Growing up in the 70s and 80s, I'm a sucker for analog meters. There's just something evocative about seeing measurements represented on a physical moving object.
When I realized that you could drive simple analog voltmeters with the PWM output of a microcontroller, I knew immediately what I wanted to do.
- 0-3VDC analog voltmeters. I used 85C1 meters from eBay (Make sure to get voltmeters though, not ammeters.)
- Arduino Pro Micro 3.3v SparkFun
Here's the schematic for wiring the two meters to the Pro Micro:
I took an image of the 85C1 faceplate I had and whipped up a quick-and-dirty scale in GIMP to replace it with. I then printed it on my laser printer and just gued it to the back of the existing faceplate with an Elmer's Glue stick. The result is pretty convincing:
faceplate/ contains the faceplate images I used. Be creative!
This is the source for the Pro Micro firmware. It's very simple. It listens on the serial port for a string starting with A or B followed by a number and sets the PWM output of pins 5 and 6 respectively to the value of the number.
E.g. "A0" will set the PWM output on pin 5 to 0, whereas "A255" will set the PWM output on pin 5 to 255.
This is the client I run in both Windows 10 and Ubuntu Linux. It looks for "krellmeter.ini" in the current directory unless you specify a path to an INI file on the command line. The options are fairly self-explanitory. The "max" parameter for each meter lets you tweak what PWM output makes the meter read "100%".
When the client first starts it sweeps from 0-100, stopping momentarily at 25%, 50%, 75%, and 100%. You can use this to gauge whether you need to increase/decrease "max" for either meter.
Alternatively, connect to the Pro Micro from a terminal program and just send A200 or B200 and see what it reads. Adjust the number up or down to find the top for that particular meter, then update the ini file.
One huge caveat: I'm getting the GPU utlization from the Nvidia "nvidia-smi" client on both platforms. If you don't have an Nvidia GPU (or the Nvidia client library installed) then this won't work for you.
TODO: Make the client more configurable for differing configurations.
Contains pre-compiled binaries for the Linux AMD64 platform and Windows 64-bit platforms. If you use these be sure to grab the krellmeter.ini file from client/ and tailor it for your configuration. (E.g. port=COM3 or similar for Windows.)
I used NSSM to make krellmeter.exe into a service on Windows 10, but any method of running it in the background should work since it doesn't require any special permissions.
Have fun!