At 02:33 PM 2/17/2000 , Matthew Pollard wrote:
>Radio Shack stocks thermistors and holders.  You could just wire a quick
>mini-circuit that will trigger a LED or just move a meter when the temp
>gets to a bad level. Got it? That is on my to do list... but yeah, sure,
>when ever i have the free time for it!
>
>What do you think?

Sure -- but a thermo switch wouldn't need any electronics at all, just a
buzzer.  Of course the only way to adjust it would be to get a different
one or move it to a cooler/warmer spot on the engine...

An overtemp switch out of a junked microwave oven might be in the right
range, and have mounting hardware too.  Otherwise the thermistor etc would
be easier to find.  There are some analog chips that would have pretty much
everything -- LM3909 for example (right number? -- the one that's meant as
an LED driver for meters.  I'd want an alarm of some sort, most of us
aren't trained pilots who scan the instruments every 20 seconds...

Come to think of it, I put one of these exact switch/buzzer circuits on our
boat -- had a sample lying around that flips at 140 F, which believe it or
not is as hot as you can run a salt-water-cooled engine.  It warns if the
pump impeller wears out, or a chunk of rust blocks the tube btw the head
and the  (water-cooled) exhaust manifold, or if a plastic bag gets sucked
onto the intake screen, or if we heel over too far to port and the inlet
comes out of water...useful little guy.  Regular temp sender cheerfully
ignores all these and lets you wait for the smell of burning paint coming
out of the companionway.  Great little motor -- 30 hp, 310 pounds of cast
iron.  But I digress... <g>.

d
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"