Showing Device State

With home automation, the need often arises to build remote switches or even complex dashboards to physically monitor and control devices.

Overview

This section explores strategies, concepts, and options for visually displaying the state of various devices. These concepts can be applied to any type of feedback you want to provide:

• Simple LEDs: Use a basic LED or lamp that turns on when a device is active and off when it is not. Advanced effects like blinking or pulsing can indicate additional states, such as “unavailable” or error conditions.
• WS2812 LEDs: Use addressable LEDs to represent states with color effects—e.g., green for an active device and red for an inactive one.
• Other Indicators: Utilize buzzers or alarms to signal specific conditions audibly. Once your dashboard is informed of a state change, you can trigger any action as needed.

Terminology

To ensure clarity, here are three key terms used throughout this discussion:

• Control: The switch or user interface that operates a device, such as a button on a remote control.
• Effector: The device being controlled, such as a fan or a garage door.
• Visual: The element that indicates the device’s current state—typically an LED, but it could also be a display, buzzer, or alarm horn.

Simple Cases

When a device integrates both effectors and visuals, implementation is straightforward. For example, in my remote-controllable 4-socket AC power strip:

• Effectors: Relays that switch the sockets on and off.
• Visuals: Bi-color LEDs that change between red and green based on power status.

In such cases, the ESPHome configuration is simple because effectors and visuals exist within the same ESPHome setup, allowing direct interaction between them.

switch:
  - platform: output
    name: "Switch1"
    icon: "mdi:power-socket-eu"
    restore_mode: RESTORE_DEFAULT_OFF
    output: relay1
    on_turn_on:
      then: 
        - output.turn_on: led1
    on_turn_off:
      then:
        - output.turn_off: led1

When the effector state changes—regardless of what caused the change—inside the ESPHome configuration, an event is raised: on_turn_on or on_turn_off, respectively.

This makes it trivial to tie the Visual to this event:

1. The state of the Effector changes (e.g., a plug is turned on). It does not matter who initiated this state change:
   • A physical button on the device may have toggled the plug.
   • Home Assistant may have triggered the change (e.g., via a smartphone app or an automation).
   • The change could be automatic, based on a sensor reading or another automated trigger.
2. A state change event is raised.
3. The event handler updates the Visual.

Since this scenario is straightforward, it is not covered in the remainder of this article. Visit this sample project to see the concept in action.

…And Challenging Scenarios

The real challenge begins when you want to create a dashboard or remote control with Visuals that exist in a separate device from the Effector(s):

• Remote Switch:
  You may want multiple remote controls placed in different locations, separate from where the Effector is. For example, you might want to control a lamp, garage door, or fan from multiple locations.

  When you turn on the Effector from any of these remote controls, you want all remote controls to update their Visuals accordingly—e.g., lighting a green LED to indicate the device is on.

  Note: Remote controls without Visuals (i.e., just buttons for control) are much easier to handle.

• Dashboard:
  You may want to create a more complex dashboard that monitors and controls multiple Effectors across your home.

  In this case, the Visuals exist in a separate device from the Effectors they monitor. However, you still want the dashboard to always reflect the real-time state of each device, even if the state changes due to actions outside the dashboard’s control.

Strategies

When a Visual is located in a different device than the Effector, there must be a notification process to ensure that the device with the Visual updates when the Effector changes state. There are two main approaches:

• Push:
  An automation script inside Home Assistant manages the Visuals in your monitoring device. In this approach, the monitoring device only displays Visuals, while Home Assistant centrally updates them.

  Since Home Assistant can manage all monitoring devices in one automation script, it provides a single point of control for maintaining relationships between Effectors and Visuals across multiple devices. This makes updates and maintenance simple:

  • If a device is renamed.
  • If you want to assign different Effectors to a remote control.

  Drawbacks:

  • Home Assistant updates Visuals only when an Effector state changes. If a monitoring device with Visuals was offline when the state change occurred, it will miss the update. To solve this, the automation script must detect when a monitoring device comes online and initialize its Visuals to match the current state of the Effectors.

• Pull:
  The device with the Visuals actively subscribes to Home Assistant events for the devices it wants to monitor. In this case, the monitoring device independently requests updates and manages its Visuals, with Home Assistant providing information on demand.

  Drawbacks:

  • The device requires full access to the Home Assistant API, making it a more valuable target for attackers. This is why Home Assistant no longer enables API access by default—you must explicitly allow it.
  • The monitored devices are hard-coded into the firmware of the monitoring device. If a device is renamed or you want to track different devices, you must update the firmware of every monitoring device.

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