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Currently out of stock on all Bargraph Volt Meter (+ Tin) products. We will be sourcing more soon.

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The Bar Graph Voltage Meter

This is a very useful, easy to build, small voltage measuring meter. It allows quick testing of low voltage levels.

Although using just 4 LEDs (low resolution), it is ideal for testing out 0.5V to 6V levels. It is also adjustable via a trim pot control so you can set the resolution of the comparators. For example setting a 1 Volt resolution gives you values of 1V to 3V in one volt jumps. Setting it to 0.5 volts gives you a range of 0.5V to 1.5V. Setting it to 2 Volts gives you levels at 2, 4 and 6V.

This circuit uses a single IC that holds four basic comparitors. Keeping the soldering down to an absolute minimum. This can be soldered up ready for testing in about ten minutes.

Very useful if you need to monitor a specific voltage level. Acts as a low cost voltage meter. Using a 9 volt battery will give you reasonably stable voltage readings for most of the batteries life. Of course the input voltage could also come via a regulator if more accuracy was required.

All kits that you buy will all come with two detailed videos, one will describe the theory the second video will show how to drill and adapt the tin so your board fits within it. (both videos displayed on this page below)

Kit parts are as follows:
  • 1 of PCB board
  • 4 of 1Kohm Resistors (R1-R4)
  • 1 of 100Kohm Trim Pot (VR5)
  • 4 of 1Kohm Resistors (R6-R9)
  • 1 of LM339 Comparator Quad Pack (IC1)
  • 4 of 3mm LEDs
  • 1 of Battery clip
  • The tin (95mm x 60mm x 21mm)
  • Assembly instructions
(11 components)

The theory behind the circuit

The theory video is not required to get your circuit running. Those who are not interested in how the circuit works can just use the assembly instructions and refer to the second tin installation video for tips and an example on how to install the circuit within a typical enclosure. The theory is just an extra bonus video for those who like to know how their kits work.

NOTE: Video below is in HD quality so please view it in full size for best effect.

Tin Installation Video

NOTE: Video below is in HD quality so please view it in full size for best effect.


All kits that you buy will all come with a tin as an enclosure. (96mm x 60mm x 21mm) This short video goes through some suggestions on how to install your finished circuit into a typical enclosure. Often the tins used in the installation videos is a smaller tin for demonstration purposes. But you will always receive the larger tin version.