"Andrew Cockburn" wrote in message
-service-com...
Very nice !

One question ... on PowerIndicator.jpg what is vr1 for ? I assume it is
preset for calibration, so do you just set that so the led's read full
just after a charge ?

As I said, the circuit was is a modified version of one that I found on the
net. Here's some more details about the circuit itself....

Connect an input voltage of 12.65 volt between the positive and negative
poles and adjust the 10K trimmer potentiometer (That's vr1)
until Led 10 lights up. Lower the voltage and in sequence all other Led's
will light up. Check that Led 1 lights up
at approximately 11.89 volts.


At 12.65 volt and higher the battery is fully charged, and at 11.89 is
considered 'empty'.
The green Led's indicate that the battery capacity is more than 50%, the
yellow Led's indicate a capacity of 30% - 50%
and the red Led's less that 30%.

The original circuit for this was on
http://www.uoguelph.ca/~antoon/circ/batmon12.htm so no pont re-inventing
the wheel. The modifiction that I made to it was to add the 5K6 resister
to Pin1 and V+ This then uses up some current that is drawn through this
pin whenever the signal is about the voltage required to light LED2 and
above. Basically it allows the circuit to work in both dot and bar mode,
better than the original circuit. I'm not sure, but I think this may not be
required if one of those bar graph displays is used. I decided that I
wanted 10 3mm LED's to spread the scale out a bit.


Also, if I could persuade you to share your PCB design when you are
ready that would be great !

Here's the link to my PCB Layout.

http://www.cjdawson76.btinternet.co....dicatorPCB.jpg

Print it so that the outline is 100mm * 75mm. This will give the correct
proportions on the print. This layout is meant to be printed onto
transparency for Photo-etching.

To complete the job, lay this ink side up onto a glass sheet. Place the
photo-sensetive side onto the transparency, so that the ink touchs the photo
film. This will ensure the best possible image. I won't go into details
about photo etching, for anyone not familer with photo-etch techniques,
that's why it appears to be reversed.

If you use the circuit diagram
http://www.cjdawson76.btinternet.co....rIndicator.jpg you
should be able to work out where all the components are supposed to end up.


As per your and Chris' advice, I'll get the car-starter to keep me
going, then I can spend some time puttting together the whole power
supply, and dew heater. What kind of box are you planning on using ? I
was thinking of using a largish plastic toolbox as I am crap at woodwork
....

A Car starter will keep you going to quite a while. You might even decide
not to try to *improve* on it. Another alternative that I thought about was
to have the Dewheater and scope power in one box, then a lead that connects
to the Jumpstarter.

As for the box, I'm also crap a woodwork, but I just can't seem to find a
box that even comes close to fitting my needs. So I've decided to bite the
bullet and build one from wood. It's taking alot of thinking about, but
it'll be worth it in the end.

Regards

Colin Dawson
www.cjdawson.com