Mailbox Signal System





Introduction: Mailbox Signal System

This is a very simple electric mailbox signal system for rural mailboxes. It uses a high-intensity LED, a 9 volt battery, a 330 ohm resistor and a homemade switch made from a clothespin.

Step 1: Schematic

The parts list is very simple. A 9-volt battery, a 330 ohm resistor, an ultra bright LED, and a custom-made clothespin switch. Update 6/7/2015. If you are an Arduino hobbyist, you can make a nifty flashing light with an ATTiny85-20PU chip (Cost for the chip is about $1.50 on eBay). You can program it to do any kind of blinking you like--just edit the sample Blink sketch. I made one using Morse code that says: Mail is here". I've attached the schematic for that one above.

Step 2: Mailbox Door and Wire

A hole is drilled into the mailbox door about 1 inch from the bottom and into the side of the door. A wire is threaded into the hole and twisted so that it stays there.

Step 3: Clothespin Switch

A wooden clothespin (plastic would be better for weather resistance) is modified by drilling a small hole through each of the jaws on the closed end. Wires are threaded through the holes and glued into place with hot melt glue (or any good glue). The ends protrude inside and make contact with each other. To make the contact better, I soldered a drop of solder on each wire on each side. When the clothespin is shut, the circuit is complete and the LED turns on. To turn the switch off, I put a non-conducting piece of plastic between the two jaws of the clothespin. The plastic piece is connected to the wire leading from the mailbox door and is snatched away from the clothespin when the mailman opens the mailbox door. The clothespin switch then makes contact and turns on the LED.

Step 4: Open Switch

When the plastic piece is pulled away from the clothespin, the clothespin switch closes the circuit and causes the LED to light.

Step 5: Detail of Off and on Positions

The top picture shows the clothespin in the off position. That is, the non-conducting plastic piece or insert is held by the clothespin and prevents the wires on each side of the clothespin from contacting each other. Hence, the circuit is open and the LED is off. When the mailbox door is opened, the plastic piece is pulled away from the clothespin and the circuit is closed making the LED turn on.

Step 6: Showing LED Off and On

You can see in this picture that when the LED is off, there is no light. The on position shows a very bright light. The LED must be high-intensity, otherwise it would not show up in bright sunlight.

Step 7: Privacy

Although it would be a nice service to the neighborhood to let everyone know when the mailman has passed, I felt it was not a good idea to make it too obvious. I made the LED such that only I can see whether it is on or off. The reason being that I don't want any crooks to know when the mailman has left mail in our boxes. So, to this end, I put the LED inside a tube and pointed it at my front door. I'm the only one who can see if the light is on or not.

Step 8: Conclusion

This has been a very handy gadget for me and required no deep knowledge of switching mechanisms like NOR, NAND, OR gates, etc. It's just a very simple electric circuit and fulfills the function of letting me know that the mailbox door has been opened.



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We have a flag that goes up when the door is open but i like the light better. Thank you for taking the time to make and share.

I've since enhanced it with a ridiculously silly microcontroller (ATTiny85) that transmits Morse code and sends the words, "Mail is here". Most people have no idea what Morse code is anymore.

So it sends morse code to your house saying "Mail is here"? Cool, I am a Amateur radio operator and I like morse code. Yes even ham radio has gotten away from even making the people to take the code test to get a license.

Although I have a working, pending project to use RF signals to send temperature and "Mail is here" to my house, I have not implemented that. It's messy. All I have now is a microcontroller, between the clothespin switch and the LED bulb. The bulb itself blinks the code and requires a line-of-sight view of the bulb from the house; which I happen to have.

So the message is replayed multiple times?

Over and over until I reset it. My concern is battery life. I'd like to do a really cheap solar system. Maybe gut a garden path light and use the parts. I'm just afraid that it won't handle the 3.3 volts or 5 volts and wattage requirements of the LED and microcontroller, though. I'm not ready to spend $25 on a solar panel that does the job. So far, two coin batteries typically last 2 months. But, I'm retired and get the mail shortly after the mailman goes, so it doesn't flash too long on any given day. Your mechanical system is still a good idea. This one is just more fun.

Beautiful! Exactly what I was looking for. Thanks for posting it.

You're welcome. That one has worked for over two months already and is still working fine. Just today I installed another model that has a 555 timer circuit that makes the LED blink. I'll see how long that one lasts.

I've updated my clothespin switch with a couple of turns of copper wire on each jaw to improve the contact area. Also, I soaked the clothespin in vegetable oil to make it less prone to water absorption which can cause a small flow of current during a rain shower. Mineral oil may be a better choice--it won't become rancid!!


nice- this is a really cool home automation project! how long did it take for you to make this?