Can any one point me to (ideally) a sensor board or circuit I could use to sample and count LED impulses from an EDMI Mk7C Smart meter ?
This meter has an LED on the front face that flashes at a rate of 1000 per Kw/hr. I can count these and measure the interval between them to get a meaningful indication of power consumption in close enough to real time. I think this means being able to detect the same level of light intensity, “tuning it”, could be important as would consistent measurements given the timing requirements.
I have an existing network of sensors monitoring and controlling a cabinet containing a HiFi amplifer using MQTT over in-house WiFi, and would prefer to continue to build on that, so I am not considering LoRa or TTN etc at this stage. The WiFi aspects suggests the ‘W’ variant of either a Pico or a Zero to keep things consistent plus I have spare ones.
I think the problem is similar to (at least part of) this topic, although the focus was more on the LoRa aspects: Kit required to connect microcontroller to Rasbperry Pi server
Hi @Andrew121107 - welcome to the forums 
I’ve seen people do this project in the past using a Light-Dependent Resistor (CE09439) in a voltage divider configuration as an analogue sensor.
You could also use a digital light sensor (CE07692).
It would be up to you to figure out where the pulses are and reject eg. ambient light - though I am sure there are clever ways to do this with eg. moving average filters or other signal processing techniques. Ambient lighting will likely introduce a slowly changing offset, but you will be looking for sharp changes of a consistent amount (based on the brightness of the pulsing LED)
Obviously, the better you can reject changes in ambient light, the more robust the sensor’s reading will be.
Cheers - thanks very much @Michael - the LDR looks like it might be the way to go. As appealing as the PicoDev sensor is, shielding it from ambient light might be a challenge. The LDR, on the other hand, could be “McGyver’ed” into a suction cap or similar I think
FYI, there’s a promising instructable that you might want to check out that uses a phototransistor as the sensing element.
I also found some retail offerings after very light research.
https://docs.openenergymonitor.org/emonpi/pulse_counting.html
