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How would you make a visual notification system for when the mail comes? Answered

We have a long curving driveway so you can't see the end where the mailbox is. We end up checking the mail a couple times a day if waiting for something important. I've always wanted to do up some kind of thing where a light comes on when the mail is delivered by way of a switch that is turned on by the action of opening and closing the mailbox. Problem is that the mailbox is a good hundred feet from the nearest window on that side of the house (which is where i'd like the light to be)
A wireless setup would be nice, but probably more complicated. Power down by the mailbox is available but house power for the driveway lights.


The system used in commercial products is a small radio transmitter/receiver, where the transmitter's power runs through a mercury tilt-switch. The transmitter gets attached to the mailbox door so the tilt-switch closes only when the door is open; that turns on the transmitter, which sends a signal to the receiver, which sounds an alert and/or turns on a light until it is reset.

Of course the DIY version could be wired rather than using the radio link; it would be a low-voltage loop (like a doorbell circuit or the low-voltage yard lights) . It actually wouldn't need much more electronics than a power supply, a latching relay, the mercury switch, the light, and a pushbutton to break the power to the latching circuit for a moment to reset the system.

remote wireless dorbell springs to mind - it wouldn't 'latch' on to keep saying there is something new but would notify when it arrives...

You could improve this by putting a relay that switches on a light/LED once the receiver would trigger the dorbell.
But the dorbell was the first that sprang to my mind, too. But having a circuit that keeps the light permanently lit would come in handy.

You inadvertently answered the question right there -- a latching relay :)

I like this but i'm not sure about the range for wireless doorbells, the button and relay switch would be around a hundred feet from the ringer part.

My parents in law use such a dorbell and the signal has to go through multiple walls. I think the distance between the button and the bell is about 30-50 feet. So I guess you could at least give it a try (I don't recall how expensive that thing was though).

What about a wireless Webcam mounted inside the mailbox, with an LED (a few milliamps at 3V) for illumination? The scene processing would be minimal -- the camera always sees the plain bottom of the mailbox; if a frame comes in that is not the plain bottom, your computer alerts you.

A bit more complex than I was looking for but great idea.

If you can run 2-core wire to the letterbox, then would a simple pressure plate inside the mailbox work?

Connect a light bulb to a 9V battery, then cut the cable, and separate each one on a piece of cardboard, with some thin foam to separate them

When the mail falls into the letterbox, the weight of the letters pushes the plates together, causing the two cables to connect and complete the circuit, which turns on the light.

Your idea seems the most simple but I don't know if I could make a pressure plate that is sensitive enough to register a single letter without giving false positives. Also, if there is mail waiting to go out, this method would register that as well and it would be impossible to differentiate between when the mail had been picked up and come because you would have to catch the light turning off and on again a few seconds later. this is why I was leaning toward a switch based on when the mailbox door is opened and closed.


7 years ago

You could use a switch connected to an XBee if you want it wireless.