New ESP32 energy monitoring component

Hello, I made an esphome component for ESP32 to measure electric power through ADC.
It is inspired to the good old Emonlib, which is found in almost all DIY energy monitors.
I kept the power estimation algorithm, but I cut some rough edges, making it sleeker and easier to configure.

Technical details

This component leverages DMA on the ADC peripheral in ESP32 chips. This allows for a much higher sample rate (20kHz), which in turn leads to almost perfectly synchronized samples, thus releasing the need for a phase calibration parameter (_PHASECAL in Emonlib) and making the result in theory more precise (I have not tested its precision, since I do not own precise measurement equipment).
On the other side it requires esp-idf v5.x or newer, which is at the moment not officially supported by the ESPHome project. It apparently works, but still could break something.

It is now in a beta state. There are some open points. Any feedback, help, feature request, performance benchmark or code contribution is highly appreciated.
Here is a sample configuration if you want to give it a try:


  board: esp32dev
    type: esp-idf
    version: 5.2.1

  - source: github://Petapton/esphome@emon
    components: [ emon ]

  - platform: emon
      pin: GPIO34
      attenuation: 2.5dB
      cal: 2.121e-1
      pin: GPIO35
      attenuation: 2.5dB
      cal: 2.8798e-2
    data_interval: 1s
      name: "Emon P1 Voltage"
      name: "Emon P1 Current"
      name: "Emon P1 Active Power"
      name: "Emon P1 Apparent Power"
      name: "Emon P1 Power Factor"

  # Reboot in safe mode before OTA updates
  - platform: safe_mode
    name: "Safe Mode"


Known issues

  • OTA update does not work unless booted in safe mode. This is most likely due to the fact that the ADC peripheral generates frequent interrupts, making the OTA process time out.

Hardware wise, is this only for Emon?

I’m sorry, I think I don’t understand your question.
You can hook it up to virtually any AC voltage-current signal pair and it will spit out power readings. Of course you will need extra circuitry to avoid frying your esp.
If you are interested in building custom hardware, please see the electricity monitoring guide by Openenergymonitor.

I mean, what kind of input your component is expecting? Let’s say if I have some voltage sensor and current transformer… I’m not interested in Emon hardware.

Yep, exactly that. A voltage transformer and a CT clamp.
As long as your signal stays in the ADC boundaries, you are good to go.

Sorry my stupid question, I didn’t notice that arrow to open “Technical details”.

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I happen to be in possession of a 4 channel PCB, so is it possible to use one channel for the voltage and the other 3 to report 3 different devices?

I think this is not supported at the moment, but should definitely be available in some later iteration. Nevertheless you could try setting up more than one entry in the yaml file and see if it works.
I expect it not to work. In such case, would you mind sending logs?
Thank you.

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This is very much an “on the bench” project at the moment, it’s kind of ready to go but there’s too many other plates that need attention. I’ll report back…

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