On Thu, 01 May 2008 03:19:47 -0500, Peter Spikings
wrote:

Hi all,

I'm new at this so some patience might be required, hopefully not
though

About to install a fluid level sensor in my car, it accepts between 5 and
12 V as input so I thought it'd be OK, good thing I realised that was
wrong before wiring it in

So... how do I make / get a cheap regulator to supply it's power? It's
current drain will be tiny. Is it worth using a 5V regulator given that I
have to use one at all? Presumably I'll need a small box and a breadboard
to solder various components into and stuff.

The output of the sensor is going to a piezo buzzer (max draw 10mA) then
to ground, it's a TTL output but I think that's OK.

TIA,

Peter.
What makes you think it won't work without a regulator? If the
specifications specify a wide range of operating voltage it may
already have a regulator or not need one.

Anyhow, if you do need one, a simple three terminal device is all you
need. One connection is 12 volts input, one connection to ground, and
the other one is an output. They work very well but you can never
connect them backwards (that will kill them).

There's a whole series with part numbers like LM7805 for a 5 volt
part, or 7809 for a 9 volt part, and you want to leave 3 volts or so
for input output differential - with 12 in you can't take more than 9
out or it can drop out of regulation.

With no real current drain a little TO-92 case regulator can supply
~100 milliamps while the larger cousins TO-220 can supply 1,000 ma.
You could wire it directly and cast it in epoxy with no circuit board.

http://www.national.com/mpf/LM/LM78M05.html
It is good practice to use caps on the output to compensate for long
wire runs, and there's even a litany of does and don'ts to survive the
rigors of car electrical systems - but I seldom try to make my
regulators bullet proof and they do just fine.

http://www.datasheetcatalog.com/data...0/5/7805.shtml for
the datasheets - search for "application notes" 7805 if you want to
learn more about them.

The nominal 12 volt car is generally acknowledged to be 13.8 when
running.
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