To avoid the build I create a new ‘fun’ project ….
The post box is a standalone unit about 6m from the house . Want to detect when it’s opened presumably by postie to delivery parcel . It does have a letter slot - but I could block that up .
First thought was a Shelly / zigbee battery door sensor . Works sometimes . Range is the issue … Also no mains power at the postbox .
So ! , maybe a Shelly relay mains powered but it would need mains which is around 20m away and then long cable to some reed sensor type magnetic switch in the postbox .
Seems like a lot of work to work out if a letters been posted !
A good / bad plan ? ; other suggestions??