ESPurna is an open source firmware for ESP8266 based wireless switch as such Sonoff POW, which I’ve been personally using to monitor my office’s power consumption. The developer, Xose Pérez (aka tinkerman), has now developed his own hardware with ESPurna-H board, as existing wireless switches with power monitoring functions would not fit into a gang box.
- WiFi Module – ESP12 with Espressif ESP8266 WiSoC
- Relay – Songle SRD-05VDC-SL-C 10A relay with NO and NC connection
- Power Monitoring – HLW8012 chip as found in Sonoff POW
- Expansion – 2x 5-pin header with the programming GPIOs, and two connections for external button and LEDs
- Misc – Reset button
- Power Supply
- Input – 100 ~ 240V AC
- Output – 5V up to 600 mA via Hi-Link HLK-PM01
- Safety – Optical isolation between the logic circuit and the relay circuit
- Dimensions – 50x50x20mm
Xose designed the board with Eagle 8.0 and released the schematics, PCB layout, BoM and other hardware design files under the Creative Commons Attribution-ShareAlike 3.0 Unported License (CC-BY-SA 3.0). You’ll find the files on github.
The board is not for sale, but you could purchase the PCB on OSH Park, purchase the components separately, and finally do the soldering yourself. Since this is a hobby project, not specific safety testing has been done, and you’d better understand what you are doing since the board is meant to be connected to the mains. Even companies do it wrong from time to time. If there’s a design flaw with the board it could overheat melting the plastic around, and in the worst case even start a fire.
Xose completed the setup with a capacitive touch switch attached to the cover, in order to turn on and off the light, and the final results above looks quite neat.