Interference (from fridge) on pulse counter

Hi All,

I got my Emonpi yesterday and have successfully set it up for electricity monitoring. Everything is working brilliantly.

I have also hooked up the pulse counter (via the RJ45 connector) to my gas meter which conveniently has a reed switch (which pulses every ft3) exposed via an RJ11 connector. Making up a suitable cable means that the Emnopi counts the pulses very nicely when the gas is flowing.

I noticed overnight that the pulse count was slowly incrementing (when the boiler was not in use)

Checking the meter readings showed that the meter definitely wasn’t incrementing the display so definitely not real pulses. A bit of experimentation revealed that “phantom” pulses are coming from a camping fridge I have nearby! It’s running off 240v and has a heating element - I can reproduce the phantom pulse on demand by simply switching the element on.

Anyway, now I know the source of the interference, any ideas on how to prevent it? My RJ45-RJ11 cable is not shielded would it help if it was? Could I use a capacitor across the connectors to prevent this stray RF pulling the ATMega input pin low?

All guidance gracefully received. The number of phantom pulses is low enough not to really skew the figures too much but I’d like to solve it nonetheless.


Edit - added superscript notation. BT - Moderator.

Have you seen this thread? There are some possible remedies discussed there.