I just finished installing a Sense monitor. An aspect of the installation I liked was the only power source I needed to hook up was already in my breaker box. It uses a 2 pole breaker. There are three cables attached to the Sense monitor - red and black are attached to the breaker. White is attached to the neutral bus bar.
I haven’t opened a Sense monitor up, but assume there is a 240VAC → 5 or 3.3VDC to power a microcontroller and other parts of the DC circuit as well as a 240VAC → 9 or 12VAC for calculating power.
I like this method because 1) it doesn’t require additional DC and AC Power sources. 2) the design/implementation fits in neatly within the breaker box.
Do you think the way Sense handles power is “the best” way? It seems simplest to me. However, there could be aspects I do not understand. Why doesn’t the OEM hw implement this type of power source?
Simple. Regulatory requirements. To put an item like that on sale in Europe, it has to be CE marked. Then bear in mind that Megni sells pretty much all over the world as well, and my understanding there is that the appropriate national certification is required for every country into which the apparatus is imported. That implies a huge cost not only for development to ensure that the design will meet every applicable standard, but accredited testing and certification to prove it. Using twin power packs is admittedly a nuisance (which is why the emonTx V3 was designed to need only one in normal use) but by using power packs that have themselves satisfied the regulatory requirements, the difficulty has been sidestepped.
As it appears that the Sense equipment is designed solely for the US market, they don’t have anywhere near the same problem.
Thank you VERY much Robert. My “dream” is to get all the houses within my neighborhood monitoring energy with the goal of conserving. I see this as the first step in getting to using more sustainable energy (i.e.: being aware of what we are wasting and to stop wasting energy…then be aware of alternative sources - like solar, wind…).
I think your work is phenomenal and wish more was Open Source. My hope is I can extend what you all have into something we use in my neighborhood (and then beyond).
So…if I buy an emonTX and emonBase, can I get to the same data Sense talks about in this blog post?? Certainly, knowing real time power usage is step one. I am practically giddy going around turning on/off devices and watching the power change…already I’m telling my family we’re not using the dishwasher rather hand washing our stuff…and emonCMS, etc. does this fantastically.
I also want to learn about stuff like device current signatures. Perhaps it is mostly for my curiosity…but I can see real uses particularly with my goal of changing behavior through interactions with energy monitoring…besides, learning is AWESOME.
The short answer is no. The emonTx has probably got just enough resolution to be able to detect “inrush” (I’m not sure how much electrical engineering you know - you might have to look some terms up) but certainly can neither process the data nor transmit it in real time to something that can. So in reality, you’re looking at a higher spec. ADC connected directly to a reasonably powerful processor, such as a Pi.
I’ve written the few odd comments here about device signatures. The principal problem is getting enough resolution to be able to detect one small device amongst many larger, and to reject external influences, such as changes in the incoming voltage (and incoming interference). The parameters that you’re most likely to find useful are power - both real and imaginary - and inrush, and even though there are regulatory limits to the harmonics that a load may generate, the harmonic content could also provide some useful information.
All in all, some very serious signal processing is likely to be needed, with machine learning riding on the back of it. And that’s probably why so many products all have limited success.
you’re looking at a higher spec. ADC connected directly to a reasonably powerful processor, such as a Pi.
Much higher, and definitely more “horsepower” than an AVR chip. (e.g. the ATMEGA 328 OEM is based on)
According to the Technical Specs part of the webpage, Sense uses
Advanced Signal Processing at
4M/measurements per second and runs on a
1GHz ARM Processor
as well as
advanced machine learning detection algorithms to distinguish one appliance from another
Thanks very much. I decided to buy an emonPi. I just wish I could buy it through digikey or Adafruit or some place within the US. I am excited to hook the emonPi up.
Again - thanks very much for your insights.