10 September 2017

Redraw Analog Meter scale with Inkscape

A dual-needle clock.
Guess what? I've had a challenging idea of a (clock) project, and it has suddenly become top priority. Because of the new challenge.

I want to make a clock using a dual needle analog meter. Ideally an SWR meter would be converted into this analog clock. Electronically speaking, with an Arduino and a couple of PWM outputs, interfacing is simple. A few lines of code and you're done.

The challenge lies in redrawing meter scales. The easy part requires to scan the original panel detached from the meter, and then it is all a learning expeerience.

Once you compute that the needle moves over an angle of 60 degrees with a radius of about 48 mm, both scales have to be drawn with proper marks: one every hour or five minutes.

Old fashioned way: draw it by hand. Fun and relaxing, but not too professional looking.

Test printout.
Do it on the computer: how? A drawing software is needed. Possibly free. And with layers so that the original scan can be used as a reference. Something in the back of my mind suggests that I need a vector graphic software and the search engine response is: Inkscape. It runs on Windows, Mac and Linux.
Not willing to install software for a one-time project on "main" home computers, I turn to the 10-year old HP Pavillon laptop on which I installed Ubuntu Linux 12.04. Once I head to the package manager and search for Inkspace I am welcomed with a warm "Already Installed" message.
The Internet is full of tutorials, but Inkscape itself is well documented too. In two hours I manage to redraw my scales the way I want and I even get the size right at the first printout. All for free.
The original scale (on plastic) vs. redrawn.
By the way, the laptop is a Core2Duo with 1.5 GB RAM and 120 GB HDD (dv6236ea Frankenstein). It runs LibreOffice just right. Firefox surfs the Internet without a problem and I can watch HD videos full screen off YouTube because the NVIDIA graphic card is fully supported. Arduino IDE works too and ... Dropbox (which does not work anymore on WinXP)!