ESP32 Smart PC Power Button

An ESP32-based device that simulates a PC power button, allowing remote control and automatic startup after power outages.

Features

• Remote PC power control
• Automatic wake-up based on network device monitoring
• Web interface for configuration and management
• REST API for automation and integrations

Table of Contents

• ESP32 Smart PC Power Button
• Features
  • Table of Contents
• How It Works
• Hardware Requirements
• Wiring Diagram
• Software Stack
• Quick Start
• Installation
  • 1. Flash MicroPython
  • 2. Download code
  • 3. Upload Firmware to ESP32
  • 4. Configure Settings
  • 5. Run the Device
• General Configuration
• REST API
• Home Assistant Integration Example
• Future Improvements
• License

How It Works

The ESP32 connects to your local network and monitors selected devices (any wifi device in network).

When Auto Power On is enabled:

1. The ESP32 periodically checks whether the monitored device responds to network requests.
2. If the device becomes reachable while the PC is still off, the ESP32 triggers the motherboard power button signal using an optocoupler.
3. The PC powers on automatically.

This allows the computer to recover automatically after power outages when restoring the last state and WoL don't work.

When Auto Power On is disabled, the device behaves like a simple Wi-Fi-controlled power button that can be triggered through the Web UI or REST API.

Note

Because the PC's status is checked via the network connection, the Auto Power On feature may cause an endless reboot loop if there are network issues on the PC's end.

Hardware Requirements

• ESP32‑C3 SuperMini (or compatible ESP32 board)
• PC817 optocoupler
• 330Ω resistor
• Jumper wires
• Optional breakout board
• Optional enclosure

Note

Some ESP32‑C3 SuperMini boards have weak Wi‑Fi signal stability because the antenna is placed very close to other components. A simple fix is to solder a ~3 cm copper wire to the antenna pad indicated in the diagram.

Some boards also lack an exposed reset pin, so you may need to solder directly to the reset button pads.

Wiring Diagram

The full wiring diagram and assembly example are shown below.

Software Stack

• MicroPython -- ESP32 firmware
• SolidJS -- Web interface
• Node.js -- frontend build system

Quick Start

1. Flash MicroPython to the ESP32-C3.
2. Download latest available version on Releases page.
3. Upload the contents of the esp32 directory to the device.
4. Edit esp32/settings.py and set your Wi-Fi credentials.
5. Restart the ESP32.
6. Open the ESP32 IP address in your browser to access the Web UI.

The device is now ready to control your PC power button.

Installation

1. Flash MicroPython

Download firmware for ESP32‑C3:

https://micropython.org/download/ESP32_GENERIC_C3/

You can flash it using esptool or:

https://adafruit.github.io/Adafruit_WebSerial_ESPTool/

2. Download code

The latest available version can be found on the Releases page.

3. Upload Firmware to ESP32

Upload the contents of the esp32 directory to the device.

A convenient method is using Thonny IDE:

https://thonny.org/

Setup guide:

https://randomnerdtutorials.com/getting-started-thonny-micropython-python-ide-esp32-esp8266/

4. Configure Settings

Add wifi.txt with WiFi credentials:

YOUR_WIFI
YOUR_PASSWORD

You can also edit settings.py to set GPIO pin.

# esp32/settings.py

# GPIO pin connected to optocoupler
s_pin = 4

5. Run the Device

After uploading the files, restart the ESP32.

The device will connect to Wi‑Fi and print the assigned IP address in the serial console or find the device by its hostname esp32-pc-button.

Open the address in your browser to access the Web UI.

General Configuration

Field	Description	Notes
auto_power_on	Automatically powers on the PC when the monitored device becomes available
host_ip	IP address used to check whether the PC is online	Must be a valid IPv4 address
target_ip	IP address of the device being monitored	Must be a valid IPv4 address
heartbeat_interval_s	Time interval between connectivity checks	Not recommended to set lower than 30 seconds
retry_delay_s	Delay before retrying power-on if the PC did not start	Should be higher than PC boot time (e.g., 1.5–2×)
status_sample_size	Number of consecutive checks to confirm online/offline status	Range: 1–10; higher values reduce false positives
allow_power_retry_limit	Enables limiting the number of power-on retry attempts
power_retry_limit	Maximum number of retry attempts	Required when retry limit is enabled; minimum: 1

REST API

Access the API through the IP address assigned to the ESP32.

Method	Endpoint	Description
GET	/api/config	Get current configuration
PUT	/api/config	Update configuration
GET	/api/signal	Trigger power signal
GET	/api/retry_clear	Clear retry counter
GET	/api/ping_status	Get device monitoring status
GET	/api/sys/reboot	Reboot ESP32
GET	/api/sys/info	Get system information
GET	/api/sys/logs	Get system logs

Home Assistant Integration Example

Example REST command configuration:

rest_command:
  pc_power_on:
    url: "http://ESP_IP/api/signal"
    method: GET

Example button:

button:
  - platform: template
    buttons:
      pc_power_button:
        friendly_name: "Power PC"
        press:
          service: rest_command.pc_power_on

Future Improvements

Planned ideas and possible future enhancements:

• Wi-Fi setup mode (initial configuration through a temporary access point)
• Wi-Fi reset functionality to clear saved credentials and re-enter setup mode
• Add the ability to configure multiple devices for control.
• Allow monitoring multiple network devices simultaneously
• Add MQTT support for deeper Home Assistant integration
• Improve network monitoring logic (custom intervals, retries, thresholds)

License

This project is licensed under the MIT License.

See the LICENSE file for details.