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Re:



You don't need a relay, a simple power mosfet will do the job.  You need one
that can be driven from logic levels.  It also needs to be capable of
driving an inductive load.  Such mosfets are sometimes referred to as
'rugged'.  The mosfet works as a low side switch to ground, controlled by
the logic level on the gate.  Make sure that the door lock circuit and the
Etrax have a common earth.

There are lots of mosfets to chose from.  The VNP20N07 from SGS-Thomsom
looks suitable, but there will certainly be others.  Have a closer look at
the datasheet.  Or try a google search on 'logic level mosfet inductive
load'.

Dan


> Hello, I wonder if a reader on this mailing list can help me ?
>
> I'm looking for a security and door-entry solution, for internal use in
our
> company.I have a query which will help make my decision as to whether to
go
> for an Axis Developer Board 83 or for another vendor's otherwise-inferior
> 68000 microcontroller variant.
>
> The question is, how might I attach a relay onto a 82/83 development
board,
> connected to the digital i/o port such that it could switch a magnetic
door
> lock on/off, which requires 12V, 250mA ? I presume the GPIO port is 5V
TTL,
> but how much current can it source/sink ?
>
> I'm assuming this has been done by others over the years, and if anyone
> could point me in the direction of a schematic diagram that would be
great.
>
> Kind Regards,
>
> Dr Iain McKay.
>
>
>
>
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