You can still get moving-needle meters off the shelf if you desire that old school look in one of you projects. However, if you want a more flexible and modern solution, you could use round displays to simulate the same thing, as [mircemk] demonstrates.
At the heart of the build is an ESP32 microcontroller, chosen for its fast clock rate and overall performance. This is key when drawing graphics to a display, as it allows for fast updates and smooth movement — something that can be difficult to achieve on lesser silicon. [mircemk] has the ESP32 reading an audio input and driving a pair of GC9A01 round displays, which are the perfect form factor for aping the looks of a classic round VU meter. The project write-up goes into detail on the code required to simulate the behavior of a real meter, from drawing the graphics to emulating realistic needle movements, including variable sweep rates and damping.
The cool thing about using a screen like this is the flexibility. You can change the dials to a different look — or to an entirely different kind of readout — at will. We’ve seen some of [mircemk]’s projects before, too, like this capable seismometer. Video after the break.
As far as VU meters go, that choppy refresh rate makes it impossible to tell whether it’s actually tracking the level with any accuracy.
Still good for a casual project.
*A PPM enters the chat…
The adafruit library is really not meant for fast smooth animations. I had to write my own display driver library to support two spi displays when I made my digital vu meter.
If it is programmed to display the peak reading of each interval , that’s a good thing. Otherwise you would miss the transient peaks.
It’s sort of like chronometric tachometers on racing cars. They don’t cost ten times as much just because they look cool.
Search for chronometric tachometer videos, it’s fascinating how the mechanical ones work.
Thanks for indicating the LHS display with an L and the RHS display with an R.
This helps avoid any confusion…
Joke appart, nice project and lots of efforts but the final rendering is kind of disappointing : classic VU needle display are far more readable and cooler imho.
Here the display is far too jerky to be pleasant to look at.
Nice idea. Needs a better graphics library, something that can blend pixels, Adafruit is too basic.
The displays can do 240×240, that matches the photo of the real gauges. ESP32 has enough ram to handle a 240x240x16bit buffer. Could pre-blend all the dial positions, but the ESP should have enough cycles to draw a needle on the fly.
Or not old school and use LVGL…. https://www.youtube.com/watch?v=gsTP7zljSBg
Here is the pre-render example, nice…. https://www.youtube.com/watch?v=cZTx7T9uwA4
Or use a real analog meter on top of an e-ink display, as posted right here on Hackaday last year: https://hackaday.com/2024/11/25/e-ink-screen-combined-with-analog-dial-is-epic-win/
Do they make round e-ink displays?
They would look even better if they were real LC displays.
The monochrome models, I mean. The cool ones.