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I love getting mail. It's like a surprise gift that arrives six days a week, and I look forward to seeing what I've gotten, even if some days it is only bulk mail.
But I don't like walking out to the mailbox and finding it empty. That's always a disappointment.
So I decided to add a home automation sensor that would let me know when the box has been opened, so I can rush out and see what treasures the carrier has delivered.
The mailbox is too far away from the house for a traditional sensor. Fortunately, I'm already running a LoRa network, which has a very long range (up to 1/4 mile), so I investigated the devices available from YoLink. I briefly considered their vibration sensor, but rejected using it because my mailbox shares a mounting post with my neighbor's box. And both boxes jiggle whenever either is opened. I only want to be notified when my box is opened, not theirs.
I ended up using the YoLink motion sensor instead. It's a standard passive-infrared device, but putting it inside the mailbox avoids all the usual false triggers that those devices inevitably spew. Its sensitivity to shifts in light and heat actually works in my favor, reliably detecting when the mailbox door opens.
The device comes with a magnet for mounting, which works very well for deployment inside the metal mailbox. After trying different locations, I found putting it high on the back wall works best. It's out of the way of incoming packages, and pointing it towards the opening gives it the best chance of being triggered.
LoRa signals are capable of pushing through metal, but as I wrote twenty years ago in Smart Home Hacks, when a door is open any sensor's signal can escape. But I do receive a single daily notice from the YoLink app that the device has dropped offline. That's OK because the motion trigger still gets sent reliably, thanks to that open door, so I've mostly convinced myself not to worry about the hub complaining that the device isn't constantly checking in.
An unexpected bonus of installing this system occurred during a recent out-of-town vacation. I had filed a vacation-hold request with my post office, and after a few days I started receiving notifications that the box was opened. A call to my local branch revealed that a newly hired carrier had mistakenly resumed delivery. Without those notifications, I would never have known.
Finally, a technical note: YoLink devices don't integrate with the rest of my home automation setup. I'm a firm believer in redundancy when it comes to automation, and having separate, parallel systems doesn't bother me in the least. (But there are third-party methods for integration, such as Home Assistant and Homebridge.)