An update - I'm stressed beyond belief which sucks but the good news is I tinker/code to relax so this morning I had my 2 year old measure out two length of 2 cable and I soldered on two more current sensors then hooked them up to the hotwater tank. The run is far from permanent or professional looking(do pro's stick wires to the ceiling with ducttape?) but it is hooked up and "working"
Here is my hotwater usage since a few minutes after noon.
The first big flat usage is my shower then my wifes, both extra long and hot for the sake of scientific discovery. It took almost an hour to recover from what was probably 20 minutes of showering.
The other flat top is from the dish washer. I find the 5 needle point spikes interesting they don't line up with usage in the house that I can identify so I believe that is the tank staying warm. I'll be logging for awhile here looking to see if that is the usage. The reason I put working in quotes is that wattage scale on the left is an approximation. I have no way to verify what the tank is actually using and calibrate the sensor. I think my tank is going to use at least 5000 watts, but as I've asked in another thread I don't understand the label on the side.
Anyways I'm very happy with this progress and look forward to determining the watts used on a monthly basis and from that the $$$. The best way would be to calculate the area under the curve but since most of my readings are on or off I'm thinking just counting the minutes where it's on and working KWH from that is easiest.
I also took the time to get the filename updating each night. I went with YYYYMMDD formating as suggested. That took about 2 minutes when I calmed down and though about it.
So far I'm very happy with this project. I've spent $3 in temp sensors $17 in current sensors, $10 in cable and an arduino that you could find for less then $30 if you look hard enough. I now have temp readings from 2 rooms with each additional sensor being $1.50 and 2 lines of code work, A current reading that tracks when my woodstove fan is running, and continuous current readings from my hotwater tank all being logged to a pc from which getting that data online is commonly dealt.
Next step. will probably be getting the data online. opening the CSV file and generating a new graph each time is getting annoying. Plus I want to see realtime readings on my TV...
Not far down the road will be getting the differential temperature controller aspect of the project working. It should be easy in my mind - read the temps if the conditions are appropriate turn a pin connected to the relay on so the relay is activated. If conditions are bad turn it off. This can all be processed in the main loop every 2 seconds like the data collection.
I also need to start seriously thinking about getting a permanent board with proper connectors to pull all of this wiring together. The breadboard is getting ugly to work on with 22 wires coming to it and a crap load of jumpers to share VCC and ground.