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My L298 Become hot.... — Parallax Forums

My L298 Become hot....

pusinkpusink Posts: 68
edited 2012-09-02 12:16 in General Discussion
I'm using L298 to control 2 dc motor (tamiya), but my l298 become hot. Any tips to reduce or eliminate the problem??
thank you.

Comments

  • ElectricAyeElectricAye Posts: 4,561
    edited 2011-07-19 07:43
    pusink wrote: »
    I'm using L298 to control 2 dc motor (tamiya), but my l298 become hot. Any tips to reduce or eliminate the problem??
    thank you.

    The chip getting warm might be normal for your application. Are you using a chip version of the L298 that has a tab for a heat sink? Some of these have a heat sink tab for a reason.

    For example, look at the heat sink screwed to the L298 in this product:

    http://www.sparkfun.com/products/9670
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2011-07-19 07:43
    Tamiya motors are rated for 3v operation, and draw excessive current at 4.5 to 6 volts, the minimum that the L298 is designed to provide. You need to replace the motors. Assuming the motors in the Tamiya gearboxes are the FA-130 size, you can replace them with these:

    http://www.pololu.com/catalog/product/1117

    -- Gordon
  • RavenkallenRavenkallen Posts: 1,057
    edited 2011-07-19 08:07
    Or you could throw a couple of these on the power supply input. The Diode should limit the current to a amp(Or two if you attach two in parallel). It is a quick fix, but i am not sure if it will go the distance..
    http://www.sparkfun.com/products/8589


    PS.. You will also have a slightly less output voltage due to the voltage drop of the diode.
  • davejamesdavejames Posts: 4,047
    edited 2011-07-19 12:09
    Ravenkallen wrote: »
    Or you could throw a couple of these on the power supply input. The Diode should limit the current to a amp...

    Rav - how so?
  • Spiral_72Spiral_72 Posts: 791
    edited 2011-07-19 14:28
    Ravenkallen wrote: »
    Or you could throw a couple of these on the power supply input. The Diode should limit the current to a amp(Or two if you attach two in parallel). It is a quick fix, but i am not sure if it will go the distance..
    http://www.sparkfun.com/products/8589


    PS.. You will also have a slightly less output voltage due to the voltage drop of the diode.

    A resistor would do what you said.... not a diode. Granted, a very large resistor, but it would work..... A diode would voltage drop and flow all the current until it smokes at >1A (theoretically)

    Isn't a L298 a chopper drive?? If so, you have your current sense set wrong (I think)... otherwise, there ARE chopper IC's available that would more efficiently control power. If you can't find one to handle that low a voltage, there are chopper circuits available all over the net. CNC world, and the like document them.


    Edit: Uh, that's CNC "ZONE" not world.
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2011-07-19 16:20
    If a guy wants to "lose" two volts that are causing his L298 to heat up, then he can do so with diodes - if they're placed in series with the motor (see attached.)

    I'm not "for it", I'm not advocating, but it can be done.

    ( + the heatsinking, too.)
    bridgeless2V.JPG
    339 x 248 - 11K
  • ercoerco Posts: 20,261
    edited 2011-07-19 16:29
    Agreed, diodes are better for dropping a few volts than resistors or a rheostat. Their voltage drop is more constant than a series resistor. A motor with a series resistor loses torque more quickly as the RPM drops, and its stall torque is drastically reduced.
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2011-07-19 18:41
    Dropping the voltage isn't going to help much. Even at 3 volts the original FA-130 motors included in the Tamiya kits will pull over 2 amps at stall. That's what the L298 is rated for per channel, with a heatsink.

    Granted, hopefully the motors won't be stalled often or for long, but under nominal load you could reasonably expect a draw of 1.5 amps @ 3v, and that'll make an L298 pretty hot.

    Like I said, the best solution is to spend a couple of bucks and buy replacement motors that consume no more than 0.8A at stall, and operate at 6-12 volts. Considering the L298 wants to see no less than 2.3v for its input HIGH voltage, and the motor supply should be no less than 2.5v over that, a 6+ volt supply for the motors is more ideal.

    -- Gordon
  • RavenkallenRavenkallen Posts: 1,057
    edited 2011-07-19 19:35
    Oppps. Looks like i gave some bad advice:( I also have a L298 on a Rover 5 platform and mine gets very HOT!!. So i tried putting a diode or two(attached to the + power supply pin, not the logic input) and it brought the heat down some. But the diode got really hot and the L298 was still pretty hot... My understanding of a diode, is that the diode will allow any current to pass through it to the load, JUST as long as it doesn't go over its max current rating. If you operate it at a higher voltage it will also increase the amount of heat(Power) that the diode is consuming? If the total power used is over it's maximum wattage rating, the diode will start getting hot and potentially become unstable... SO if a diodes maximum power rating is 3 Watts(like the one listed above), theoretically it could supply 1 Amp of current @ 3 volts right before getting hot right? Or 500 mA's @ 6 volts?
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-07-19 20:43
    There's nothing wrong with powering a motor from more than its rated voltage, as long as you can PWM it. The motor's coils, being inductors will average out the current. A high drive voltage is even more effective if you can monitor the current and adjust the PWM duty cycle accordingly.

    -Phil
  • Mark_TMark_T Posts: 1,981
    edited 2011-07-20 03:57
    pusink wrote: »
    I'm using L298 to control 2 dc motor (tamiya), but my l298 become hot. Any tips to reduce or eliminate the problem??
    thank you.

    Is it a problem - or in other words how hot and is it dissipating more power than its designed for (given the heatsinking present)? The package can dissipate 25W with efficient heatsinking which is more than its transistors are rated to generate.

    Note that the L298 is not efficient at low voltages as its output Darlingtons together drop 2.5V (3.3V worst case) at 1A and 3.7V (5V worst case) at 2A. I wouldn't recommend it for less that 24V supply for this reason. Its certainly not designed for 6V supply.

    It may be the case that you need a better motor controller with MOSFET H-bridges.
  • PJAllenPJAllen Banned Posts: 5,065
    edited 2011-07-20 05:30
    Higher than rated voltage as long as it's PWM'd?
    Really,...
    I'm sorry, but what's the top end on that with a 3V motor? 24V, 50V, 100V?
    [You know that if I don't insist on the logical extreme in the theoretical that somebody will "mis-read" and expect the logical extreme in the physical.]

    This Mabuchi over-volts thing was addressed recently in the following thread/subject -- http://forums.parallax.com/showthread.php?132762-Mabuchi-Motors-voltage-greater-than-3v&highlight=mabuchi

    There's on off-site link to a report of Mabuchi over-volts therein -- http://www.pololu.com/docs/0J11/all
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-07-20 07:42
    PJ Allen wrote:
    I'm sorry, but what's the top end on that with a 3V motor? 24V, 50V, 100V?
    'Depends on where arcing begins to occur. :)

    -Phil
  • ssupun90ssupun90 Posts: 1
    edited 2012-09-01 10:47
    your motor may take more than 2A current,so that will be a major reason for your l298 to become hot.Attach a reasonable size to the IC.
    If it is still hot,look at the data sheet of your motor and check how much its' stall current.
    You may feel if its stall current is more than 2A,it cannot be driven by l298 IC.You will be able to drive the motor by connecting channel A with channel B.
    Here is the link to my design
    http://code.google.com/p/fritzing/issues/detail?id=875
  • ercoerco Posts: 20,261
    edited 2012-09-01 10:59
    Good call, ssupun90. Sadly, puskink's post is a year old already; I suspect that particular L298 may be toast by now! :)
  • GadgetmanGadgetman Posts: 2,436
    edited 2012-09-02 12:16
    Also, theoriginal poster never specified which model motorhe used, or the voltage he fed it...

    Sure, the Tamiya plastic kits often comes with a sad 3V motor, but they also have such beasties as the 540 series.
    Proper voltage range: 7.2-8.4V
    RPM at best efficiency: 14500rpm(7.2V)
    Toque at best efficiency: 255g.cm(7.2V)
    Current consumption at best efficiency: 7.9A(7.2V)
    http://www.rcmart.com/tamiya-53689-540j-motor-p-16068.html?cPath=1560_948

    any bets as to how long a L298 would last?
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