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Digital LED Voltmeter

This Digital LED Voltmeter measures the voltage at a particular point of the system it has been hooked up to and then provides a readout on its three 7-segment LEDs. This voltmeter is able to provide a readout of voltages from 2.5VDC to 30VDC within a 1% accuracy.

  • Range: 2.5VDC --- 30VDC
  • Display: Three 0.28" Red 7-Segment LEDs
  • Refresh Rate: ~1sec
  • Accuracy Within 1%

Digital LED Voltmeter Product Help and Resources

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May 2, 2018

This tutorial will show you how to make a robot that streams a webcam to a custom website that can be remotely controlled.

Dimensions for PRT-14313

A drawing with dimensions for this part can be found here.

Core Skill: Electrical Prototyping

If it requires power, you need to know how much, what all the pins do, and how to hook it up. You may need to reference datasheets, schematics, and know the ins and outs of electronics.

2 Electrical Prototyping

Skill Level: Rookie - You may be required to know a bit more about the component, such as orientation, or how to hook it up, in addition to power requirements. You will need to understand polarized components.
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Looking for answers to technical questions?

We welcome your comments and suggestions below. However, if you are looking for solutions to technical questions please see our Technical Assistance page.

  • Somebody get them a better quarter!

  • I want to measure a battery that is 12 volts and 18 amps. Will the high amps be a problem?

  • These are super handy, letting you add a voltage readout wherever you want. Got a homebrew multi-cell battery? Check the individual cell voltages in real time! Are these the "autoranging" kind that gain precision at <10V? I've seen two kinds of these - ones that have the decimal point fixed in an xx.x layout, and ones that ones that move between x.xx and xx.x as needed.

  • A datasheet please! This offering needs the tech specs!

    • Not much other than the stated voltage range and, around 3ma up to 20ma (depending on how segments are lit) within that voltage range.

  • So it pulls power from the same voltage source that it is measuring? I only see two wires coming out of it. Hoping to be able to make a measurement of a very high impedance voltage source (need to power the measurement electronics from a separate source).

    • You are correct, these are powered by the thing they're measuring. They draw about 7mA, depending on variant. Three-wire versions exist that are powered separately (and can measure down to 0.1V) - I believe Adafruit carries them.

  • From the features field above: Display: Three 0.28" Red 7-Segment LEDs I'd guess that they are RED.... Anyhow, at $1.50, that's not a bad price. BUT I'd bet the postage could be a deal breaker...

    Added comment: The postage for 20 of is the same as 1... about $5. So I ordered 20. At any rate these draw about 3ma up to 20ma (depending on how many segments are lit) within that voltage range. At any working voltage, (Most LED pilot lights will draw 3 to 10ma) they seem accurate enough for most needs, will auto down range below 10 volts (2 digits after the decimal), have a mystery controller chip and from some searching, may be hackable by removing the LED assembly and adding a 3rd wire to extend/isolate the voltage range. Similar to https://www.adafruit.com/product/705 at $8, This is a bargain!

  • What color are the LEDs?

Customer Reviews

5 out of 5

Based on 4 ratings:

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2 of 2 found this helpful:

A best-buy!

This is a great, little voltmeter at a great price. I installed the first one in my car to have a continuous read-out of battery voltage. I just added a small piece of red plastic used to improve the visibility of LED displays, Sparkfun might consider selling some of this filter material.

I'll just note that the specifications put the digit size at .28". My unit is actually about .38", which is just right for many applications.

4 of 4 found this helpful:

Love it! And the current is...

Without repeating the features or what's already been said, I checked one of these for current consumption (useful for some potential applications) - note that consumption fluctuates significantly, here I give a reasonable average over 10 sec. Part of the fluctuation depends on how many segments are lit! 2.5V: 0.21mA (dim but readable) 3.0V: 0.12mA 4.0V: 1.2mA 5.0V: 2.4mA 6.0V: 3.5mA (below 6V the display becomes less bright) 10.V: 5.4mA 15V: 4.9mA 20V: 2.1mA 25V: 1.6mA 29.5V: 2.2mA Note that I used the actual device to determine the voltage.

Love this thing!

For $1.50 how can you not buy this? I threw 5 of these in my cart and was so glad I did. These are great for so many things and work like magic.

Great little voltmeter...

... for such an incredible price to build into a project in a box, or to stick on an existing project or piece of hardware. A nice feature is the tiny potentiometer to adjust if the reading isn't spot on (for this price you weren't expecting 0.1%, right?) I bought three today and have already used one. I clipped off the longer leads on the back and hot melt glued a scrap piece of plastic on it for a back. Then it was glued to a DC power strip to monitor voltage on a battery backup system for my amateur radio station.

I second the notion of SparkFun stocking the red filter material; it seems to be hard to find, at least in small sizes and quantities.