$429 Dimmer Switch

Actually, they are a little simpler to design than the old analog beasts, in
that you don't have to do a lot of thermal worst-case analysis. And, the
current limiting is a hell of a lot easier to do.

Watch out, though, that the person who designed it understands RFI and how close
to the noise margin the Loran is. You'd be surprised how many designs have
their switching frequency a submultiple of 100 kHz. and wonder why the loran
(and everything else harmonically related) goes Tango Uniform when the lights
come to life.

Also, you need to understand that switching frequencies on the order of 30 Hz,
90 Hz., 150 Hz., and 9960 Hz. will honk up the avionics also. The hell of it is
that radio manufacturers do a great job of shielding their product against this
sort of RFI, but then run a wire from the dimmer port directly to the lights,
letting any crap on the dimmer wire merrily radiate throughout the radio.

Jim

When my dimmer does
-go, or I add more lighting to the panel, I'll probably opt for one of the
pulse
-width modulated ones (those are much more complicated than the piper pass
-transistor, but they also dissipate very little power).



Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com