How to Build a Switch Debounce Circuit for a Rotary Encoder

 

In this tutorial we look at how to combat switch bounce when using a rotary encoder with a debounce circuit made up of fairly basic components (see below). We use the KY-040 encoder as the test subject in the video. Below is the parts list from the video.

Parts list: BAS16-HE3-18 (Diode), SN74LVC1G17QDCKRQ1 (Schmitt Trigger), standard 0805 resistors (300ohms and 15kohms), and 4.7uF 0805 ceramic capacitor

Code from example ESP32 and KY-040 application in the video

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//This sketch demonstrates how to use the KY-040 encoder //link to KY-040 https://www.epitran.it/ebayDrive/datasheet/25.pdf //encoder pins #include <Adafruit_NeoPixel.h> #define ECLK 26 //encoder CLK pin #define EDT 25 //encoder DT pin #define ESW 35 //encoder SW pin #define LED_PIN 13 //pin for LED comm #define LED_CNT 1 //LED cnt #define BRIGHTNESS 125 //LED brightness setting //First argument is number of LEDs, second is arduino pin Adafruit_NeoPixel pixels = Adafruit_NeoPixel(LED_CNT,LED_PIN, NEO_GRB + NEO_KHZ800); const uint32_t off = pixels.Color(0, 0, 0); //RGB value for off const uint32_t white = pixels.Color(127, 127, 127); //RGB color for white const uint32_t blue = pixels.Color(30,144,255); //RGB color for blue const uint32_t red = pixels.Color(255, 0, 0); //RGB color for red volatile bool buttonFlag = false; //flag that tracks if button was pressed volatile uint8_t encoderFlag = 0; //flog for tracking encoder turns bool ledState = false; //tracks whether to turn LED off or on for button presses //interrupt service routine for an encoder turn CC or CCW void IRAM_ATTR ISR() { encoderFlag = true; } //interrupt service routine for an encoder button press void IRAM_ATTR ISR2() { buttonFlag = true; } void setup() { pinMode(ECLK,INPUT); //setup encoder pins pinMode(EDT,INPUT); pinMode(ESW,INPUT); attachInterrupt(ECLK, ISR, FALLING); //setup encoder interrupts attachInterrupt(ESW, ISR2, FALLING); pixels.begin(); //start RGB LED object pixels.setBrightness(BRIGHTNESS); //set LED brightness setLED(off); //set LED off } void loop() { if(encoderFlag) { //encoder knob was turned if(digitalRead(EDT)) { //encoder turned clockwise setLED(blue); } else { //encoder was turned counter clockwise setLED(red); } encoderFlag = false; //reset flag } if(buttonFlag) { //button was pressed buttonFlag = false; //reset flag if(ledState) { setLED(off); ledState = false; } else { setLED(white); ledState = true; } } } //sets LED to a specified RGB color //input is the RGB value void setLED(uint32_t color) { for(int i=0;i<1;i++){ pixels.setPixelColor(i,color); //set LED color pixels.show(); //send updated state to LED } }