12x12x7.5mm Tactile Push Button Switch - 4 Pin Through-Hole PCB Mount Momentary Tact Switch for Arduino, ESP32 & DIY Electronics - TYPE: B

A four-pin tact switch does not have four separate contacts. The two pins on the same side are permanently joined inside the switch, whether it is pressed or not. This catches almost everyone once.

So wire across the switch, never along it. If your button appears permanently pressed, you have used the two pins on the same side - move one wire to the opposite side and it will work. On a breadboard, straddle the centre channel and the orientation takes care of itself.

You do not need an external resistor. Every Arduino, ESP32, ESP8266, STM32 and Raspberry Pi has an internal pull-up you can switch on in software: one side of the button to the GPIO pin, the other side to GND. The pin then reads HIGH at rest and LOW while pressed.

const int BUTTON = 2; void setup() {  pinMode(BUTTON, INPUT_PULLUP);   // internal pull-up on, no resistor needed  Serial.begin(9600); } void loop() {  if (digitalRead(BUTTON) == LOW) { // LOW means pressed    Serial.println("pressed");    delay(200);                     // crude debounce  } }

If you prefer an external pull-up, a 10kΩ resistor from the pin to 3.3V or 5V does the same job and makes the circuit readable on a schematic.

A mechanical switch does not close cleanly. The contacts chatter for a few milliseconds, and a microcontroller polling fast enough will see one press as three or four. The fix is either software - ignore further changes for 20 to 50ms after the first - or hardware, a 100nF capacitor across the switch contacts. Every beginner meets this, and it is worth meeting it deliberately rather than chasing a fault that is not there.

• Reset, mode and menu buttons on a custom controller or front panel
• User input on Arduino, ESP32 and ESP8266 projects
• Manual override on a relay board or automation controller
• Start, stop and select on robots and test rigs
• Replacing a failed button on an existing board - 12 x 12 is a common original fitment
• Teaching digital input, pull-ups and debouncing, where a button you can actually feel matters

Arduino UNO, Nano and Mega, ESP32, ESP8266, STM32, Raspberry Pi and Pi Pico, plus breadboards, perfboard and through-hole PCBs. Nothing about it is board-specific.

12x12x7.5mm 4-pin tactile push button switch