Build A Mailbox Alarm That Sends You A Text Whenever You Get Mail

If you've ever checked the mail repeatedly only to find it empty, or your mailbox is a good hoof from your house, this project is for you. It's a simple photo-sensitive alarm that will fire off an SMS message to your phone when the mailbox is opened and the sensor is triggered.

The video above shows you how it works. While it definitely requires some specific electronics to make it work, it's nothing you can't do easily with a little effort. Here's how Instructables user nikoala3 describes it:

The device uses a photoresistor to detect the light levels in the mailbox. When the light is above a certain threshold, the Arduino knows the mailbox is open. There is a red button on the front of the device that you press to arm it. After you press the button, the next time the mailbox is opened, presumably by the mailman, you will get a text. It will not send you a text again until you have armed it again. This ensures that you don't get a text every time you open the mailbox. Every time you pick up your mail, arm the mailbox phone alert and enjoy instant mail notification.

Preliminary advice: Inform your mailman of your contraption so that he does not think you have a planted a bomb in your mailbox and use a non-metal mailbox for good cellular connection.

We'd reiterate that last bit too — might want to let your postman know there's a sensor in the mailbox so they don't freak out and you find a bomb squad about to detonate your mailbox.

Beyond that, even if you're not obsessive about finding out when your mail arrives, a tool like this could be a good way to find out if someone's snooping in your mailbox that's not the mailman. Combined with a small camera, you may even be able to catch mail thieves in the act. The possibilities only go up from here. Hit the link below to see how the whole project was made and what you'll need to make one yourself.

Mailbox Phone Alert [Instructables]


    Who actually has a mail box that the postman has to open to insert mail into in Australia and is that even allowed?

    After a brief bit of research, nope, Australia Post requires an "aperture" i.e slot or else they can refuse to deliver your mail, full details are on the Australia Post website but here is an excerpt:

    Horizontal aperture At least 230mm X 30 mm. At least 130mm above internal base
    Vertical aperture At least 330mm X 30mm. At least 40mm above internal base

    Elevation of aperture above ground level
    Single mail box – between 900mm and 1200mm
    Group of mail boxes – between 600 mm and 1600mm

    Just to top it off you are lucky if the postman even takes enough care to shove the mail through the slot, half the time its just thrown in the mail boxes rough direction.

    Last edited 27/09/13 11:22 am

    Looks like I have a non regulation mailbox go me. Thanks LH I was actually thinking of setting something like this up the other day on one of my monthly trips to the mailbox :)

    Combined with a small camera,
    If you're going to stick a camera in there, why the hell are you messing around with photo sensitive resistors ? Simply put some motion sensitive software on your PC that will email/SMS you when the scene changes.
    Given mailboxes are not exactly bustling centres of activity, you wouldn't get that many false alarms. Use a wireless camera, and a solar charging panel to supplement the 9v battery, and you have a long lasting sensor - handy if your mailbox is a fair distance away.

    Personally, I would have used a mercury or magnetic switch with this method. Unless your mailbox is light proof, it's still going to get triggered by any light leakage.

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