Tachometer

Table of Contents

Background

This tachometer came about as a side project while designing my Cat Toy. I thought it would be interesting to know how fast the motor and all the gears were spinning so I watched videos on custom made tachometers. I followed the design on one of the videos and I designed a custom enclosure to be 3d printed.

Design

The device is designed to work by holding the end of it up to a spinning shaft. I usually 3d print an arm for the motor shaft to facilitate measurements. As the arm passes over the sensor, the device will count how long each pass takes and will convert that value into rotations per minute with the help of a microcontroller. The counting is done by the built in 16 bit timer on the Arduino. For this project I set the timer registers and created interrupt service routines so that the timing is exact. The 3d printed enclosure has a snap fit case so that it can be opened and closed without the need for screws.

Specifications

  • Power: 9v Battery
  • Mass: 72 g
>

Component List

Arduino Nano
IR Distance Sensor Breakout
SSD1306 128x32 OLED Display
9V Battery
Slide Switch

Block Diagram

Schematic

GitHub Code

Photos & Videos

Inside Tachometer
inside tachometer
Test #1

Moving my hand over the sensor about once per second gives a reading of about 60RPM

Test #2

Test with a dc brushed motor with an arm on the shaft for better reading

Ongoing Issues

  • Does not work for slow spinning motors at less than 60 RPM
  • Does not work in bright light
  • Difficult to line up and hold at correct position
  • Display sometimes shows innacurate readings briefly
  • LED should be visible when distance sensor switches on and off