The TTP223 Touch Button: a Lamp With Touch Control and Dimming

About the project

The TTP223 is a ready-made capacitive button: the chip calibrates itself, filters noise and outputs an ordinary digital signal. Unlike the ESP32 touch pins it works with any board, including an Arduino or an ESP32-C3, which have no touch inputs at all. It also works through 2–3 mm of plastic or wood — perfect for a switch hidden inside an enclosure.

What you need

• ESP32 DevKit (or an Arduino)
• A TTP223 module
• An LED and a 220 Ω resistor (or a MOSFET and an LED strip for a real lamp)

Wiring

The A and B jumpers

On the back of the module there are two pads you can bridge with a drop of solder:

A dimmable lamp needs the default mode: the sketch tells a short tap from a hold itself. In the simulator these jumpers are in the module properties.

Code

// Touch lamp: tap to switch on/off, hold to change the brightness
const int TOUCH_PIN = 4;    // TTP223 I/O (default mode, active HIGH)
const int LAMP_PIN = 25;

bool lampOn = false;
int brightness = 180;
int step = 5;
unsigned long touchedAt = 0;
bool wasTouched = false;
bool dimming = false;

void apply() {
  ledcWrite(LAMP_PIN, lampOn ? brightness : 0);
}

void setup() {
  Serial.begin(115200);
  pinMode(TOUCH_PIN, INPUT);
  ledcAttach(LAMP_PIN, 5000, 8);   // 5 kHz PWM, 8 bits
  apply();
}

void loop() {
  bool touched = digitalRead(TOUCH_PIN) == HIGH;
  unsigned long now = millis();
  if (touched && !wasTouched) {    // a finger just touched
    touchedAt = now;
    dimming = false;
  }
  if (touched && now - touchedAt > 600) {   // held: change the brightness smoothly
    dimming = true;
    lampOn = true;
    brightness += step;
    if (brightness >= 255 || brightness <= 10) step = -step;
    brightness = constrain(brightness, 10, 255);
    apply();
  }
  if (!touched && wasTouched && !dimming) {  // a short tap: toggle
    lampOn = !lampOn;
    apply();
    Serial.println(lampOn ? "Lamp ON" : "Lamp OFF");
  }
  wasTouched = touched;
  delay(20);
}

Press the module in the simulator with the mouse and let go — the lamp toggles. Hold for more than 0.6 s and the brightness starts "breathing" up and down; let go at the level you want.

Good to know

• Calibration at power-up. For about 0.5 s after power is applied the TTP223 memorises the "empty" level. If a finger is on the pad at that moment, the button works backwards or not at all until the next restart.
• Enclosure thickness. Through 2–3 mm of plastic the module works as is. For thicker material solder a 0–50 pF capacitor onto the Cs pads — more capacitance means lower sensitivity.
• Heavy loads. The TTP223 output gives a few milliamps; switch an LED strip through a logic-level MOSFET (IRLZ44N, AO3400), and a 230 V lamp through a relay or a solid-state relay.