====== Eeasterhegg 2024 Badge as Homeassistant Indicator Light ======

==== Goal ====

  * Control the brightness and activity of the beautiful EH2024 Badge via Homeassistant
    * which means, controlling it via esphome from an ESP module
    * which means, controlling it's supply voltage

==== HowTo ====


  * The badge takes 3V and about 200mA of power
  * It still works with about 1.8V where it takes about 50mA but has almost no activity and is very dark
  * which is perfect, so we can control it's activity by controlling it's supply voltage

Basically we want to trick the step-down module to generate less output by changing the feedback voltage it sees by generating an offset voltage using the ESP32's DAC. 

{{ :xro:eh2024_badge_esp32.svg |}}

  - To do that, we use a common StepDown module and connect it's Vin and GND to 5V and GND of an ESP32
  - We use the poti on the StepDown module to set it's output to slightly above 3V
  - We solder an extra pin to the module, onto the FB pin of the the modules step-down IC
  - via at least 10k of R we connect that FB pin to the ESP32's DAC
  - for fun, we also connect the Step-Down Modules Vout to an ADC pin of the ESP32
  - let's make sure the DAC output is 0V and re-measure the Step-Down Output and re-adjust it's poti so the output is exactly 3V (or a bit more if you want it brighter)
  - Flash the ESP32 with esphome
  - we are done

{{:xro:pxl_20241016_214556255.jpg?400|}}

=== Resources ===

  * [[https://github.com/btittelbach/esphome_config_examples/blob/main/eh_badge_power_indicator.yaml|ESPhome Example YAML]]
  * [[https://www.analog.com/en/resources/technical-articles/digital-adjustment-of-dcdc-converter-output-voltage-in-portable-applications.html|Helpful Document explaining different options of controlling power supply voltage]]

==== Result ====

{{:xro:20241017_002312-collage.jpg?400|}}

Badge controllable via HomeAssistant.