Dale Botkin wrote...

>And it uses very little board space, very little power (not that it's a =
big
>issue), can easily handle the current of the string of lamps, has no =
moving
>parts, and will cost me less (from my supplier) than a good quality =
relay to
>do the same job - with better control.  Not to mention the geek =
factor...  8-)

One added thought, here:

If you want soft-start for those yard lights, one easy way to obtain it
would be to put an RC low pass filter between the MOSFET gates and the
PIC pin doing the control; something with a time constant of a few
hundred milliseconds or so.

As the gate voltage is ramped up past Vth, the MOSFETs start conducting
but initially act as current limiters, giving a true soft-start that
absolutely prevents the cold filaments from drawing excessive current.

During the soft-start interval the MOSFETs are going to be dissipating
considerable power, so it would probably be best not to make the
interval any longer than necessary so they don't overheat.

Of course, soft-start controlled by a ramped PWM would have a higher
"geek factor" than just a simple RC, wouldn't it...

Dave

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