ECT and voltage divider help?

[Ludis Langens]

Daniel Houlton wrote:
> 
> They have brief descriptions, but
> none indicate that they'd be used for sensing a voltage level without
> changing that level.  Is this just a basic non-inverting amplifier?

To buffer the signal, use a "Voltage Follower".  Connect the input
signal to the + input.  Connect the - input to the op-amp output.

> Why is a small gain a convenience?  What's it do?

You may find it easier to work with a higher voltage in the rest of the circuit.

> I saw the comparator circuit too.  It's just an op-amp without a
> gain feedback right?

Yup.

> Op-amps need + and - voltage.  How would I get the - voltage?  I can
> get 14.7V from the battery, but how do I get it to be negative as
> well?

Simple, buy an op-amp that doesn't need a negative voltage.

> Also, how would I get the .6V reference that I want?  Just tap into
> the 14.7V power and use a resistor or pot to drop it all the way to
> .6V?  That sounds the easiest.

Regulate the 14.7 to something lower before using a voltage divider to
make your reference.  Does you car's computer have a 5 volt output (for
a TPS or MAP)?  You can use that as a reference.  In fact, that is
probably the best reference you can get because it should track the
voltage that the ECT pullup resistor is connected to.

-- 
Ludis Langens                               ludis (at) cruzers (dot) com
Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/
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