We are upgrading our DIY PV off grid system with extra panels and also a solar hot water system using a kit from http://navitron.org.uk/ with a 20 tube 58mm double wall evacuated tube solar collector on the roof and a new water cylinder and Navitron TDC3 Solar Controller to run the hot water system. The new water pump will run from our existing PV inverter and the controller will be on the normal mains supply as this uses very little current.
We plan to monitor and log data from both the PV and hot water systems using an Arduino based system which will log current, voltage and temperature sensors.
The image below shows the main components of both systems and the monitoring points for the water and PV data.
The Arduino board will use a realtime clock and also Ethernet board to allow the data stored on the SD card to be read remotely. The Arduino did not have a realtime clock fitted as standard so we made a test version using a RTC1307 - Real Time Clock IC and using sample code from http://combustory.com/wiki/index.php we where able to program the clock to the current time.
The circuit was then recreated using a surface mount version of the RTC1307 chip and fitted to a blank Arduino shield board as shown below:
Current monitoring will be performed using 30 amp rated ACS712 Current Sensor Modules which interface with the Arduino board via the D-A inputs.
The photo below shows three of the boards fitted into boxes and two spare sensors on the left.
The temperature sensors will be using MCP9801 sensors as shown in the programming socket below.
They will connect to the ITC bus on the Arduino board to log the temperatures.
As the project progresses, I will add more posts to the blog and photos.