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[DPRG] motor driver overheating

Subject: [DPRG] motor driver overheating
From: Kipton Moravec kip at kdream.com
Date: Sun Oct 15 10:39:02 CDT 2000

Thermal shutdown is when the amount of current flowing through the device is
great enough to heat up the device faster than the housing can dissipate it.
Once it hits a temperature that is near what could damage it, it shuts down
so it does not blow out.

If the controller is switching into thermal shutdown, you will know it
because the device will burn your fingers if you touch it.

You can prevent this a couple of ways.

1.  If you do not turn it on, it won't get hot. :)

2. There is more power consumed in the switching than in the on or off
position.  You could try to slow down the PWM rate.

3. If you are running in design parameters, then get a heat sink.  The
devices are designed to be used with a heat sink, and you probably can not
get much performance without one.  If it is taking 30 seconds to heat up,
enough to shut down, you probably do not need a huge heat sink.  However, if
you do not know how to do the thermal calculations, error on the big side.

The heat needs to be dissipated to the air. Things to remember.

The more surface area the easier to transfer the heat to air. (That is why
most heat sinks have ribs. )

The thicker the metal, the less resistance it has to conducting heat. More
important if it has to travel a distance.

The more air that flows across the device the more heat is dissipated. (In
other words, use a fan.))

Thermal grease lowers the heat transfer resistance between the device and
heat sink. (In other words, use it)


----- Original Message -----
>From: "Matt Middleton" <ussf at pentagon.navy.org>
To: <dprglist at dprg.org>
Sent: Saturday, October 14, 2000 9:16 PM
Subject: [DPRG] motor driver overheating

> I have a TI SN754410 motor driver, which is essentially the same thing as
> the l293d.  I am running two small mabuchi model motors on a 4.8 V NiCd
> Battery.  After 30s - 1 minute, the motors begin to lose power, and I
> believe that it is the controller switching into thermal shutdown mode.
> Other than getting a heatsink, I don't really know what to do to prevent
> this from happening, so any suggestions that someone might have is
> I would sure appreciate them.
> Thanks,
> Matt Middleton
> _______________________________________________
> DPRGlist mailing list
> DPRGlist at dprg.org
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