"Bobby" wrote in message
...

"John Fields" wrote in message
...
On Sun, 03 Feb 2008 08:37:57 GMT, "Bobby" wrote:

I need advise on the following:

The device I am making will use this FET as an output. The device will
operate in the range 12 - 24 volts, depending on the users requirement
to
illuminate a few light bulbs.

The FET I want to use can handle up to 16 amps at a max of 100v.

I want to suggest the recommended operating current not exceed 1 amp. as
the
FET heats up considerably over 1 amp, and due to space restrictions a
heatsink is not possible.

At 24 volts that would be 24 watts, and at 12 volts that would be 12
watts.

---
I missed it earlier, but that's not necessarily true since the power
being dissipated will depend on the voltage being dropped across the
MOSFET and the current through it.

What does your circuit look like?

Hi John,

The circuit is simple, goes like this:
1) 12/24V into a 78LS05 supplying a PIC10F202.
2) GPIO,0 connected to gate of FET via 100ohm
3) GPIO,1,2,3 used as inputs to govern output speed, style and run/pause
4) The 12/24 volts (+) as common output with return cct into FET.
Thats it.

The user might connect 12 or 24 volt lamps to the output terminals (FET).
Due to size restrictions the FET cannot be heatsinked therefore 1 amp is
optimum maximum before any significant heating occurs.

If I could supply the DC power pack with the unit that would help,
however
knowing end users as I do they would soon figure out that they could
connect
a heavier power supply (auto battery!!).

Something just occured to me, I wonder if there exists a self resetting
fuse
at a reasonable price???


I use a sensitive circuit breaker on my power supply, this is my protection
because I overloaded my circuit many hundreds times for testing hi-power
circuits etc.. It never fails me.