Receiving the packets sent out yesterday is easy – in fact, since they are being sent out on the same netgroup as everything else here at JeeLabs, I don’t have to do anything. Part of this simplicity comes from the fact that the node is broadcasting its data to whoever wants to hear it. There is no need to define a destination in the homePower.ino sketch. Very similar to UDP on Ethernet, or the CAN bus, for that matter.
But incoming data like this is not very meaningful, really:
L 22:09:25.352 usb-A40117UK OK 9 2 0 69 235 0 0 0 0 103 0 97 18
What I have in mind is to completely redo the current system running here (currently still based on JeeMon) and switch to a design using ZeroMQ. But that’s still in the planning stages, so for now JeeMon is all I have.
To decode the above data, I wrote this little “homePower.tcl” driver:
It takes those incoming 12-byte packets, and converts them to three sets of results – each with the total pulse count so far (2000 pulses/KWh), and the last calculated instantaneous power consumption. Note also the “decompression” of the millisecond time differences, as applied on the sending side.
Calculation of the actual Watts being consumed (or produced) is trivial: there are 2000 pulses per KWh, so one pulse per half hour represents an average consumption (or production) of exactly one Watt.
To activate this driver I also had to add this line to “main.tcl”:
Driver register RF12-868.5.9 homePower
And sure enough, out come results like this:
This is just after a reset, at night with no solar power being generated. That’s 7 Watt consumed by the cooker (which is off, but still drawing some residual power for its display and control circuits), and 105 Watt consumed by the rest of the house.
Actually, you’re looking at the baseline power consumption here at JeeLabs. I did these measurements late at night with all the lights and everything else turned off (this was done by staring at these figures from a laptop on wireless, running off batteries). A total of 112 Watt, including about 24 Watt for the Wireless router plus the Mac Mini running the various JeeLabs web servers, both always on. Some additional power (10W perhaps?) is also drawn by the internet modem downstairs, so that leaves only some 80 Watt of undetermined “vampire power” drawn around the house. Not bad!
One of my goals for the next few months will be to better understand where that remaining power is going, and then try to reduce it even further – if possible. That 80 W baseline is 700 KWh per year after all, i.e. over 20% of the total annual consumption here.
Here are some more readings, taken the following morning with heavy overcast clouds:
This also illustrates why the wiring error is causing problems: the “pow3″ value is now a surplus (counting down), but there’s no way to see that in the measurement data.
I’ve dropped the packet sending rate to at most once every 3 seconds, and am very happy with these results which give me a lot more detail and far more frequent insight into our power usage around here. Just need to wait for the electrician to come back and reroute counter 3 so it doesn’t include solar power production.