Re: A different fuse.

["Brian K. Michalk" <michalk@awpi.com>]

> solid state device.  It is a positive temperature coefficient (PTC) =
> thermistor.  It has no moving parts, doesn't arc on interruption, acts =
> faster on overload and can be reset in a fraction of a second.  I have =
> attached a circuit diagram that shows the way I protect branch circuits. =
>  Physically, the two LEDs are mounted above a rocker switch.  The green =
> LED lights when the switch is turned on.  In the event of an overload, =
> the PolySwitch turns off causing the green LED to go out and the red =
> flasher LED to flash.  Cycling the switch off and back on will reset the =
> breaker.  Unlike the push button type breakers, you cannot hold this one =
> in and set your plane on fire.

Hmmm, this seems to be what I want.  I've checked in to PTC fuses,
but normally they're used on circuit boards.  Somehow I missed them
in my Digikey catalog.  The specs say that they will trip at 20C
at the minimum rated continuous current.  I'm interested in what the
do at 70C.  Is there an appreciable decrease in mimimum sustained 
current?

BTW, if you want to look at the drawing go to:
<http://www.awpi.com/michalk/fuse.gif>

Would you be willing to test the tripping current required
when ambient is at say, 120F?  You don't need to ask
your wife permission to use the oven, I'm sure she won't mind.

-- 
Brian Michalk  <http://www.awpi.com/michalk>
Life is what you make of it ... never wish you had done something.
Aviator, experimental aircraft builder, motorcyclist, SCUBA diver
musician, home-brewer, entrepenuer and SINGLE!