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Hardware
Here's the hardware I'm using in this project. With some tweaking, the project could apply to a wide range of hardware, sensors, data, functions, alerts, etc.
The brains of the operation
I had started with a Seeeduino GPRS, which has some of these same benefits, but I couldn't get it to talk to Thinger.io, my choice for an IoT website. After I think I damaged that board with electrostatic shock, I switched to the MKR GSM, which is a similar, but newer board with several benefits over a typical Uno compatible Arduino:
- Smaller form factor
- Built-in battery backup with automatic switching
- Onboard Real Time Clock for precise sleep/wake timing
- Larger memory for programming - this sketch would just about max out most Arduinos, and the relay dispatch isn't in there yet
- Hardware serial for communication with other devices without the cpu overhead of software serial
- Low energy consumption and low energy sleep (I have only seen about 10% reduction in power draw when sleeping, so I don't think I have that figured out)
This provides several data points and have its own alarm settings that can be passed along to the internet via the Arduino
- Current
- Voltage
- State of Charge (SoC)
- Alarm
- Relay
One of a very few charge controllers that can charge a small 48V battery bank. I initially had a MidNite Classic 150, but the KID [30] is much more appropriate for this small system with a small physical size and small self consumption. This provides some similar data points to the battery monitor. I probably don't need to connect both, but I plan to use the PV availability to dispatch loads (which could also be done directly from the charge controller or from the battery monitor) and to tell the Arduino whether it's summer or winter to determine full vs limited operation.