I’m working on a project were I have to build a network of battery powered sensors over a territory the size of a small town.The sensors will monitor power consumption, temperature and humidity in energy poor households. Often the families in that situation can’t afford an internet connection at home so WiFi is out of question. GPRS would be an option but lately other radio technologies have come to my interest.
I’m a core member of The Things Network Community in Catalunya. LoRa is one such technologies. The (soon) availability of affordable gateways and the open nature of the software stack (from gateway firmware to backends to handlers) make it a great candidate to build an open, libre wireless sensor network that can cover large territories with few gateways.
Someday soon I’ll talk about the gateways, backends and so. Now I’m focusing on nodes. The idea is very similar to my previous post about a Moteino energy monitor node with an RFM69 radio, but using a LoRa radio and LoRaWan protocol instead. There are several options here. The cheaper and more common is to use a HopeRF RFM9X LoRa module and implement the LoRaWan specification in code. There are already libraries for arduino and alike that implement the LoraMAC specification almost at 100%. But for my first try I used another approach.
Microchip is selling a serial module that implements the full LoRaWan stack and communicates with your favourite uC through serial. The Microchip RN2483 (in the EU) is very easy to use and it’s price is not very different from HopeRF modules (both are about 15 euros at DigiKey). It’s the same module that the people at The Things Network have used for their The Things Uno prototyping platform (and Arduino Uno with a RN2483 module).
Question is: is the RN2483 a good choice for a battery powered LoRaWan node?
November was a busy month and the Sonoff Dual that IteadStudio kindly sent me to review was bored in a box waiting for some free time. But it was just fair that another board that has been waiting in the boards-to-review box for longer had it’s chance to have some fresh air too. So here we have the Itead Studio Sonoff Dual and the Electrodragon ESP Relay Board face to face.
My daughters love to talk to (or with) my Amazon Dot [Amazon US] in their funny English: “Alexa, hello!”, “Alexa, li-on!” (actually “light on”). It’s so easy to use it to switch on/off things at home using the fauxmo python script by Maker Musings. In his post about Amazon Echo and Home Automation more than a year ago he explains how he reverse-engineered the protocol of the WeMo switches that Alexa (Amazon Echo [Amazon US] or Amazon Dot [Amazon US]) supports.
I also have a server running the fauxmo script with an MQTT handler to control some of the Sonoffs I have at home, but this morning I woke up thinking: why should I use an external script to control my devices if I can code it in the firmware?
Some months ago I wrote about a hack I did to one of my Sonoff devices to be able to use a simple current sensor to monitor my washer machine process and alert me whenever my laundry was done.
A few weeks ago Itead Studio released two new models for their Sonoff line, the POW and the DUAL. And the POW is Itead’s answer to my hack. I’m not saying they copied me, just that the Sonoff POW makes my hack utterly unnecessary. Do you want to remotely monitor your devices energy consumption? Buy a POW.
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.