The planned Arduino based Solar PV and Hot water monitoring and logging system were found to be very unstable and despite repeated attempts and several code rewrites we had to give up on the Arduino-based solar logging system and have decided to use the Android-based IOIO interface board with a dedicated Android Tablet and app to record the data and log solar energy generation and usage.
The IOIO board has a number of inputs and outputs which can be configured as required. Using a custom PCB (shown below) to interface with our existing solar sensors and inputs.
The new PCB has 3 pin inputs for the A/D converters and to use the existing 5V inputs a voltage divider has been added to each input.
There are 4 x 4-way headers for the I2C inputs for the temperature sensors and also the light sensor. The existing main's current sensor code will either have to be ported to Android or we will use an alternative way of monitoring the main's current input to the house.
Base view of the PCB before the components are added.
Surface-mounted caps and voltage divider resistors are on the left. We found an error with the PCB layout while building and had to add some links to correct this.
The top view of the completed PCB with the IOIO board added via headers and spare unused pins are linked to extra holes for future expansion.
Side view showing the power supply and I2C headers with pull-up resistors.