Homebrew PCBs

On Thu, Apr 29, 2010 at 10:36 AM, Richard Spelling
<rls@...>wrote:

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> Went to bed tired and annoyed I couldn't easily find a slower gear motor
> for the laminator.
>
> Dreamed about building a magical speed controller that would let me run
> the existing motor infinitely slow.
>
> Realized I could use "temporal kinetic and thermal stabilization" since
> it's a worm gear motor.
>
> I.E., I build a standard PWM controller but set the frequency real
> sloowwwwww.
>
> Imagine having the speed turned down real low. Along comes a pulse. The
> motor spins up and turns the worm screw a revolution or two, then spins
> down. The board advances a fraction of an inch. An in-determinant amount
> of time later, along comes another pulse.
>
> Yes, it's "jogging" the board forward and not continuous motion, but
> between jogs it sits between the rollers long enough for the heat to
> transfer through the paper.
>
> I'm thinking about 10Hz.
>
> Whatcha think? Just another crazy idear from Richard?
>
> Now I just need to build the board.
>
> Wait a second, I need my laminator to build the board to fix the
> laminator!
>
Richard,

PWM control of motors works very well - with a reasonable pulse frequency,
you're for all effective purposes implementing a steady, consistent slow
pace.

I've had good luck driving simple DC motors at extremely low speeds (10-20
seconds per revolution) by connecting the PWM outputs of my Arduino (AVR
microcontroller) to the motor via an SN754410NE compatible H-bridge driver.
Since you don't need to do reversal, your implementation should be even
simpler.

The Arduino uses a fixed 490Hz PWM frequency, with a variable duty cycle.  I
haven't done any experimentation with different frequencies.

-Andrew


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