> Kevin wrote:
> > I created a small motor control board using a PIC and
> > a SN754410 DNE Motor Driver Chip.
> > I am powering two small motors, and they use about 700ma
> > amps each, when stalled. Each driver of the chip is
> > able to source 1100 ma, so I am in spec. However the
> > chip is getting pretty hot, how do I cool it ? It is a 16
> > pin DIP. I don't have any heat sinks for DIPs. I do have
> > some that screw on to a TO-220 package. Any way to attach
> > them or any other suggestions welcome.
>
> I saw a bunch of other replies, but I think they are answering the wrong
> question.  I don't know what a SN754410 DNE motor driver chip is (no I'm not
> going to look it up, that's your job), but it sounds like the wrong tool or
> maybe its not driven the best way.  Your real problem is an inefficient
> setup.  It's probably better to make it more efficient and therefore cooler
> in the first place than trying to deal with the dissipation of a bad design
> after the fact.
>
> Are the motors DC, brushless DC, something else?  What voltage?  Unless
> you've got a very unusual setup, it shouldn't require much waste heat to
> drive them.  Since motors are inductors and have considerable mechanical
> inertia, they are great candidates for PWM control.  The pass elements are
> always either full on or full off so they dissipate little heat.  Most of
> the losses will come from the voltage drop when on and the transition time
> while switching between states.  Motors work fine with PWM at a few 100 Hz
> so switching transition times should be minimal.  FETs with a few 10s of
> mOhms on resistance are readily available.  Or even bipolars might be fine
> at such low currents.  200mV saturation x 700mA is only 140mW.
>
> In any case we need more information about the motors, the available power
> supply, and how the motors need to be controlled.
>
>
They are small DC Motors 1.5v to 3v.
0.18 - 0.25A at no load 0.70A +- 15% at max effic.
I am using 4AA NiMh batteries to power the board. I am
feeding th SN754410 with the raw voltage. The chip drops 3V
as per the data sheet. Right now I am not using PWM I just
have a logic high on the enable pin for each driver.
The datasheet is here for the SN754410
http://www.pololu.com/products/misc/0024/
but like I said as far as I know I am using the device
correctly.

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