Tiny led voltmeter - help needed in finding the smallest one

Found some better prices now, $1.90 for red to $2.46 for blue:


I don’t think they get cheaper than these. I’m probably going to grab some afterwards. I already have the bigger version in many colours, and I must say the blue LED is the most beautiful - kind of classy, expensive looking.

Dang! Making em smaller and smaller!

The numerical LED blocks are standard size. Three digits is too wide (>20mm). Maybe replace it with two digit block if one decimal place resolution is acceptable?

The ones from gigibaobao are better quality than FastTech, with trim pot and work to lower voltage, but still too big.

Another idea, maybe use two or three of the kind Helios posted set to different voltages?

It would take an OLED monitor this type of PLX


What do you say to use the monitor like that?? I think you can try!

definitely finding the lowest prices!


I never thought of OLED! Gotta research that!

look forward to hearing from you!

I ordered a few of them from Fasttech and they won’t read voltage until it rises above about 3.3 volts. They do work great for RC lipo monitoring & portable solar cell and checking batteries in the field with out lugging a huge Fluke meter.

That’s James Bond kinda cool!

Here is a “tindie” build with an OLED display…perhaps something can be modded up


128x32 SPI OLED graphic display

Even smaller
96x39 Pixel 0.83 inch Small OLED Display

Smaller still

18.4 x 18.1mm, that last one is really cool but how the heck do you program it for a voltage readout?

That is why the adafruit has the control board breakout

needs a tiny circuit to run it…and firmware

I think you could bitbang i2c with an ATtiny. You could take the voltage reading using the standard divider method on the ATtiny and then output it to the display. You’d need additional space for the larger firmware - probably an ATtiny85 with Arduino would be the most straightforward way to build it.

Ok, first two sentences were automatically translated into [I think you could BADA-BING SOMETHING with a THINGY. You could take the voltage reading using the standard DOO-DAD method on the THING-A-MA-JIGGER and then output it to the display]. I understood the last sentence just fine. More doo-dads and thingys suggests that it won’t fit in a small light. :wink:

Not at all! The Arduino environment works fine (ish) to write code for a bare ATtiny85, such as the ones we would use to replace an ATtiny13 in our flashlight drivers (they have a similar footprint). You simply write and compile your code to a hex file and then flash as we normally do. There wouldn’t be room for a lot of shenanigans (no stars), but I think there’s enough room for a momentary switch, voltage monitoring, and i2c. So the limiting factor is probably still the physical size of the display, although I did not look at what it needs for a power supply.

That sounds cool. Maybe a BEC like for radio control vehicles. They must be smaller by now. My last one was 22 years ago.

scottyhazzard I took a glance at the manual for that display. The tricky bit is that it wants two fairly different supply voltages. The good news is that it has an internal (boost) PSU for the higher voltage. The bad news is that the overlap between supply voltages is still very minimal, even taking advantage of that boost PSU. I think it’s possible that a simple 3.3v regulator such as the MIC5235 Microa mentions here could power the whole thing. It is a small component and requires one capacitor. The display itself requires 6 capacitors and 1 resistor when powered in this way. All in all I think it’s possible to add this stuff to a very small PCB or even onto an existing driver if there is a little bit of space. Any application that can accommodate a display of this size certainly has enough space. Even if running both VDDB and VDD off of 3.3v doesn’t cut it we could easily drive VDDB on one 3.5-4.0v MIC5235 and VDD on a nice comfortable 2.8v MIC4235. That’s still only 2 small components and 2 small capacitors. Bottom line is that there is no need for a bulky BEC (and the other bottom line is that needing 2 input voltages makes the BEC a less desirable route anyway).

EDIT: the display has a ribbon cable that requires soldering directly to a PCB. Rather than waste space why not just make that the PSU board and driver PCB as well?

Now for the host, what to put it in? Something that takes multiple cells I would think. M6, SRK or there’s that style that has 3 18650’s in parallel but one emitter…

Heh, no need to worry too much about that. If you build it they will come. :wink:

Unfortunately I doubt that anyone is jumping up and down to do the legwork required to actually get this working. I’m not. :frowning:

Sometimes it crosses my mind that a very small oled display could be neat. But then I remember its a flashlight. Bit excessive, no? Feels like you’d need to search for enough information to display in order to justify it. A tiny 7segment could be enough.

Kickstarter Oled flashlight

IIRC that’s what Rufusbduck has been advocating. (A 7-segment bar, ring, or similar - not a 7-segment numeric in case there was any confusion) We could easily drive one of those with a shift register attached to an ATtiny. They make shift registers who’s parallel outputs are already LED drivers.

At a glance maybe AS1109-BQFR or STP08DP05XTTR ?