Tiny led voltmeter - help needed in finding the smallest one

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Old-Lumens
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Tiny led voltmeter - help needed in finding the smallest one

Hi,

I want to put a volt meter in a light using 2S Li-ion. I remember a long time back, someone on CPF had come up with a tiny one and they used it in a Maglite body. I would love to find the smallest one possible, even if it's just something that would only light if the voltage dropped. I have seen some with led readouts, but they are just too big at 30mm or so.

Anyone have any suggestions on anything very small? (less than 20mm)

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Edited by: Old-Lumens on 05/05/2014 - 22:35
AlexGT
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wight
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I’d say you want a 2s lipo alarm. Unfortunately most of the modern ones are built for connecting to the balance connector of a battery pack, you won’t have that (a tap between two two cells). It looks like this one is widely available though:
Doohan 2S Audible Voltage Lipo Alarm

Just remove any buzzers / LEDs you don’t want.

The first place I looked was at Hobbyking but it looks like they only carry the balance tap ones these days.

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WarHawk-AVG
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I use these, very good little voltmeters, won’t power up unless there is 3.2vdc however
I have one tied into one of those cheap portable power units to monitor the voltages going to the battery

https://www.fasttech.com/p/1222900 <-blue
https://www.fasttech.com/p/1222901 <-green
https://www.fasttech.com/p/1222902 <-red

wight
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31mm is too big…

Still fine, still on a break. One day I’ll catch up with you folks! previous wight catchup Wink
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Helios-
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ebay.com/itm/LED-Battery-level-voltage-monitor-meter-indicator-Alkaline-Nicad-NiMh-LiPo-L

For the smallest one possible you could have someone make you one using a dedicated voltage monitor chip. They can light up an indicator led when the voltage drop to the level the chip is preset for. 3.0v Voltage Monitor


Counterfeit 18650s, 2,<a href=“http://

wight
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Wow, that one’s really sweet Helios-. Where did you come across that?

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wight wrote:
Wow, that one’s really sweet Helios-. Where did you come across that?

Yeah they are…that’s pretty cool!
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This is the one jayrob over at CPF uses on his mag mod with voltmeter in this thread

http://www.candlepowerforums.com/vb/showthread.php?335007-FS-1000-Lumen-...!

This is the voltage monitor used

http://www.wr-store.com/product_info.php?cPath=21&products_id=104

HTH
AlexGT

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wight wrote:
Wow, that one’s really sweet Helios-. Where did you come across that?

I don’t recall. i came across it some time ago. Its sort of expensive for what it is IMO.


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Old-Lumens
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Thanks for the ideas. Helios- Love those links.     AlexGT- Yep, that's the thread, Thanks.

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larryk
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These are what I use on some of my spotlight builds. They are smaller at 23mm X 15mm X 10mm, but might fit in a Maglite. They are cheap and work great.

http://www.ebay.com/itm/gib-Mini-Digital-Voltmeter-DC0-100V-LED-Panel-Voltage-Meter-with-Three-Wires-/171124030115?pt=LH_DefaultDomain_0&var=&hash=item27d7c97aa3

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For just a single 3-5mm panel led could you use an op amp and a few resistors? Might fit on a small board ~ 15mm.

Edit-Like this maybe Matt could help you with the board

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islisis
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seems these days programmable drivers offer a lot of flexibility…it might be possible to program one of these drivers to get the functionality needed
http://budgetlightforum.com/node/30788
re. Star firmware: http://budgetlightforum.com/node/29150

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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.

Three Tanna leaves to give him life, nine to give him movement. But what if he eats the whole bag?

Scott

Helios-
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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.


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antoninodattola wrote:

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?

Old-Lumens
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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.

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Jerommel
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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-...LED-/390625402570?pt=LH_DefaultDomain_0&hash=item5af3169eca
Starts at 2.6V

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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.

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Dang! Making em smaller and smaller!

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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?

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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

Old-Lumens
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antoninodattola wrote:

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!

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antoninodattola
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Old-Lumens wrote:

antoninodattola wrote:

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!

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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.

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That’s James Bond kinda cool!

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

https://www.tindie.com/products/FriedCircuits/usb-tester-oled-backpack-w...

Adaruits
https://www.adafruit.com/products/661
128×32 SPI OLED graphic display

Even smaller
http://www.buydisplay.com/default/96×39-pixel-0-83-inch-small-oled-disp...
96×39 Pixel 0.83 inch Small OLED Display

Smaller still
http://www.buydisplay.com/default/oled-display/64×48-dot-matrix-0-66-ol...

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

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scottyhazzard wrote:
18.4 × 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

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