ESP32 - Limit Switch

This tutorial instructs you how to use the Limit Switch with ESP32.

ESP32 with Limit Switch

It is important to note that this tutorial is specifically about using a Limit Switch, please do not confuse with the following:

Hardware Used In This Tutorial

1×ESP-WROOM-32 Dev Module
1×USB Cable Type-C
1×Limit Switch (KW12-3)
1×Limit Switch (V-156-1C25)
1×Jumper Wires
1×(Optional) DC Power Jack
1×(Recommended) ESP32 Screw Terminal Adapter

Or you can buy the following sensor kits:

1×DIYables Sensor Kit (30 sensors/displays)
1×DIYables Sensor Kit (18 sensors/displays)
Disclosure: some of these links are affiliate links. We may earn a commission on your purchase at no extra cost to you. We appreciate it.

Introduction to Limit Switch

It is called Limit Switch because its main functionality is to detect the moving object reaching a limit.

A Limit Switch is so named because its primary purpose is to detect when a moving object has reached a limit.


There exist various types of limit switches, but among the most commonly used are the KW12-3 and V-156-1C25. Each of these types features three pins:

  • C pin: This is the common pin, it is used in both normally open and normally closed modes.
  • NO pin: This is the normally open pin, it is used in the normally open mode.
  • NC pin: This is the normally closed pin, it is used in the normally closed mode.
Limit Switch Pinout
image source:

How It Works

A typical Limit Switch application typically uses only two pins, the C pin and one of the remaining two pins. This results in four different ways to use a Limit Switch. The table below illustrates the wiring and reading state on an ESP32 for each of these four methods.

C pin NO pin NC pin ESP32 Input Pin's State
1 GND ESP32 Input Pin (with pull-up) not connected HIGH when untouched, LOW when touched
2 GND not connected ESP32 Input Pin (with pull-up) LOW when untouched, HIGH when touched
3 VCC ESP32 Input Pin (with pull-down) not connected LOW when untouched, HIGH when touched
4 VCC not connected ESP32 Input Pin (with pull-down) HIGH when untouched, LOW when touched

By swapping the GND pin and ESP32 Input Pin for each of the four ways, there are a total of eight different ways to connect an ESP32 to a Limit Switch.

Out of the eight ways, the tutorial will focus on one method, specifically the first method will be used as an example.

Wiring Diagram

ESP32 Limit Switch Wiring Diagram

This image is created using Fritzing. Click to enlarge image

If you're unfamiliar with how to supply power to the ESP32 and other components, you can find guidance in the following tutorial: How to Power ESP32.

To make the wiring connection stable and firm, we recommend using to solder wires and limit switch's pin together, and then use to make it safe.

For a stable and secure connection, it is recommended to use a soldering iron to solder the wires and Limit Switch pins together, and then use heat shrink tubes for added safety.

ESP32 Code - Limit Switch

Just like a button, a limit switch also needs to be debounced (See more at ). Debouncing make the code complicated. Fortunately, the ezButton library supports the debouncing functionm, The library also uses internal pull-up register. These make easy to us to program

Similar to a button, a Limit Switch also requires debouncing (more information can be found at Why needs debounce for the button/limit switch?). Debouncing can make the code more complex. However, the ezButton library offers debouncing functionality and utilizes internal pull-up registers, making programming easier.


Two common use cases for a Limit Switch are:

  • The first use case: If the switch is TOUCHED, perform a certain action. If the input state is UNTOUCHED, perform the opposite action.
  • The second use case: If the switch's state changes from UNTOUCHED to TOUCHED (or TOUCHED to UNTOUCHED), perform a specific action.
/* * This ESP32 code is created by * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit */ #include <ezButton.h> ezButton limitSwitch(17); // create ezButton object that attach to ESP32 pin GPIO17 void setup() { Serial.begin(9600); limitSwitch.setDebounceTime(50); // set debounce time to 50 milliseconds } void loop() { limitSwitch.loop(); // MUST call the loop() function first if(limitSwitch.isPressed()) Serial.println("The limit switch: UNTOUCHED -> TOUCHED"); if(limitSwitch.isReleased()) Serial.println("The limit switch: TOUCHED -> UNTOUCHED"); int state = limitSwitch.getState(); if(state == HIGH) Serial.println("The limit switch: UNTOUCHED"); else Serial.println("The limit switch: TOUCHED"); }

Quick Instructions

  • Follow the wiring diagram provided above to connect your Limit Switch to ESP32.
  • Connect your ESP32 to your PC using a USB cable.
  • Open the Arduino IDE software.
  • Install the ezButton library. Refer to the instructions
  • Select the appropriate board and port in the Arduino IDE.
  • Compile and upload the code to the ESP32 board by clicking the Upload button in the Arduino IDE.
  • Test the Limit Switch by touching and releasing it.
  • Observe the output on the Serial Monitor in the Arduino IDE.
The limit switch: UNTOUCHED The limit switch: UNTOUCHED The limit switch: UNTOUCHED The limit switch: UNTOUCHED -> TOUCHED The limit switch: TOUCHED The limit switch: TOUCHED The limit switch: TOUCHED The limit switch: TOUCHED The limit switch: TOUCHED The limit switch: TOUCHED The limit switch: TOUCHED The limit switch: TOUCHED The limit switch: TOUCHED The limit switch: TOUCHED The limit switch: TOUCHED -> UNTOUCHED The limit switch: UNTOUCHED The limit switch: UNTOUCHED The limit switch: UNTOUCHED The limit switch: UNTOUCHED
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Clear output
9600 baud  

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