The first unit we built for the microgrid is called Consume001, and as the name suggest, its intention is to enable convenient consumption of power from the grid. In its initial and simplest form, the unit consists of a power "inlet", in this case a 4-pole Speakon socket (plugs and sockets are probably worth a project log themselves), a DC power meter, and some 12V car power sockets (with switches).
Above is the first version we put together at CCCamp19 (turns out making a square hole without the proper tools is one hell of fun). The DC power meter is called GC90, and has a TTL port to allow reading it out with a microcontroller. So the list of possible/planned additions is the following:
- Remote readout of the power meter, e.g. via LoRaWAN
- Different power outlets, such as USB C, DC barrel connectors
- DCDC converter to allow different input voltages
- a few more "input" connectors to allow better spreading of the grid
- integrated battery backup
- complete replacement of the power meter with a microcontroller that then also controls the DCDC meter and can connect/disconnect loads depending on grid voltage
I started working on the remote readout as one of the first things. The power meter uses a micro USB for its TTL connection, which is a little weird but also makes it easy to interface. Here's the first shot at setting this thing up:
Notice the small USB plug on the left side fo the power meter. There's a chain of boards, first a USB A breakout (mostly hidden by the case cover), a level shifter (5V of the power meter <-> 3.3V of the Arduino), an Arduino LoRaWAN dev board, and an FTDI for programming. I'm currently building a dedicated PCB for that.
Right now, there are no fuses in the unit but most of these car plugs already have on in them. Still, this is high on the list, especially for the input.
The DCDC converter should be really easy in its simplest form, just putting a ready made unit between the input and the power meter.
The last idea is probably the most complicated but also the coolest in terms of what it would allow us to do. Let's see what happens...