At 06:45 PM 2/18/02 -0600, you wrote:

>As a bonus, it looks like I could use one more pin and
>turn on just one MOSFET to drive the lights with half-wave rectified DC.

Your transformer will not be happy with you doing this.

>I took a quick look at Digikey - 2SK2614 looks like a winner.  50V/20A,
>less than .08 Ohm Rds(on), 4V gate drive and a tad over a buck each.  I
>can drive the gates with RA4 and a pull-up.

Ok, the one IRLZ44N I suggested is about $1 in 100's and is logic level, 41A
0.022-0.025-0.035 ohms depending on 10/5/4V drive level. About $1.70 in
singles. The IRF1010N (72A /55V( is 3.24 in singles and is 0.011 ohms
with 10V drive (not logic level).

Total I^2R or forward conduction losses with 4V/10V drive

Current:                                10A             20A     Cost (qty
1/1000 Digikey)
Triac Q2040J 40A/200V (isolated
case)   10W             20W             7.16/3.97
2SK2614 0.08 ohm at 4V/0.045
10V        16W/9W          64W/36W         2.04/1.05
IRLZ44
0.035/0.022                      7W/4.4W         28W/17.6W       3.46/2.02
IRF1010N 0.011 ohms
(10V)               --/2W           --/8.8W         6.48/3.62

With the possible exception of two IRF1010N's with 10V drive running a <10A
load,
heat sinks required for all these options.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
9/11 United we Stand

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.