This repository encapsulates one phase energy monitor for ThingSpeak based on ESP8266-01 module, current transformer and precision rectifier.
Because ESP8266-01 has only two digital I/O pins (and also for resolution) is for A/D conversion used 18bit I2C A/D converter MCP3421 and fullwave precision rectifier realized via double operational amplifier LM258. For measuring current is used current transformer 30A SCT-013-030 which has already integrated shunt resistor.
For powering is used miniature 3.3V/600mA power supply from eBay such as http://www.ebay.com/itm/400761809788, but due to initial power requirements of ESP8266 i recomend 3.3V/1A power supply (which is also available through this seller).
Repository contains CadSoft's Eagle schematic and PCB layout. Because i do not have equipment for proper handling of SMDs (and also for use MCP3421 on breadboard) i created small DPS that holds MCP3421 and has standard DIP dimensions. Note: Some 100n capacitors is soldered directly to pins on bottom side of PCB.
Software can be uploaded to ESP8266 via Arduino IDE. For building you need MCP342x module which is available here https://github.com/uChip/MCP342X on GitHub. For first 5 minutes after module startup is available WiFi AP "EnergyMonitor" with HTTP server at 192.168.4.1:80 behind it. On this URL is available simple configuration page for setting WiFi parameters, ThingSpeak channel/field with write-key, mains voltage and other tunning parameters. After 5 minutes, when the page is not accessed, module starts automatically. After module connects to configured WiFi is configuration server available on internal network at DHCP assigned IP address. Default parameters can be set in source file.
There are also OpenSCAD and STL model for enclosure.
I use module for several months at home and also on cottage. My public channels on ThingSpeak are:
https://thingspeak.com/channels/150525
https://thingspeak.com/channels/157732
Here are some project images:
