One of my first posts on this blog was regarding a 3 Phase Smart meter I had designed in my first 1st year of University. It was meant to be used within a network of many such meters to conduct thorough power grid analysis. It had a powerful DSP on it capable of receiving samples from 3 synchronized ADC’s, perform FFT analysis if required and then forward the data to an ESP8266. The ESP was being used a simple but high speed Wifi bridge.
Since completing the project, I always wanted to do a simpler meter for the home. The idea for this was to get rid of the 2 of the 3 channels, add a relay an design a smaller PCB. This together with some decent software would turn this into a fairly capable SMART energy meter for home use.
In the 2nd year of University we were put in groups and asked to come up with an idea for a Project. I proposed the above to my team and they agreed. I was responsible for the complete hardware design and some of the software design (Websocket framework etc).
Here is what the PCB i designed look like. I was pretty happy with how compact it all looked in the end:
The idea for the case design was for it be be as compact as possible. So the case was designed around a cheap and dodgy 3 pin through you can buy off ebay for £1. The through was dissembled, and wires were attached to its contact either side, these wires were them connected together via the meter giving it the ability to turn the switch on/off:
The meter was powered by the socket and would appear on the network. There was a websocket and websever running on the network that would receive, store and plot data from each meter on the network. For fun I added a “oscilloscope” mode where the ESP was pushed to its limit, streaming live samples as fast as possible:
Here are some results when compared to a Hameg power meter, these are pretty much straight out of a uncalibrarted meter:
|Test 1: Resistive Load A|
|Voltage (V RMS)||229.16||227.19||0.8%|
|Current (A RMS)||4.184||4.1||2%|
|Test 2: Resistive Load B|
|Voltage (V RMS)||222.49||223.76||0.56%|
|Current (A RMS)||8.195||8.01||2.43%|
|Test 3: 45W SMPS|
|Voltage (V RMS)||231.64||230.62||0.44%|
|Current (A RMS)||0.427||0.414||3%|