Use a small PIC that has an ADC (IIRC the 12F675 and 12F1501 have 10-bit=20
A/D's), an external reference voltage and a single bi-color LED. =20
Green=3Dall good, red =3D below normal, flashing red =3D critically low, or=
=20
perhaps over normal, etc.

Cheers,
-Neil.


On 7/22/2012 6:56 PM, Carl Denk wrote:
> Thanks for the thought, but I'm trying to keep the interior clean of
> add-ons, and make it permanent. On the Fords we have the cigarette
> lighter power is on all the time. If I was going with a display, it
> would have to be less than 1" square footprint to fit the available
> space in a convenient eye sight location. Others drive the vehicle that
> are not as technically orientated as me, so it has to be simple with no
> action from the driver when starting or stopping a trip, and only react
> to a warning light with possibly reading the manual (would make an
> appropriate entry there) or calling home.
>
> Another approach would be to tie to the OBDII, request the voltage and
> display it or set the warning when needed, but that's a lot more work,
> and more money.
>
> On 7/22/2012 6:17 PM, Marcel Duchamp wrote:
>> A friend bought a gadget at a national auto parts chain store (Kragen or
>> whatever), that is a cigarette lighter plug with a 2.5 digit LED 7
>> segment display.  The lighter power is switched so it doesn't run all
>> the time.  It might do what you want for reading battery system voltage.
>>
>>
>> On 7/22/2012 11:10 AM, Carl Denk wrote:
>>
>>> I'm thinking of adding a low voltage warning LED.


--=20
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