Re: What was that?????

["Jim Lux" <jimlux-at-jpl.nasa.gov> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

> 	I'm holding one in my hand which only has two leads - it was the
> cheapest one I found at Home Depot and is the use I use, in series with
> a 3 ufd high-current capacitor, to excite a GM high-energy spark coil. 
> Works just fine.  By the way, you'll find circuit schematics for such
> devices in typical application notes for SCR/TRIAC/QUADRAC devices.

Typical circuit in a dimmer has 1 resistor, 1 pot, 1 cap, 1 active device,
and maybe, an inductor as a snubber. These are, after all, a very price
sensitive product, and saving a half cent in material cost is important
(because Home Depot type places only stock the cheapest one).  Typical
parts cost to retail price ratio is 1:10. Lutron is probably the biggest
mfr of dimmers, and has the best cheap designs.  If you pay $40 apiece, you
get better designs, but Lutron apparently has the <$10 market locked up..
They buy more components, etc. and get the best prices.    This is a case
where cheaper is actually better.... at least among the class of product..

Teccor being the big MFR for the active devices (a quadrac, typically,
effectively a diac in the gate of a triac).  In general, for biggish AC
loads, particularly for inductive loads, back to back SCRs work better than
a triac, but for running an ignition coil, you probably don't care if it
self triggers from dv/dt...