> Dear Piclisters,
>
> I have yet another question for you. I am still a newbie in electronics
> and PIC's and I feel a little bit shamed that I only come to ask
> questions on this list and rarely know how to answer to other questions,
> but hope that someday I will be able to be more active here.

        Please, do NOT feel ashamed. EVERYONE here was, at one time, a "newbie",
and did what you do (it's called lurking), in fact many PICLIST members
still mostly lurk, and there is NOTHING wrong with that, it's why the list
is here IMHO.

> My questions is: I want to drive a siren from a microcontroller pin. The
> siren is an alarm one, and consumes 12V and 3A at maximum. Which would
> be the best way to control it (on/off) ? A power MOSFET, a triac maybe,
> a relay ?
> Thank you for your answers.

        Well the "best" way depends on you and your situation. IMHO the EASIEST way
is a relay, a simple jelly bean transistor (say a 2N2222 or 2N2904) driving
a relay. The reason I say it's "easiest" is it completely electrically
isolates you from a devices that may do very ugly things on it's power lines
(sirens can be very inductive causing huge power spikes on the lines)

        The relay solution however isn't the most elegant, uses more space then it
has to and wastes power. The most efficient way would be a MOSFET, use a
logic level MOSFET that can handle at least 5A (I'd say get one that does
10A, the siren is speced for 3A but I'm willing to bet it's surge current is
higher). Check out the company International Rectifier for good parts, their
IRFZ line should be what your looking for, if memory serves.

        TTYL

----------------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/

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