Friday, 18 August 2017

ESPLive v2.0 : The "ultimate" mains connected ESP8266

I decided that although there are many ESP8266 boards out there these days - and even some which are "mains connected" such as the fantastic Sonoff boards - none really fit my requirements for flexibility. As a result, the ESPLive was born.

The ESPLive v2.0 prototype with USB-Serial connected.


The ESPLive is simply an ESP8266 based ESP12F module with all of the pins broken out and a few nifty features. Of course, the most obvious feature is the mains power supply... I opted for a MeanWell IRM-02-5S to supply 5V at 2W (for relays and other power hungry devices).
  1. I like the NodeMCU way of flashing and so I added a couple of transistors so that I never have to push any buttons while developing firmware. 
  2. Since there is only one ADC on the ESP8266, I also added an analog multiplexor IC which lets me switch between two inputs.
  3. Through selectively soldering only certain resistors and jumpers it is possible to have 2 separate inputs, one of which has an optional voltage divider for 3.3 V or 5 V range (or more). The second input is direct or has a burden resistor that is biased to 0.5 V for current measurement with a current transformer.
  4. There are two transistor driven outputs capable of 300 mA for driving relays. These outputs also have robust flyback diode protection with a zener and rectifier diode. See this app note for why the zener is a good idea.


Firmware

I have used both espurna and Tasmota on these boards and I currently have one installed and running well with Tasmota in my Man Cave. The board is really small (about 3.5 x 5 cm) and so I wrapped it up in insulation tape and squeezed it into a light switch which had neutral available. A little bit dodgy but it works! ;)

I am working on some mods to the above firmwares (I haven't decided which is best yet) to control my how water geyser for maximum energy efficiency and also something to control my jacuzzi, gate, etc. 

I'm using Home-Assistant and Node-Red, which seem great so far! I'll post some articles on the setup at some point.

https://github.com/ManCaveMade/ESP-Live

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