On 19 Oct 2005 11:20:01 -0700, "iflycozy"
wrote:

Question to you electrical designer gurus:

Here is what I would like to do and Jim Wier suggested that I post this
here. I want an indicator on my Cozy homebuilt airplane to show me
that my heated pitot is actually working when I turn on the switch on
the instrument panel. So, the light will go out (with the switch still
in the on position) if the heated pitot stops working for some reasons
(but not because it tripped the circuit breaker). So, how can I build
such a device or circuit? I would appreciate specific parts or
identification of parts as I am an amateur. This is a 12 volt DC
system and the heating element draws 7 amps. I know I can not use a
LED in series because it would blow the milli-second I turned the unit
on. I know I can't use a light or lamp in parallel because it would
not indicate if the heated pitot was on or off. So that is my dilemma.
Please help.

Find one of those out door thermometers with a remote read out. Some
of the older ones had a meter. The newer ones have a battery powered
digital read out which could probably be adapted to the plane's
electrical system, but you wanted simple.

Just drill s small hole into the pitot tube metal where is it thick,
preferably from the inside of the mount. (stay away from the heaters
and the actual tube) Put a little heat sink compound in the hole,
stick the remote sensor in, clamp it in place and run the wires to the
inside where they hook to the sensor. Neat, easy, simple.

As a side note, you don't need accuracy. Fire up see what it reads.
Go flying and see what it reads. It won't be near as hot on cold day
and even less so in rain, but I doubt you'll be flying the cozy in the
rain. Put a sticker or just a piece of tape above, below, or beside
the read out with what you'd expect to see for normal readings.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

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Roger