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Monitoring PV Generation and Grid Usage

Having recently had solar PV installed I wanted to monitor how much I was generating and match that against what we were drawing from the grid

The meter that measures the solar PV generated is the same sort as the meter that measures my grid usage. They both have a led on the front that flashes 1000 times for every unit generated/used.

I'd seen on the internet that other people were monitoring their electricity usage by counting the flashes.

I bought the dual counter module from hobby boards. I use one counter for the PV and one counter for the grid

This is the circuit I use to detect the led flashes

Basically a light dependent resistor forms one half of a potential divider which feeds into an LM339 comparator chip.

The reference voltage for the comparator is provided by a fixed potential divider comprising of R1 and R2.

Initially R3 was a potentiometer that I could tune until D1 flashed in sync with the led on the meter

OUT1 is then fed directly into the 1-wire counter

The whole thing is duplicated to provide 2 independent flash detectors.

The light dependent resistors LDR1 and LDR2 are connected by flying leads so that they can easily be mounted in front of the electric meters

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