[Diederich] is running a Raspberry Pi loaded up with Pimatic, a great home automation server that does just about anything you can throw at it. One thing it doesn’t do is monitor electricity and gas directly from the meter – you’re going to need hardware for that. [Diederich] stepped up to the plate and built that hardware using just a 555 timer. The total cost of adding this to his Pimatic setup was less than a dollar.
The 555 can be used as a timer, a trigger, and a bunch of them can be cobbled together into a CPU. [Diederich] isn’t using some fancy logic here; he’s just using the 555 as a Schmitt trigger with a phototransistor and his electricity meter. The output of the 555 is connected to the GPIO of the Raspberry Pi, and a Python script ties into Pimatic.
It’s a neat solution that only costs a dollar, and using the 555 has a few advantages: the 555 makes it possible to use long and thin wires back to the Pi, which means [Diederich]’s Pi doesn’t have to be located right next to his meter.