DIY Digital RPM tachometer with Arduino

Some time we required to check the RPM of motor while creating projects. Few days back when i was creating a project that time i required a RPM techometer to check the rotational speed of motor but did not have the RPM meter then i decided to make it myself as i know how to make it and i had all the equipment required.
So in this article I am going to explain you about DIY Digital Tachomenter with Arduino.

This article is about DIY digital RPM tachometer, After reading this article you will be able to check the speed of dc motor or any kind of rotational device.

So just the take the advantage and update yourself.

Folloing things are required to make RPM meter.

  1. Optical speed sensor
  2. Arduino
  3. OLED display
  4. Breadboard
  5. Jumper wire

In the following video you can find the working demo of Arduino RPM tachometer.

Arduino Code

#define OLED_RESET 4
Adafruit_SSD1306 display(OLED_RESET);
#define NUMFLAKES 10
#define XPOS 0
#define YPOS 1
#define DELTAY 2
#define LOGO16_GLCD_HEIGHT 16
#define LOGO16_GLCD_WIDTH  16
static const unsigned char PROGMEM logo16_glcd_bmp[] =
    B00000000, B11000000,
    B00000001, B11000000,
    B00000001, B11000000,
    B00000011, B11100000,
    B11110011, B11100000,
    B11111110, B11111000,
    B01111110, B11111111,
    B00110011, B10011111,
    B00011111, B11111100,
    B00001101, B01110000,
    B00011011, B10100000,
    B00111111, B11100000,
    B00111111, B11110000,
    B01111100, B11110000,
    B01110000, B01110000,
    B00000000, B00110000
#if (SSD1306_LCDHEIGHT != 64)
#error("Height incorrect, please fix Adafruit_SSD1306.h!");
//------code for RPM----------------
int encoder_pin = 2;
// The pin the encoder is connected
unsigned int rpm;
// rpm reading
volatile byte pulses;
// number of pulses
unsigned long timeold;
// The number of pulses per revolution
// depends on your index disc!!
unsigned int pulsesperturn = 1;
void counter()
    //Update count
void setup()   {
    // by default, we'll generate the high voltage from the 3.3v line internally! (neat!)
    display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
    // initialize with the I2C addr 0x3D (for the 128x64)
    // init done
    // Show image buffer on the display hardware.
    // Since the buffer is intialized with an Adafruit splashscreen
    // internally, this will display the splashscreen.
    // Clear the buffer.
    // draw a single pixel
    //display.drawPixel(10, 10, WHITE);
    // Show the display buffer on the hardware.
    // NOTE: You _must_ call display after making any drawing commands
    // to make them visible on the display hardware!
    //-----------code for RPM---------------
    //Use statusPin to flash along with interrupts
    pinMode(encoder_pin, INPUT);
    //Interrupt 0 is digital pin 2, so that is where the IR detector is connected
    //Triggers on FALLING (change from HIGH to LOW)
    attachInterrupt(0, counter, FALLING);
    // Initialize
    pulses = 0;
    rpm = 0;
    timeold = 0;
void loop()
    if (millis() - timeold >= 1000){
        /*Uptade every one second, this will be equal to reading frecuency (Hz).*/
        //Don't process interrupts during calculations
        //Note that this would be 60*1000/(millis() - timeold)*pulses if the interrupt
        //happened once per revolution
        rpm = (60 * 1000 / pulsesperturn )/ (millis() - timeold)* pulses;
        timeold = millis();
        pulses = 0;
        //Write it out to serial port
        Serial.print("RPM = ");
        //Restart the interrupt processing
        attachInterrupt(0, counter, FALLING);
int valLen;
int displayWidth = 128;
int letterWidth = 18;
void updateDisplay(int rpm){
  if(rpm > 9999)
    valLen = 5;
  else if(rpm > 999)
    valLen = 4;
  else if(rpm > 99)
    valLen = 3;
  else if(rpm > 9)
    valLen = 2;
    valLen = 1;
  //-------------update display------------

        // text display tests
        display.setTextColor(BLACK, WHITE);
        // 'inverted' text
        // display.println(0xDEADBEEF, HEX);

Related Post

  1. Joey Schlatter 2 months ago

    i am a newbie and, i am trying to learn this display, so i copied the code and there are many errors coming up the the display has not been defined? I was able to get the example code for the display to work.

  2. JimInWoodstock 2 months ago

    Your code is missing the library names in the include statements. Is there an updated copy of the source that has the correct include statements?

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