Landis+Gyr E470 LED Pulse Counter Sensor

I have an E470 elecricity meter manufactured by Landis and Gyr. The meter has a red LED which flashes 1000 times for 1KWhr of electricity usage.

I wanted a mount to hold a sensor to monitor the flashing LED. My requirements included making the sensor mount to the wooden base board with no connection to the meter. It hovers just above it ~1mm. The sensor also needed to be easily removeable for maintanance should it need it.

The solution I came up with is presented here.

Four prints are required for the full solution but you could trim number of prints down if you stick the sensor to the meter. I didn't want to do that.

The sensor is one of the cheap chinese sensor PCB's like this with a LDR (Light Dependant Resistor)  :-

It's what I had on hand and worked really well. The meter flashes the LED and it's bright this is usefull as the meter also has a backlight which can be seen through the same opening in the meter as the consumption LED flash. I was able to adjust the potentiometer to descriminate between the LED flash and the backlight which sometimes comes on on it's own. This is important to not count the backlight as a consumption flash. In addition, to make the sensor enclousure a bit smaller I removed the 4 way 0.1" pin header to save some room and hard wired the 3 connections required (G = Ground, += VCC @ 3.3v, D0 = Digital Out).

The sensor housing uses 3x M3 machine screws and brass inserts (cheap chinese ones). Should you build the standoff like I did the standoff requires 2 more M3 screws and inserts. I possibily could have optimised the mechanics better but I wanted to try brass inserts :-)

I used a bit of hot glue to fix the sensor PCB to the Meter_LED-Body ensuring the LDR is over the hole so it can sense the meter led. There is a small hole ~1.75mm on the lid where you can poke a bit of clear filament so it touches the sensor LED that flashes when triggered by the meter. When I built mine the hole was a bit small so I scraped the filament with a scalpel until it fitted and just poked it in unill it stopped. I then trimmed of the excess with a scalpel.

Instructions,

If you are willing to glue the sensor enclosure to your meter, you need, 3x M3 screws plus brass inserts. Print Meter_LED-Lid and Meter_LED-Body . No suppots are required and I used black PETG @0.2mm layer height. Fit the sensor and away you go. You now have a sensor to monitor your electricity.

If you want to add the holder so the sensor can be removed, print Meter_LED-Holder. This will require supports for the two retaining clips. I used tree supports so there was no marks on the print. In thory the holder can be glued to the meter but I did not want to do that. A nice thing about the holder is that you can align the meter LED with the hole in the holder to ensure all is aligned correctly. I printed mine in black PETG @0.2mm layer height.

Lastly, if like me you do not want to sick anything to the meter body as it belongs to the electricity folks. Make the standoff (Meter_LED-Standoff). The standoff is 70mm long as that is 1mm more than the meter face to the wooden backboard of my instalation. You mileage may vary here so you need to check and figure out if it will fit. The print requires supports and I used tree supports to save marking the print. There is extra hardware required to mount the support to the holder. (2x M3 screws plus inserts). I assembled the holder+ standoff and then placed it on the meter backboard moving it around untill the LED on the meter was perfectly aligned to the hole in the holder. Then I used 2 small wood screws to fix the standoff to the wooden backboard.

The output from the sensor is connected to an ESP32 and using ESPHome. I setup a system to report back to Home Assistant. Shoutout here to the ESPHome and Home Assistant folks who have done an amazing job. Another shoutout to the Freecad folks who have produced something very workable with version 1.1. 

When in use you can see a dull red glow to indicate the sensor has power and a brighter flash when it detects the meter LED.

I used this project as a driver to learn more Freecad and I'm happy with the result. Again I made only one of these so have not tested it on any other kind of meter. If you can make use of this for your own project, great.

PS. The usual caveats about messing around near high voltage electricity apply. If you don't know what you are doing stop.