In this instructable I will show you how to make DIY pocket size DC voltage meter with piezo buzzer for circuit check by yourself. All you need is basic knowledge in electronics and a little bit of time.

If you have any question or problems you can contact me on my mail: iwx.production@gmail.com

Some components were provided by DFRobot.

So let's begin

Step 1: Project Idea

The idea behind this project is very simple, to make a DC voltage meter that fits into a pocket with piezo buzzer for checking the circuits.

Step 2: Materials

Materials needed for this project can be bought on ebay, amazon or your local electronics shop.

For this project you will need:

-DC voltage meter

-9V battery

-piezo buzzer

-2-way toggle switch, you can also use 2-way slide switch

-9V battery connector

-PLA filament

-banana sockets (red and black)

Step 3: Housing

First I needed to measure all the components, so that I saw approximately how big housing I need to make.

Dimensions: 60x20x85mm

Then I have made a sketch in a program for 3D modeling, STL files of this two 3D models are attached.

Housing was 3D printed with white PLA filament. It is made out of two parts, the main case and the cover. Cover is then fastened with four screws onto the main case. On the front side there is one opening for inserting the voltage meter and two smaller holes for banana sockets.

On the left side is an opening for a toggle switch or a slide switch.

Step 4: Wiring

For supply i have used 9 V battery, mainly because of its ratio between size and capacity. Most of digital measurement tools use 9 V battery as supply.

Battery is connected to toggle switch, with which you can choose between measuring DC voltage or testing a circuit with piezo buzzer.

I have attached wiring diagram so you can see how to connect everything.

Step 5: Testing

After when all the wiring was done, I stared doing some tests. I have used Velleman digital multimeter for measurement results comparation. We need to know that this DIY voltage meter doesnt have calibrated measuring wires, so we can expect some errors in results.

For supply I have used Li-Ion battery (about 4.2V). Then i have measured voltage with DIY voltage meter and Velleman digital multimeter. Results were quite suprising, because I have expected higher error in measure results.

1.test:

Velleman digital multimeter -> result = 4.12 V

DIY digital voltmeter -> result = 4.17 V

As it can be seen from result, difference in 1.test was about 0.05 V.

2.test

Velleman digital multimeter -> result = 4.02 V
DIY digital voltmeter -> result = 4.06 V

Second result was a bit better, 0.04 V difference.

In the conclusion we can see that, the difference in the results is about 0.045 V. For better comparation, it would be needed to make more tests (min. 10) and then calculate arithmetic mean.