I picked up this neat old volt meter that I'd like to use on my boat.
The guy I got it from told me it came out of a 1920s automobile. I
figured it wouldn't even work, but when I got it home I was surprised to
see that it did work, and I was also surprised how easily the chrome
cleaned up on it. They sure don't make chrome like they used to.

Of course it's a 6 volt meter. Is there a simple circuit I can build
with parts available at Radio Shack enabling me to use this meter with
12 volts?

I don't want to use a store bought DC to DC Converter because that'll
give me a constant 6 volt output with no fluctuations, even if the input
voltage varies.

Floating,
You didn't give us any kind of hint what the meter is for.....

If it is a system indicator (fuel, oil etc) we have one problem.

If it is a voltmeter and you want to read the condition of a 12 volt
system, we have another issue all together.

The First: Go get and find out how to use an LM317 (a regulator that
can be set up from 1.5 to 40v) to supply the instrument.

The Second: If you want it to read 12 full scale (0=0 & 6=12) you need a
resistor that is equal to the internal resistance of the instrument, but
this will not do you much good because 12V systems are really 13.5 to
15V. So you if you get 1.5* the internal resistance now 0=0 and 6=15.

Or you could hunt up a precision zener diode for 9.0V (these are
available but not easy to find) now 0=9 and 6=15. If you can't find teh
zener, you could do this with a LM317. Build a little board to create a
9.0 volt stable reference and use it as the ground for the instrument.

Good Luck Guy
Let us know what you do

Matt Colie

Floating Mind wrote:
I picked up this neat old volt meter that I'd like to use on my boat.
The guy I got it from told me it came out of a 1920s automobile. I
figured it wouldn't even work, but when I got it home I was surprised to
see that it did work, and I was also surprised how easily the chrome
cleaned up on it. They sure don't make chrome like they used to.

Of course it's a 6 volt meter. Is there a simple circuit I can build
with parts available at Radio Shack enabling me to use this meter with
12 volts?

I don't want to use a store bought DC to DC Converter because that'll
give me a constant 6 volt output with no fluctuations, even if the input
voltage varies.


--
target of diversity
victim of affirmative action
refugee from the war on poverty
minimized by political correctness

Sorry about the lack of information in my original post Matt. This is a
volt meter, and all I want to use it for is to monitor the condition of
my battery when there is no charge being applied to it.
This old meter has a screw where I can adjust the full scale landing
position of the needle/pointer, so I don't think I need anything real
complicated to accomplish what I want to do You mentioned a resistor,
and if that will get me close in the ballpark I can fine tune the meter
with that adjustment screw from there.

I see I unintentionally replied with my other username. I'm the OP,
Floating Mind.

On Sat, 10 Mar 2007 10:44:18 -0600, (Sunset
Sam) wrote:

Sorry about the lack of information in my original post Matt. This is a
volt meter, and all I want to use it for is to monitor the condition of
my battery when there is no charge being applied to it.
This old meter has a screw where I can adjust the full scale landing
position of the needle/pointer, so I don't think I need anything real
complicated to accomplish what I want to do You mentioned a resistor,
and if that will get me close in the ballpark I can fine tune the meter
with that adjustment screw from there.

That screwdriver adjustment is really a "fine tuning" adjustment to
allow you to set the meter to read zero with no voltage applied - it
will likely have very little effect on the full-scale reading.

A series resistor equal in value to the internal resistance of the
meter should double all readings - that is, the meter would read 6
volts with 12 volts applied to the resistor/meter combination.


--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
new newsgroup users info : http://vancouver-webpages.com/nnq
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Vancouver Power Squadron: http://vancouver.powersquadron.ca

Thank you Matt & Peter. The resistors worked out. Installed and
working fine. Thanks again for the info.