Knowing your power usage is incredibly useful information when it comes to implementing energy saving measures. With the Internet of Things slowly but surely finding its way into every possible gadget, your electricity bill will drop as the house you live in gets smarter. The day of the smart home is still a pipe dream for the average consumer but the fact you are reading this Tindie blog means you don’t have to wait! For the next few years ‘Smart’ homes will consist of engineers cramming sensors all over the house and hooking them up to a WiFi or Bluetooth radio. Followed by bragging to anyone that will listen about how hi-tech their house is.
Now that you’re filled in on the smart home situation, let’s take a look at the NodeMCU energy monitor board made by Whatnick Inc. NodeMCU is open-source firmware that runs on the ESP8266 WiFi chip. It allows you to program the ESP8266 using the LUA programming language, which is easy to get started with. There are a boatload of examples over on the NodeMCU website to get you going. All of this combined with the ADS1115 Analog to Digital converter from Texas Instruments gives you an Internet connected mains power monitor.
Power usage is calculated by multiplying current times voltage, so you must sample both of them at the same time. This board comes with a clip-on current transducer for measuring current and an isolation transformer for sampling voltage. The obvious advantage of buying a pre-designed PCB is you reduce the risk of making a mistake and letting mains voltage get somewhere it shouldn’t. Like your heart for example.
Whatnick Inc has some great example usage over on the documentation page. Using the ESP8266 it is a couple lines of LUA code to send your mains power usage over to ThingSpeak for graphing.