Hi Dumitru,

  You need to swap the drain and source connections on the MOSFET. The 
schematic in your original post has them hooked up backwards. The 7.2V 
flows through the MOSFET's back diode, which is why you aren't able to 
shut the motor off.

  You might want to add your own diode across the motor, with the anode 
connected to the negative terminal and the cathode connected to the 
positive. The MOSFET's diode is supposed to perform the same function, 
but a lot of people add their own just to be safe.

Chris


Dumitru Stama wrote:
> Hello guys
> I have a strange problem when trying to use the attached circuit as a
> small forward-only driver for a DC motor. The Mosfet is an IRF 540 and
> the PIC is 18F452. The pin RC2 in set as output from TRISC and i made
> a small program in C18 to issue a "zero-logic" for one second and then
> "one-logic" (+5v) for another second and so on.
> My problem is that the motor starts turning when the 1 is issued on
> RC2 but instead of stopping when i issue 0 it just turns a bit
> slowly... After 1 second the 1 is sent again on RC2 and the motor
> turns again fast.
> Can you guys help me with a suggestion ? What should i do ?
>
> Dumitru Stama
>
> ------------------------------------------------------------------------
>

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