Design with MPR121 Capacitive Touch Sensor Breakout Board in Cirkit DesignerThe MPR121 Capacitive Touch Sensor Breakout Board is a sophisticated electronic component designed to add touch sensing capabilities to your projects. Utilizing the MPR121 chip, this breakout board can detect the touch or proximity of human fingers and provides a digital output signal for each of its 12 electrodes. Common applications include touch interfaces, interactive installations, and replacement of traditional buttons.
This circuit integrates an Adafruit MPR121 capacitive touch sensor with an Adafruit Feather 32u4 Bluefruit microcontroller. The MPR121 is powered by the Feather and communicates via I2C (SCL and SDA) to detect touch inputs, which can be processed or transmitted wirelessly by the Feather.
Open Project in Cirkit Designer
This circuit integrates an Adafruit MPR121 capacitive touch sensor with an Adafruit Feather 32u4 Bluefruit microcontroller. The MPR121 is powered by the 3.3V supply from the Feather and communicates with the microcontroller via I2C, with SCL connected to pin 3 and SDA connected to pin 2 of the Feather. This setup allows the Feather to detect touch inputs from the MPR121 for further processing or wireless communication.
Open Project in Cirkit Designer
This circuit features an Adafruit Feather nRF52840 Sense microcontroller connected to an ultrasonic sensor for distance measurement and an Adafruit AT42QT1010 capacitive touch sensor for touch input. The ultrasonic sensor's Trigger and Echo pins are interfaced with the microcontroller's digital pins D6 and D9, respectively, to send and receive ultrasonic signals. Additionally, a pressure-sensitive conductive sheet (Velostat) is connected in series with a 10k Ohm resistor to the microcontroller's analog pin A0, likely forming a pressure sensor.
Open Project in Cirkit Designer
This circuit is an interactive touch-based MIDI controller and audio player. It uses an Arduino UNO R4 WiFi to interface with an MPR121 capacitive touch sensor for input, a MAX7219 8-digit 7-segment display for visual feedback, and a DFPlayer MINI for audio output through a loudspeaker. The system detects touch inputs, plays corresponding sounds, and sends MIDI notes.
Open Project in Cirkit Designer| Pin Number | Pin Name | Description |
|---|---|---|
| 1 | IRQ | Interrupt output to microcontroller |
| 2 | ADDR | I2C address select pin |
| 3 | SDA | I2C data line |
| 4 | SCL | I2C clock line |
| 5 | VDD | Power supply (2.5V to 3.6V) |
| 6 | GND | Ground |
| 7-18 | ELE0-ELE11 | Electrode connections for touch inputs |
#include <Wire.h>
#include "Adafruit_MPR121.h"
// You can have up to 4 on one i2c bus (connecting ADDR to 3.3V, GND or leaving it floating)
// but you can only have one sensor per unique i2c address.
Adafruit_MPR121 cap = Adafruit_MPR121();
void setup() {
Serial.begin(9600);
while (!Serial) { // needed to keep leonardo/micro from starting too fast!
delay(10);
}
if (!cap.begin(0x5A)) {
Serial.println("MPR121 not found, check wiring?");
while (1);
}
Serial.println("MPR121 found!");
}
void loop() {
// Get the currently touched pads
currtouched = cap.touched();
for (uint8_t i=0; i<12; i++) {
// it if *is* touched and *wasnt* touched before, alert!
if ((currtouched & _BV(i)) && !(lasttouched & _BV(i)) ) {
Serial.print(i); Serial.println(" touched");
}
// if it *was* touched and now *isnt*, alert!
if (!(currtouched & _BV(i)) && (lasttouched & _BV(i)) ) {
Serial.print(i); Serial.println(" released");
}
}
// reset our state
lasttouched = currtouched;
// comment out this line for detailed data from the sensor!
delay(100);
}
Q: Can the MPR121 operate at 5V? A: No, the MPR121 is designed to operate between 2.5V and 3.6V. Using a higher voltage can damage the chip.
Q: How can I change the sensitivity of the touch detection? A: Sensitivity can be adjusted through the MPR121's internal registers. Refer to the datasheet for detailed register settings.
Q: Can I use the MPR121 with a microcontroller other than an Arduino? A: Yes, as long as the microcontroller supports I2C communication, you can interface with the MPR121.
Q: How do I clean the electrodes? A: Use a soft, dry cloth to gently wipe the electrodes. Avoid using any liquids or abrasive materials that could damage the board.
For further assistance, consult the MPR121 datasheet and ensure that your setup matches the recommended configurations.