Tuesday, June 21, 2011

Finally the schematic I promised and some notes

Here is the schematic of how the Current Sensor interfaces to my Solar Batteries and the Arduino monitor. It is very simple, just an 8 volt DC supply for the Current Sensor and a limiting resistor in series with the output to the Arduino inputs.

The current sensor is a hall effect device with an output of about 32 mv per Amp. As both positive and negative current is sensed the output sensor voltage is about in the middle of the current sensor supply voltage with zero amps.   I will use an Op amp in the future to optimize the output range and sensitivity. Zero amps to/from the battery is about 4volts. As my solar panels will only output about 30 amps to the batteries on a sunny day (32 x .03~ 1volt) the Arduino analog input will be right at FS or 5volts. The battery discharge is max at about -60amps. Arduino input about 2volts. The Current Sensor saturates at +- 72 amps.

I have now added a SDdata logger shield to the Arduino solar monitor  and will soon add a second current sensor for the 240 inverter power usage. This will enable me to track/log all power for the whole system. Solar power in, the battery stored energy and all power out (household and other DC).  I can log most household items electrical usage just by inspecting the current monitors and their derivatives. more on this later.