Lately I’ve been quite busy with the ESPurna firmware. It’s growing bigger and gaining some momentum. It’s really fulfilling to see other people using it and reporting back. But at the same time it’s very time consuming. Last Saturday I released version 1.5.0 with some new functionalities and bug fixes and I decided to use some of my free time over the weekend to work on a project that’s been waiting for a month in the shelf.
A few weeks ago I was playing with the Sonoff TH and I wrote a post about its sensor interface and the possibility of using lots of different digital sensors, including I2C sensors since the board can be easily hacked to export 2 digital pins over that interface.
And having I2C not only increases the number of potentially usable sensors but also opens the possibility of using I2C Analog to Digital converters to overpass the lack of analog inputs in the device. Here it comes the Texas Instruments ADC121 (datasheet), an 12-bit precision ADC with I2C support priced 2.74€ in quantities of 1.
The HLW8012 is single phase energy monitor chip by the chinese manufacturer HLW Technology. It features RMS current, RMS voltage sampling and RMS active power with an internal clock and a PWM interface in a SOP-8 package. You can buy it at Aliexpress for less than a euro a piece and the necessary components are fairly easy to source and quite cheap.
All in all it looks like a great IC to include power monitoring in your projects. I guess that is why Itead Studio chose it for the Sonoff POW, one of their newest home automation products. And of course I have a POW here in my desk and I’ve been playing with it this weekend. The goal is to support it in my Espurna firmware but first I wanted to know more about the HLW8012. I’ll write about the Sonoff POW in a different post later this week.
Some days ago I posted about the RFM69 to MQTT gateway based on the ESP8266 I am working on. Over these days I’ve been fine tuning the gateway at the same time I was migrating one of my home sensors to Moteino: the Door Monitor. The previous version was based on an XBee radio and has been on duty for almost 3 years and a half. Real life battery time has been around 3 months for a CR2032 coin cell, which is not bad at all, but still…
Aside from using a Moteino and a RFM69 868MHz radio instead of the XBee, I have reduced the components list by moving hardware logic to software logic. This means using sleeping capabilities of both the ATMega328 and the RFM69 and coding in a clever way to reduce awake time.