13 VDC switch

A. Maxim is very poor on production delivery.

B. Joe Sixpack in East Undershirt Ohio can't go down to the corner Maxim
store and buy onesie-twosies on Sunday afternoon.

C. One milliampere out of a 25 amp-hour battery will run the battery down
in 25,000 hours (1040 days, or a little less than 3 years). If you don't
fly your airplane but once in 3 years, that's not my problem.

D. Why would you use an unreliable electromechanical device like a relay
when a FET is half the price and a thousand times more reliable?

Jim




"Rob Turk" wrote in message
news:Y7_gg.1536$YI3.268@amstwist00...
"RST Engineering" wrote in message
...
What do you want the cutoff voltage to be? Personally, I'd pick 13.0
volts, but it is child's play to do any voltage you want.

There will be about a milliampere of quiescent current for the sensor
that will still be on-line when the output shuts off.

Jim


One-chip solutions designed for this purpose that can detect both
undervoltage and overvoltage are available from several vendors, such as
Maxim.
Example: http://pdfserv.maxim-ic.com/en/ds/MAX6457-MAX6460.pdf

These offer very low quiescent current when off (couple of uA). The output
can be used to activate a relay (maybe needs an extra transistor). I think
you can request free samples.

Rob

"RST Engineering" wrote in message
...
A. Maxim is very poor on production delivery.

That's not been my experience, but maybe I've just been lucky. Also, when
they offer samples then the chips are available at least in sample
quantities. That may not mean much if you want to order 100.000 of them, but
for us one-off builders this is fine.

Besides, Maxim was just one example. Linear Technologies has similar chips
and similar sample programs.


B. Joe Sixpack in East Undershirt Ohio can't go down to the corner Maxim
store and buy onesie-twosies on Sunday afternoon.

The samples ship worldwide. If I can get them easily in Hoevelaken, The
Netherlands, Europe then I'm sure they'll ship to East Undershirt Ohio as
well.


C. One milliampere out of a 25 amp-hour battery will run the battery down
in 25,000 hours (1040 days, or a little less than 3 years). If you don't
fly your airplane but once in 3 years, that's not my problem.

Agree, and if you leave your plane for 3 years without flying I'm sure there
will be other issues to worry about..

D. Why would you use an unreliable electromechanical device like a relay
when a FET is half the price and a thousand times more reliable?

Agree again, it's whatever makes you feel happy. I've had luck with either
device. Automotive relays seem pretty reliable, and so are FET's.


Jim

Rob