T i m wrote:
On Thu, 21 Sep 2017 21:41:44 -0700, mike wrote:

On 9/21/2017 8:13 PM, wrote:

End rant.

He's making a one off for use at home, not commissioning a new
design of military hardware.


The task is the same no matter who the customer.

It can and maybe should be, in an ideal world. I say that because I
hate having to deal with 'fools who rush in' or those expecting me to
make technical / choice decisions on their behalf (like getting them
some 'size 10, brown, lace up leather shoes'). ;-(

The more steps you skip, the more problems you have.

'May have'.

The more you think like a project manager, the better
managed your home projects.

Agreed. I like to understand as much about something as I can.
However, my ability to do so, time available to do so and the
pertinence of doing so don't always allow me to do so or to do so to
the level I would like. Sometimes you just have to get stuck in. ;-)

Once you acquire the habit, you'll find that it adds
little to the time in the beginning and greatly simplifies
the end.

Agreed 100%.

And it wastes far less time for rocket scientists in residence.

Quite ... however, this is a 'discussion' group and so does have an
element of that, along with the hard science / fact stuff.

Part of the 'human' bit is not making a post (especially the initial
one) too long (I fail most of the time) as it will put people off
reading it and if there were any further points that need refining
they could be done with a simple Q&A.

e.g. I initially outlined the fairly close detail at a level relevant
to my needs and understanding (IMHO anyway). I didn't expand on what I
was going to actually use it for because it didn't really matter to
the question. I left it open to the reader to ask any supplementary
questions as they felt relevant. ;-)

Cheers, T i m

Wow, what a long thread about such a simple problem. Here's a web page
describing exactly the circuit you need for an expanded scale voltmeter
(http://sound.whsites.net/articles/meters.htm). Scroll down to Apragraph
5.0 to get to the expanded voltmeter discussion. It uses a 1ma movement for
the discussion, so you'll have to calculate the resistor values to fit your
meter. It uses a 10V zener and one more resistor.

Another method that I've used in the past to make an expanded scale meter is
to suppress the mechanical zero. You still have (in your case) a 0-15V
meter, but the needle doesn't get up to the "0" mark until 10V is felt
across the circuit. After that, the meter responds normally, up to 15V full
scale. So,with this approach, you don't need any extra circuitry to make an
expanded scale meter.
This means that you'll have to open the meter and (CAREFULLY!!) move the
mechanical zero tang. First, apply 10V to the circuit. Then, turn the
mechanical zero tang so that the pointer goes down to the "0" mark.
Reassemble the meter movement, and you're all done.

To make this approach work, your meter movement must have enough mechanical
adjustment range to suppress the pointer enough so that it needs 10V across
the circuit to make the meter read "0" V. Typically, D'Arsonval movements
have about 20-30% range on the mechancial zero adjustment, so yours might be
a long stretch for this method. Never know till you try!!
Dave M