This project contains PC power control via HomeAssistant and ESPHome ESP8266 NodeMCU. I use this project to power my ATX based NAS remotely on and off via Home Assistant.

Features:

Short press power button to turn PC on or graceful shutdown.
Long press power button to generate hard power-off.
Read power status motherboard (is PC turned on or off).
Use existing power / reset buttons at the front panel.

Hardware

The hardware consists of an ESP8266 and two IO pins, mounted on a PCI metal plate (see picture below). In my case I used an ESP8266 NodeMCU board. Theoretically any ESP8266 or ESP32 board can be used for this project.

One pin controls the power button by generating a long or short press and a second pin to read the power status of the ATX motherboard.

Schematic

My NAS is based on an Intel Core I7 ASRock Z97 ATX motherboard and contains standard 2x5 male connectors:

ATX header USB 2.0:

Header J1 pin 1 constant +5V power on pin 1, even when the PC is power-off and is used to power the NodeMCU. The ESP8266 or ESP32 is powered via an on-board 3V3 regulator.

ATX header System panel:

Header J2 contains the power, reset and GND pins:

Power button pin 6.
- Short press: Turn PC on or generate graceful shutdown.
- Long press: Generate hard power off.
Reset button pin 7.
- Used to read power status (not for hard reset)
GND pin 5.
Pin D1 is used to read the power status from the reset pin: High is on, Low is off. Transistor Q1 is used for secure isolation between ESP8266 and motherboard.
Pin D2 is used to pull the power button low to generate a short or long press. Resistor R1 is used to minimize current when the IO pin is accidentally set to output.

All ATX and ESP8266 pins must be operating at 3V3.

Downloads

KiCad schematic .SCH

Wiring

A DIY breakout PCB can be mounted at the system panel header to connect power button SW1 and reset button SW2.

There is sufficient space in the ATX computer case to mount the ESP8266 board and connecting a USB cable to program the ESP8266.

ESPHome

The ESPHome application consists of the two Yaml files. One configuration file and a second secrets.yaml to store passwords.

Documentation:

pc-power.yaml

esphome:
  name: pc-power
  platform: ESP8266 # ESP8266 or ESP32
  board: nodemcuv2  # Any ESP8266 or ESP32 board

wifi:
  ssid: !secret esphome_wifi_ssid
  password: !secret esphome_wifi_password

  # Enable fallback hotspot (captive portal) in case wifi connection fails
  ap:
    ssid: "PC Power Fallback Hotspot"
    password: !secret esphome_ap_password

# Enable logging
logger:

api:
  password: !secret esphome_api_password
ota:
  password: !secret esphome_ota_password

switch:
  - platform: gpio
    name: "PC Power button"
    icon: "mdi:electric-switch"
    pin: D2   # Power button output pin
    inverted: no
    id: power_pin
binary_sensor:
  - platform: gpio
    pin: D1   # Power detect input pin
    name: "PC Power Sense"
    device_class: power

secrets.yaml

esphome_api_password: "changeme"
esphome_ota_password: "changeme"
esphome_ap_password: "changeme"
esphome_wifi_ssid: "ssid"
esphome_wifi_password: "password"

Program ESP8266

Connect USB cable to ESP8266 board and enter the following commands. (Examples are tested on Ubuntu). For more information, refer to ESPHome.io.

# Install Python3 virtualenv
$ sudo apt install python3-virtualenv

# Create virtualenv
$ virtualenv venv

# Activate virtualenv
$ source venv/bin/activate

# Install ESPHome
$ pip install esphome

# Check ESPHome installation
$ esphome --help

# Upload program to ESP8266
$ esphome pc-power.yaml run

Select serial upload port

# Check logs
$ esphome pc-power.yaml logs

Home Assistant configuration

This section describes Home Assistant configuration.

Register ESP device

Configuration | Integrations: Add Integration: ESPHome
Select hostname or IP address of the ESP device.
Enter password as configured in secrets.yml esphome_api_password.

Create Automation Scripts

Two scripts are needed to generate a short and long pulse of the power button.

Configuration | Scripts | Add script:

Name: pc_power_button_short_press
Action type: Device
- Action: Turn on PC power button
Action type: Delay 600ms
Action type: Device
- Action: Turn off PC power button

Configuration | Scripts | Add script:

Name: pc_power_button_long_press
Action type: Device
- Action: Turn on PC power button
Action type: Delay 5s
Action type: Device
- Action: Turn off PC power button

Edit Dashboard | RAW Configuration Editor

  - title: PC
    path: pc
    badges: []
    cards:
      - type: button
        entity: switch.pc_power_button
        show_name: true
        tap_action:
          action: call-service
          service: script.pc_power_button_short_press
        name: PC Power Button
      - type: button
        tap_action:
          action: none
        entity: binary_sensor.pc_power_sense
        hold_action:
          action: none
      - type: button
        entity: switch.pc_power_button
        show_name: true
        tap_action:
          action: call-service
          service: script.pc_power_button_long_press
        name: PC Force OFF
        icon_height: 40px

Restart Home Assistant and ready to go!