SENSORS/ACTUATORS

ESP32 MicroPython Limit Switch

This guide shows you how to use a limit switch with the ESP32 and MicroPython. We will cover the following details:

How to connect the limit switch with the ESP32.
How to write MicroPython code for the ESP32 to read the limit switch's status.
How to write MicroPython code for the ESP32 to detect the touched and untouched event from the limit switch.

Hardware Preparation

1	×	ESP-WROOM-32 Dev Module
1	×	USB Cable Type-C
1	×	Limit Switch (KW12-3)
1	×	Limit Switch (V-156-1C25)
1	×	Wires
1	×	(Optional) Heat Shrink Tubing
1	×	(Optional) Soldering Iron
1	×	(Recommended) Screw Terminal Expansion Board for ESP32
1	×	(Recommended) Power Splitter For ESP32

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 the links provided in this section are Amazon affiliate links. We may receive a commission for any purchases made through these links at no additional cost to you.
Additionally, some of these links are for products from our own brand, DIYables.

Overview of Limit Switch

It is called Limit Switch because its main function is to detect when a moving object reaches its endpoint. It is also known as a travel switch. It is also called the travel switch.

Pinout

Different types of limit switches are commonly used, such as the KW12-3 and V-156-1C25. Each model includes 3 pins.

C pin: This is the common pin. It is used in both the open and closed settings.
NO pin: This means the Open pin. It is used when the setting is open.
NC pin: This means the Closed pin. It is used when the setting is closed.

image source: diyables.io

How It Works

The limit switch has three pins, but usually, only two pins are used: the C pin and one of the other two pins. There are four ways to connect the limit switch. Here is a table showing the wiring of the limit switch and its readings on the ESP32 for all 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

We can change the positions of the GND pin and the input pin on the ESP32 for each method. This provides us with 8 different methods to connect the ESP32 to a limit switch.

We only need to choose one of the four methods mentioned earlier. For this tutorial, we will use the first method.

Wiring Diagram

How to connect ESP32 and limit switch using breadboard

This image is created using Fritzing. Click to enlarge image

How to connect ESP32 and limit switch using screw terminal block breakout board

ESP32 MicroPython Code - Limit Switch

A limit switch, similar to a button, requires debouncing to function properly. Debouncing can make the code more complex. Fortunately, the DIYables_MicroPython_Button library provides a debouncing feature and includes an internal pull-up resistor, which simplifies the programming process.

Here are two usual situations:

The first: If the switch is TOUCHED, do something. If it is UNTOUCHED, do the opposite.
The second: If the switch goes from UNTOUCHED to TOUCHED or from TOUCHED to UNTOUCHED, do something.

Let's see how to write the MicroPython script in both cases.

ESP32 MicroPython Code - Read Limit Switch's State

""" This ESP32 MicroPython code was developed by newbiely.com This ESP32 MicroPython code is made available for public use without any restriction For comprehensive instructions and wiring diagrams, please visit: https://newbiely.com/tutorials/esp32-micropython/esp32-micropython-limit-switch """ from DIYables_MicroPython_Button import Button import time # Initialize the limit switch connected to GPIO19 pin of the ESP32 limit_switch = Button(19) # Set debounce time to 50 milliseconds limit_switch.set_debounce_time(50) while True: limit_switch.loop() # Update the button state state = limit_switch.get_state() if state == 1: # GPIO HIGH print("The limit switch: UNTOUCHED") else: print("The limit switch: TOUCHED")

Detailed Instructions

Here’s instructions on how to set up and run your MicroPython code on the ESP32 using Thonny IDE:

Make sure Thonny IDE is installed on your computer.
Confirm that MicroPython firmware is loaded on your ESP32 board.
If this is your first time using an ESP32 with MicroPython, check out the ESP32 MicroPython Getting Started guide for step-by-step instructions.
Connect the ESP32 board to the limit switch according to the provided diagram.
Connect the ESP32 board to your computer with a USB cable.
Open Thonny IDE on your computer.
In Thonny IDE, go to Tools Options.
Under the Interpreter tab, choose MicroPython (ESP32) from the dropdown menu.
Make sure the correct port is selected. Thonny IDE usually detects it automatically, but you might need to select it manually (like COM12 on Windows or /dev/ttyACM0 on Linux).
On Thonny IDE, navigate to the Tools Manage packages on the Thonny IDE.
Search “DIYables-MicroPython-Button”, then find the Button library created by DIYables.
Click on DIYables-MicroPython-Button, then click Install button to install Button library.

Copy the provided MicroPython code and paste it into Thonny's editor.
Save the code to your ESP32 by:

Clicking the Save button or pressing Ctrl+S.
In the save dialog, choose MicroPython device.
Name the file main.py.

Click the green Run button (or press F5) to execute the script.
Press, hold, then release the limit switch while checking out the message in the Shell at the bottom of Thonny.

Shell x

>>> %Run -c $EDITOR_CONTENT

MPY: soft reboot The limit switch: UNTOUCHED The limit switch: UNTOUCHED The limit switch: UNTOUCHED The limit switch: UNTOUCHED The limit switch: UNTOUCHED 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: UNTOUCHED The limit switch: UNTOUCHED The limit switch: UNTOUCHED

MicroPython (ESP32) • CP2102 USB To UART Bridge Controller @ COM12 ≡

ESP32 MicroPython Code - Check Limit Switch's touched/untouched event

""" This ESP32 MicroPython code was developed by newbiely.com This ESP32 MicroPython code is made available for public use without any restriction For comprehensive instructions and wiring diagrams, please visit: https://newbiely.com/tutorials/esp32-micropython/esp32-micropython-limit-switch """ from DIYables_MicroPython_Button import Button import time # Initialize the limit switch connected to GPIO19 pin of the ESP32 limit_switch = Button(19) # Set debounce time to 50 milliseconds limit_switch.set_debounce_time(50) while True: limit_switch.loop() # Update the button state if limit_switch.is_pressed(): print("The limit switch: UNTOUCHED -> TOUCHED") if limit_switch.is_released(): print("The limit switch: TOUCHED -> UNTOUCHED")

Copy the above code and paste it to the Thonny IDE's editor.
Save the script to your ESP32
Click the green Run button (or press F5) to run the script. The script will execute.
Press, hold, then release the limit switch while checking out the message in the Shell at the bottom of Thonny.

Shell x

>>> %Run -c $EDITOR_CONTENT

MPY: soft reboot The limit switch: UNTOUCHED -> TOUCHED The limit switch: TOUCHED -> UNTOUCHED

MicroPython (ESP32) • CP2102 USB To UART Bridge Controller @ COM12 ≡

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