Tiny led voltmeter - help needed in finding the smallest one

Looked up the data sheet on the 3.0v voltage monitor linked by Helios and found this schematic

Looks pretty simple to use for just one led.

Thats whats so nice about them. Tiny, easy & uses very little current (0.5 uA typ). Also don’t need to be able to program chips. Just connect the voltage monitor chip, indicator led & resistor (aim for <50mA led current).
Haven’t ordered one yet since the attiny can do low voltage detection.

http://www.ebay.com/itm/micro-3-digits-0-28-LED-DC2-7-30-0V-variable-precision-GREEN-Digital-voltmeter-/251359299908?pt=LH_DefaultDomain_0&hash=item3a862e8944

I ordered one weeks ago, I think it is the smallest, with digits

Whoa that is small - size of a sim card. I looked around - cheapest is $5 shipped for these (vs $1.40 for the bigger guy), quite a jump in price for tinyness.

Interesting why the red is always cheaper than green/blue version - easier to build due to Vf probably?

I like the readout style over the lights. It's larger, but if I can fit it in, I will use the readout style. I don't really need a low voltage warning, I just think a readout of voltage would be kind of different.

Cheapest I could find:

RED:
http://www.ebay.com/itm/0-28-Digital-Panel-Meter-DC-2-5V-30V-Red-LED-Power-Monitor-Lithium-Car-Motor-/251303490316?pt=LH_DefaultDomain_0&hash=item3a82daf30c
Starts as low as 2.5V

YELLOW:
http://www.ebay.com/itm/0-28-Digital-Voltmeter-Power-Monitor-DC-2-6-30V-Voltage-Panel-Meter-Yellow-LED-/390625402570?pt=LH_DefaultDomain_0&hash=item5af3169eca
Starts at 2.6V

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

http://www.ebay.com/itm/gib-Two-Wire-0-28inch-LCD-Mini-Digital-DC-Voltmeter-Gauge-Voltage-Detector-/171173023012

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

http://www.plxdevices.com/product_info.php?id=MOBLLEGION055


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

definitely finding the lowest prices!

http://www.fasttech.com/products/0/10007685/1665901-vstar-s7-0-6-oled-variable-voltage-apv-mod

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

Adaruits

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.