Arduino Interfacing Rotory_Encoder

Arduino Interfacing Rotory Encoder

How does a Rotary Encoder Work?

A Rotary Encoder is an electromechanical transducer, meaning it converts mechanical movements into electronic pulses. It consists of a knob which when rotates will move step by step and produce a sequence of pulse trains with pre-defined width for each step. There are many types of Encoders each with its own working mechanism, we will learn about the types later but for now let us concentrate only on the KY040 Incremental Encoder since we are using it for our tutorial.

The internal mechanical structure for the Encoder is shown below. It basically consists of a circular disc (grey colour) with conductive pads (copper colour) placed on top of this circular disc. These conductive pads are placed at an equal distance as shown below. The Output pins are fixed on top of this circular disc, in such a way that when the knob is rotates the conductive pads get in contact with the output pins. Here there are two output pin, Output A and Output B as shown in the figure below.

The output waveform produced by the Output pin A and Output B is show in blue and green colour respectively. When the conductive pad is directly under the pin it goes high resulting it on time and when the conductive pad moves away the pin goes low resulting in off time of the waveform shown above. Now, if we count the number of pulses we will be able to determine how many steps the Encoder has been moved.

Now the question may arise that, why do we need two pulse signals when one is enough to count the number of steps taken while rotating the knob. This is because we need to identify in which direction the knob has been rotated. If you take a look at the two pulses you can notice that they both are 90° out of phase. Hence when the knob is rotated clockwise the Output A will go high first and when the knob is rotated anti-clockwise the Output B will go high first.

The first two pins (Ground and Vcc) is used to power the Encoder, typically +5V supply is used. Apart from rotating the knob in clock wise and anti-clockwise direction, the encoder also has a switch (Active low) which can be pressed by pressing the knob inside. The signal from this switch is obtained through the pin 3 (Switch). Finally it has the two output pins which produce the waveforms as already discussed above. Now let us learn how to interface it with Arduino.

Circuit Diagram

Code :-

//Prateek //www.prateeks.in #include <LiquidCrystal.h> LiquidCrystal lcd(8, 9, 10, 11, 12, 13); #define outputA 6 #define outputB 7 int counter = 0; int aState; int aLastState; void setup() { pinMode (outputA,INPUT); pinMode (outputB,INPUT); Serial.begin (9600); lcd.begin(16,2); // Reads the initial state of the outputA aLastState = digitalRead(outputA); } void loop() { aState = digitalRead(outputA); // Reads the "current" state of the outputA // If the previous and the current state of the outputA are different, that means a Pulse has occured if (aState != aLastState){ // If the outputB state is different to the outputA state, that means the encoder is rotating clockwise if (digitalRead(outputB) != aState) { counter ++; lcd.clear(); } else { counter --; counter = constrain(counter,0,360); lcd.clear(); } Serial.print("Degree: "); Serial.println(counter); lcd.setCursor(0, 0); lcd.print("Degree: "); lcd.setCursor(10, 0); lcd.print(counter); } aLastState = aState; // Updates the previous state of the outputA with the current state }