Introduction: Tachometer

About: Hello Instrutables community! It is always a pleasure be on Instrutables, be it reading an instrutable or writing an instrutable. I am a mechanical engineer who is currently working for a large engineering com…

Hello everyone.

This time I will share my way of making a digital tachometer. It works great and can easily compete with a commercial version. On top of all, I wanted to avoid the complexity of adding a battery to the system. So I decided to make the tachometer power bank compatible.


Arduino Pro Mini

1306 OLED display

3144 Hall effect sensor

Small magnets

micro USB hub

wires, solder etc.

Step 1: Watch the Video

I made and added a video on youtube on my channel. Please watch it once before proceeding. I hope you will like the video.

Step 2: Make the Body

I am fortunate enough to have a 3D printer at my home. I understand that not all enjoy this luxury. The project is simple enough that it can be done without 3D printer. If someone of you makes it without 3D prints, please add the images to the project in comments section. It would be nice to see alternate approaches to the same destination.

Make sure the joint that you will use does not add a lot of friction. The way I made my rotor bearing was that I inserted the sharp end of a small nail into the cross of a cross head screw. This makes a metal metal point contact thus reducing the friction to almost none.

I have added the STL files in this step. Feel free to download and use them.

Step 3: Upload the Code

Please upload the code before doing the wiring. This is especially true if you are using arduino pro mini like I did.

It becomes impossible to programme the pro mini once the wires have been soldered to them. The main issue is that Pro mini has only one Vcc pin and that pin should be unused for the FTDI board's pins to pass through.

I have verified my code and it works just fine.

You can download the code form the given link.

Link for code

Step 4: Connect the Wires

Please make sure that you have programmed the microcontroller before soldering its Vcc pin

Wiring Schematic-

OLED display=

Vcc = Vcc

Gnd = Gnd

SCL = A5

SDA = A4

3144 Hall effect sensor

Gnd = Gnd

5V = Vcc


The two buttons for the Mode and the reading connect to D3 and D4.

Try to keep the wiring as short as possible. This is because at the end of the day you have to push all wires inside. Adding too much wire will induce unnecessary pressure inside the body and may not lead to happy time with your project.

Step 5: Stick the Hall Effect Sensor on the Body.

Make sure that you attach wires long enough for the hall effect sensor to fit very close to the motor. Also make sure that the sensor is not very oddly placed. Make sure that the rotor is comfortable inside the casing and around the hall effect sensor.

I have added images in which the sensor and the rotor's magnet us visible.

And its done. Hope your project also works as you expected it to.

If you have any questions or doubts, feel free to comment for message me.

Thanks for your time.