Tachometer is a RPM counter which counts the no. of rotations per minute. There are two types of tachometer - one is mechanical and the other one is digital. Here we are going to design an Arduino based digital tachometer using IR sensor module to detect object for count rotation of any rotating body. As IR transmits IR rays which reflect back to IR receiver and then IR Module generates an output or pulse which is detected by the arduino controller when we press start button. It counts continuously for 5 seconds.
After 5 seconds arduino calculate RPM for a minute using given formula.
RPM= Count x 12 for single object rotating body.
But here we demonstrate this project using ceiling fan. So we have done some changes that is given below:
RPM=count x 12 / objects
object = number of blade in fan.
Required Components for Arduino Tachometer
- Arduino Pro Mini
- IR sensor Module
- 16x2 LCD
- Push button
- Bread board
- 9 volt battery
- Connecting wires
Circuit Diagram and Explanation
As shown in the above tachometer circuit, it contains Arduino Pro Mini, IR sensor module, buzzer and LCD. Arduino controls the whole process like reading pulse that IR sensor module generate according to object detection, calculating RPM and sending RPM value to LCD. IR sensor is used for sensing object. We can set sensitivity of this sensor module by inbuilt potentiometer situated on IR module. IR sensor module consist an IR transmitter and a photo diode which detects or receives infrared rays. IR transmitter transmits infrared rays, when these rays fall on any surface, they reflect back and sensed by photo diode (You can understand more about it in this Line Folloewr Robot). The output of photo diode is connected to a comparator, which compare photo diode output with reference voltage and result is given as output to arduino.
IR sensor module output pin is directly connected to pin 18 (A4). Vcc and GND are connected to Vcc and GND of arduino. A 16x2 LCD is connected with arduino in 4-bit mode. Control pin RS, RW and En are directly connected to arduino pin 2, GND and 3. And data pin D4-D7 is connected to pins 4, 5, 6 and 7 of arduino. A push button is also added in this project. When we need to count RPM we press this button to start this Arduino Tachometer to count RPM for five seconds. This push button is connected to pin 10 of arduino with respect to ground. You can learn more about the working of IR transmitter and receiver circuit in this circuit tutorial.
Arduino Tachometer Code Description
In code we have used digital read function to read output of IR sensor module and then calculate RPM.
// Code for Arduino Tachometer using IR Sensor
LiquidCrystal lcd(3, 2, 4, 5, 6, 7);
#define sensor 18
#define start 10
//unsigned int long k;
unsigned int count=0;
unsigned int time=0,RPM=0;
lcd.print(" Please Press ");
lcd.print("Button to Start ");