DIY Digital RPM tachometer with Arduino

Sometimes we are required to check the RPM of the motor while creating projects. A few days back when I was creating a project that time I required an RPM Tachometer to check the rotational speed of the 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 RPM Tachometer 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.

Following things are required to make RPM tachometer.

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 the RPM Tachometer with Arduino

Arduino Code for RPM techometer

#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#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!");
#endif
//------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
pulses++;
}
//-----------------------------------
void setup() {
Serial.begin(9600);
// 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.
//display.display();
//delay(2000);
// Clear the buffer.
//display.clearDisplay();
// 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!
//display.display();
//delay(2000);
//-----------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
detachInterrupt(0);
//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 = ");
Serial.println(rpm,DEC);
updateDisplay(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;
else
valLen = 1;

//-------------update display------------

display.clearDisplay();
// text display tests
display.setTextSize(1);
display.setTextColor(WHITE);
display.setCursor(30,0);
display.println("CircuitMagic");
display.setTextColor(BLACK, WHITE);
// 'inverted' text
//display.println(3.141592);
display.setTextSize(2);
display.setTextColor(WHITE);
display.setCursor(45,20);
display.println("RPM");
display.setCursor((displayWidth/2)-(letterWidth/2*valLen),42);
display.setTextSize(3);
display.println(rpm);
// display.println(0xDEADBEEF, HEX);
display.display();
//----------------------
}

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