transistors instead of relays

["Cordeiro, Alan" <Alan.Cordeiro@mts.com>]

Mike,

The typical drop across a saturated transistor is 0.3 to 0.35 volts. So
eventually
you may end up with a total drop to the lamps of 0.4 to 0.5 volts. The
typical drop
my older 86 5000q was about 0.7 volts before I added relays, and my newer 91
200q
shows about 0.4 volts drop to the headlights.

The bottom line is that if you are fighting for those last few tenths of a
volt, use
RELAYS, not transistors. (However, if you just want to be able to power 100
watt
lamps, transistors will work, but not as well as relays...)

Alan
 
	But I'm still not happy about the relays. Would it be possible to
switch
	the filaments on and off using a large, heat sinked power transistor
with
	the white and yellow wires providing the "on!" and "off!" signals to
the
	base of the transistor? I know that 30 amp 2N3055's in a TO-3
package can
	be bought for a buck or two, and it strikes me that with a few
resistors
	and an anti-spike diode or two we could have a really reliable
	no-moving-parts system for turning the lights on and off. As an
additional
	benefit, it could be set up so that even when the lights are "off"
there is
	a small bit of power flowing which would greatly reduce the starting
surge
	which is what frequently burns out light bulbs in the first place.

	Any EE's out there in lister-land want to comment?

	Best Regards,

	Mike Arman