ESP-Meter

This project is a little ESP32 which is used at home to monitor my

• Water Consumption
• Gas Consumption
• Power Consumption

The "meter" values are published to MQTT including Home Assistant Discovery messages. On top of that, I also emulate an Eastron SDM230 via Modbus to be able to limit energy export from my Growatt Inverter.

Disclaimer: this project does not claim to be a full product but is rather a place to document and share my findings in case anybody is interested.

Screenshots from Home Assistant

Schematics

Plugins

The individual "meters" are structured in a lame /plugins/structure.

Water Consumption

I have a regular water meter without any smartness or magnets attached. But it has a small wheel with reflective foil which is used to detect turns.

Used Hardware

• CNY70: Photodiode and Emitter-LED in a housing
• 100 Ohm resistor to limit current for the Emitter-LED
• 2.2k Ohm resistor to let voltage drop (and be measurable by ESP)

Approach

• Turn off LED
• Measure voltage (a) using ESP ADC
• Turn on LED
• Measure voltage (b) using ESP ADC
• (b) - (a) is the relevant value
• If value moves from low threshold to high threshold -> increase counter

Gas Consumption

I have a non smart gas meter. Luckily it as a small magnet in one of the ending digits.

Used Hardware

• Reed contact

Approach

• Debounce reed contact (50ms), on each falling edge -> increase counter

Power Consumption

My Smart-Meter eBZ DD3 already has an optical output interface which can be read out using a photo-diode.

Used Hardware

• Photodiode (not sure about the brand/make anymore)

Approach

• Read serial input
• Interpret OBIS messages

Eastron SDM230 Emulation

The Growatt inverter can use the Modbus to communicate to SDM power meters. This plugin emulates an SDM230so the inverter can limit its power output and not feed too much into the grid.

Used Hardware

• DSD TECH SH-U12 RS485 to TTL (MAX13487)

Approach

• Take current power from Power Consumption plugin
• Store into according registers

Known issues

While the general data looks fine on Growatt Cloud (and export limiting works), the inverter seems to overshoot quite some times and bounces around the limit.

Screenshots from Growatt Cloud