I was recently asked why we were in the process of designing a new Energy module. There are already 3rd party modules with pulse outputs that can be connected to our hardware. On top of that we have our own Power module providing integrated real-time and historical power metrics.
In short, we wanted to add functionality while reducing costs to provide the most useful feature set to our customers.
Based on our customers’ and our own experiences upgrading the current specifications of our Power module was a must. This allows us to cover a wider range of installations and homes while providing the best possible metrics in a single package.
Adding ability to measure both 1 phase and 3 phase electric power. The latter in both wye and delta configuration.
Increasing the amount of connectable current sensors. The new module allows up to 12 current sensors, as opposed to 8 in the current design.
Using other electronic components allowing for increased accuracy, up to 0.1%.
Connecting different types of current sensors to a module. The current Power module only supports 25A and 50A sensors while the new Energy module supports many more (25A, 50A, 100A, 200A, 400A, 800A, etc.).
Features Broad Dynamic Range (1:1000 for current, 1:4000 for energy) and higher 24 bit resolution.
Our current design features an OLED display providing real-time metrics and status info to the user. Although being a useful feature on paper it was unfortunately rarely used and turned out quite expensive in comparison with the rest of the device. Removing it, combined with replacing other expensive internal components with more efficient ones means that the new Energy module truly offers more for less.
Of course there were some additional technical motives to improve our design. A standard power meter provides time based metrics such as True RMS voltage, current, real power, apparent power etc. An advanced power meter adds frequency based parameters like harmonics of the voltage, harmonics of the current, phase shifts between the harmonics and much more. Unfortunately most of the widely used advanced power meters (ref. Fluke) are too expensive per input for residential use and rarely allow permanent installation.
We know for a fact that the information available in the advanced electrical metrics can be extremely powerful when properly analyzed. It allows a computer based system to detect multiple devices on the same circuit by looking for their individual harmonic signatures. Or what about detecting the different power consumption stages of an appliance? A dishwasher for example has a rinse, clean and drying cycle. By analyzing the specific power signatures of these cycles a user can be notified and behave accordingly. This data also allows us to provide detailed information and an oscilloscope view at a fraction of the cost a professional power meter.
Besides removing the OLED display the following hardware decisions were also made:
Replaced the expensive DSPic with a simpler 32 bit processor.
Switched the 2 stage amplification circuit for the dedicated power measurement CS5480 IC to allow for high accuracy (at high and low power), high dynamic range and high resolution at a low cost. This component features three 24 bit channels used for power measurement of which 1 channel is used for voltage and the other 2 for current. In total, 6 of these components are used for the 12 current sensor inputs.
The new processor will be connected with the 6 power measurement ICs through a high speed SPI bus for real-time data gathering. The processor in turn acts as a buffer for all 12 inputs so the data can be made available on the RS485 bus when necessary.
And so we started to design, build, code and test our new module and compare its results with a professional (and with its 5000 EUR purchase price, quite expensive) power meter and we were amazed with the results in both time and frequency domain.
We really look forward to sharing our design, schematics, PCBs and firmware so we (and you!) can start creating really cool things on top of the Energy module.
Our wiki pages feature a first quick preview on the schematics and PCBs.
Feel free to add to the discussion and let us know what you think!