Running a Simple motor

Started by Gavin April 28, 2006
Hey All

I'm using the MC9S12NE64, I've written a simple code so that when a
switch is pressed it will turn a motor on for 1/2 second. I'm using
the 3.3v from the NE64 to power everything.

When testing with a LED everything works as it should. The light
switched on for 1/2 seconds. But when I replace it with the motor
nothing happens.

Can someone please help me and tell me why the motor isn't switching
on.

Thanks
Gavin
> -----Original Message-----
> From: 6... [mailto:6...]
> On Behalf Of Gavin
> Sent: Friday, April 28, 2006 12:53 PM
> To: 6...
> Subject: [68HC12] Running a Simple motor
>
> Hey All
>
> I'm using the MC9S12NE64, I've written a simple code so that when a
> switch is pressed it will turn a motor on for 1/2 second. I'm using
> the 3.3v from the NE64 to power everything.
>
> When testing with a LED everything works as it should. The light
> switched on for 1/2 seconds. But when I replace it with the motor
> nothing happens.
>
> Can someone please help me and tell me why the motor isn't switching
> on.
>
> Thanks
> Gavin

The motor is probably drawing too much current, dropping the motor
supply voltage so it does not start.

Emmett Redd Ph.D. mailto:E...@missouristate.edu
Associate Professor (417)836-5221
Department of Physics, Astronomy, and Materials Science
Missouri State University Fax (417)836-6226
901 SOUTH NATIONAL Dept (417)836-5131
SPRINGFIELD, MO 65897 USA

"When I was a child, I spake as a child, I understood as a child, I
thought as a child: but when I became a man, I put away childish
things," like being too embarrassed to ask questions which my peers
might think as stupid.
How large (starting current requirement) is this motor ?

Switching a motor is likely not good for the life of your processor. The motor holds a lot of "trapped" flux and when switched off will generate very high voltages as necessary to keep the current flowing in the way of all inductors. The spikes will destroy your processor.

You need to operate the motor from a separate supply and optically isolate the control. If one leg of the motor is grounded you need to make sure the layout does not permit motor ground current to flow through traces on the digital circuit board.The motor should have a reverse biased 1N4007 diode and a .1uf ceramic capacitor across its terminals to "snub" switching transients.
----- Original Message -----
From: Gavin
To: 6...
Sent: Friday, April 28, 2006 10:53 AM
Subject: [68HC12] Running a Simple motor
Hey All

I'm using the MC9S12NE64, I've written a simple code so that when a
switch is pressed it will turn a motor on for 1/2 second. I'm using
the 3.3v from the NE64 to power everything.

When testing with a LED everything works as it should. The light
switched on for 1/2 seconds. But when I replace it with the motor
nothing happens.

Can someone please help me and tell me why the motor isn't switching
on.

Thanks
Gavin

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