Analog dials used to be a pretty common way of displaying information on test equipment and in industrial applications. They fell out of favor as more advanced display technologies became cheaper. However, if you combine an analog dial with a modern e-ink display, it turns out you get something truly fantastic indeed.
This build comes to us from [Arne]. The concept is simple—get an e-ink display, and draw a dial on it using whatever graphics and scale you choose. Then, put it behind a traditional coil-driven analog dial in place of the more traditional paper scale. Now, you have an analog dial that can display any quantity you desire. Just update the screen to display a different scale as needed. Meanwhile, if you don’t need to change the display, the e-ink display will draw zero power and still display the same thing.
[Arne] explains how it all works in the writeup. It’s basically a LilyGo T5 ESP32 board with an e-ink screen attached, and it’s combined with a MF-110A multimeter. It’s super easy to buy that stuff and start tinkering with the concept yourself. [Arne] uses it with Home Assistant, which is as good an idea as any.
You get all the benefits of a redrawable display, with the wonderful visual tactility of a real analog dial. It’s a build that smashes old and new together in the best way possible. It doesn’t heart that [Arne] chose a great retro font for the dial, either. Applause all around!
Every now and then, something will show up here that makes you say, “why didn’t I think of that?”
This is one of those times.
yep this is bajootiful
Within a second of seeing the title then the picture, my brain said, “now that is cool”.
Thank goodness this is only a home automation display and not a real pocket meter. It’d be super dangerous if it was. Dangerous because if the unit shows 0v, maybe the circuit is really safe to touch, or maybe the meter powered off and won’t respond even if there’s voltage on its terminals.
A true analog meter can’t have that behavior — it’s powered by the circuit — so users know to trust it. They should not trust this.
A normal digital LCD meter can’t have that behavior — when it’s powered off, the display blanks — so users can trust it. They should not trust this.
So, this is cute in its intended purpose, an informative wall decoration, and if the display hasn’t updated in a suspiciously long time you can go get the information by some other means. But I hope nobody’s dumb enough to copy this idea into the one next to it in the photo, the actual multimeter.
Thank goodness there are no high explosives in this device.
It’d be super dangerous if it was.
Not too sure what you’re getting at there… are you saying the meter operates as ‘David M’ says below… “painting on the needle and changing the value it points to” …
It is a normal analog meter: you connect it to a voltage (however derived – current shunt, etc) and the needle moves. Even if the display was completely blank, the needle would still move and you’d know there was some voltage in whatever you were measuring.
Ah, but that’s the problem. It ISN’T an “normal analog meter.” It’s driven by a DAC output from the micro, sez The Fine Article.
Untrue.
The needle needs about 40-50 µA up to 1-2 mA to move the full scale depending on the model, which means the meter itself will distort the outcome badly by loading up the circuit you’re measuring. This is why many analog meters have some kind of voltage follower or input buffer amplifier circuit run by batteries to reduce the load. No batteries – the needle doesn’t move.
Not all of them though. A typical analog dial multimeter that connects the dial straight to the circuit can have 20 kOhm per Volt input impedance, meaning that if you put it on the 10 Volt scale you will have 200 kOhms between the test leads. Try connecting that across a 100k resistor and scratch your head over why the voltage reads all wrong – well duh, you just changed the resistance to 67k. These meters are only meant for measuring strong voltage sources, like batteries.
Example:
https://electronicshelponline.blogspot.com/2013/08/hioki-3080-analogue-multimeter.html
Notice also how the meter has a “batt check” position in the power switch, between the off and on positions, so the needle would jump when you turn it on.
Despite how silly, this is. It would be kinda awesome to have an eink integrated into an analog multimeter. Bonus if a mirror could still be integrated into the dial face.
This.
I thought that’s what this was until I read the details.
It’s a grand idea, just missing that step.
How about just painting the needle on there and changing the value it points to. :)