, as that creates a dead short across the power supply. While this might seem obvious, what is not obvious is that you may need to wait a short time after turning one side off before turning the other side on due to turn-on and turn-off delays; these times are given in the spec sheets.

    One mistake people make is using an inverter gate (or NAND or NOR gate) to drive one side of an H-bridge; the input of the gate from the control signal and to the high side, the output of the gate to the low side. While it looks like it would work in a schematic, the gate has a propagation delay; when the input is low and a logic 1 is applied, it takes a certain amount of time for the output to transition from a 1 to a 0. During that time, both the input and output are the same, and the power supply is shorted to ground throught the bridge.

    Make sure you read the datasheet for the L298. Pay particular attention to the turn_on and turn_off times, making certain that your driver waits long enough, but not excessively long. Don't forget the protection diodes either, or you'll fry the L298 in short order.

    While the L298 has a 4A peak rating, keep in mind that for continuous DC operation, it's rated at 2A. That's double what you imply what your requirements are, but still, you must follow the datasheet's guidelines for proper heat sinking.

    Remember that copper is roughly twice as effective at conducting heat as aluminum is. Use heat sink compound - but that is in conjunction with ensuring a good, solid mechanical connection to your heat sink.
     
  4. Pete Kirkham

    New Member

    Aug 27, 2010
    1
    0
    If both logic inputs for one side of a L293D are connected to the same value, then both outputs are both connected to either +V or 0V. There is no short across the power supply in this case; there is zero current through the motor as both sides are forced to the same potential.

    This behaviour is illustrated in the data sheet on page 6 ( Fig 9, Bidirectional DC Motor Control) and may be used to stop a motor by inductive braking - in effect it shorts out the motor, not the power supply.

    There would be a short if both transistors on one side of a bridge were turned on; generally if you change the direction of either side you disable the bridge during the transition, though an integrated bridge should have protection against this. Such shorts are nothing to do with whether you use an inverter between the two sides of a bridge.
     
    Last edited: Oct 20, 2010
  5. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,750
    759
    Another Indian Einstein. :eek:

    Dude ..u are barking up the wrong tree

    Definitely not the way for a 1st post
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Gee, this thread died 3 years ago. No point in keeping it going now.
     
  7. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,750
    759
    just couldn't resist myself

    Somebody needs to lock, old threads tht have no point in continuing
     
Loading...