Six months ago I was reviewing the AiThinker AiLight, a great looking light bulb with an embedded ESP8266EX microcontroller, driven by a MY9291 LED driver. Just before summer IteadStudio released it’s Sonoff B1 [Itead.cc] light bulb, heavily inspired (probably same manufacturer) by the AiLight, at least on the design.
Now that IteadStudio has become popular between the home automation community you can also find the Sonoff B1 on global marketplaces like Ebay or Aliexpress for around 13€.
A closer look at the B1 uncovers some important differences. But before going deeper into the details let me first say that this post will probably look more like a review, at least more than I use to write. And second, yes: ESPurna supports the Sonoff B1 🙂
Itead Studio has been releasing interesting gadgets for the Home Automation community based on a low price tag and extreme hackability. You can google “sonoff” (the main brand for Itead Studio home automation devices) to get more than a million hits, including official pages, reviews and lots of hacks. The ubiquitous ESP8266 (or its sibling ESP8285) is the core of all those devices, using WiFi instead of the traditional RF messages, replacing a remote with mobile apps or voice commands. But also, using custom firmware like ESPurna, technologies and solutions like MQTT, Node-RED or Home Assistant. But one of the latests devices from the chinese firm tries to bridge the gap between those two technologies: the Sonoff RF Bridge 433.
After a busy month I decided to spend some energy on doing hardware instead of software and the result was the ESPurna board I posted about just yesterday. The goal was to have a device based on the ESP8266 I could fit into my house wall gangs, with an SPDT relay to work with multi-way switches and power monitoring using the same IC the Sonoff POW uses: the HLW8012.
As a side project today I’ve been searching on the box of the TODO projects and I have rescued a KEMO STG15 [Ebay] plug housing with socket. These sockets are somewhat expensive and really bulky but the good thing is that there is quite some room to fit some electronics inside, but not a Sonoff board, too big.
If you have read me, you might know I have a firmware for ESP8266-based smart switches called ESPurna. The firmware integrates with Alexa, Domoticz, Home Assistant and about any other service that supports MQTT or HTTP REST APIs. It supports a variety of devices, including almost the whole Sonoff family by Itead Studio, but also some other commercially available boards and light bulbs, and open source hardware projects as well.
But sometimes you just don’t find the proper hardware for your specific case. Maybe it doesn’t expose enough GPIOs, maybe it’s short of analog ports, maybe you need a double-throw relay,… Sometimes we manage to work around these limitations of the hardware adding peripherals or using a thin iron tip. But other times the problem is that it just doesn’t fit.
And size was the main reason I started creating my own smart switch board.
One might think that one of the typical uses for a smart wireless switch (like Sonoff devices) is to be embedded behind a normal wall switch so it becomes a “smart” wall switch. It may seem obvious but it’s not that straight forward. There are several things that get in the middle.
Most (all?) the boards have momentary push buttons while wall switches are (normally) toggle switches
Most of the available boards in the market are SPST, even those with SPDT relays often only provide terminals for COM and NO, not NC. I only have one one-throw switch at home, all the others are one-way-two-throw and are being used as part of a multi-way switch.
First problem can be easily solved in code. Instead of detecting one edge of the button signal (usually the rising edge since most push buttons are configured with pull-ups) you can detect both edges.