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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    15 Discussions

    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.

    5 replies

    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.

    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!!


    About three years! Just kidding. I had a hard time to figure out how to make a switch that would turn on a light and have it stay on when the door was closed. Once I figured out the clothespin trick, it took a couple of hours. I had to mount the various parts, find a way to guide the wire (a small tube), and waterproof the battery compartment. The only flaw in the present arrangement is that the wooden clothespin is exposed, and when it rains, the damp wood conducts electricity, albeit not very much, so the LED stays dimly lit in the rain. I think a plastic clothespin would do a better job, but I haven't done that yet. I have to buy a plastic clothespin somewhere. I'm working on an Arduino project with RF communications to transmit a message to a receiver in the house, I just got the RF comm to work today. I'll probably use the clothespin trick to trigger the radio message.


    A) a
    mailbox is considered to be “leased” to the USPS for their
    exclusive use, you can do anything you wish to it's design just so
    long as it meets regulations as to height, placement, size etc.
    That's why you see old Harley gas tanks, wooden birdhouses, etc. put
    up for such use. No other matter may be placed in it, and the heavy
    penalty regulations pertain to the willful destruction or tampering
    of the contents.

    Total agreement, the delivery person has the right to refuse service
    if he/ she feels they are being placed in jeopardy.

    2 replies

    Thank you for your review of the Intricacies of Mailbox Law and for affirmation of my very first Instructables project! On close examination of the photographs of my mailbox signal system, you will immediately see that:
    A) 100% of the components of the system are "outside the box", as it were,
    B) When I showed the system to my mail carrier, he was thrilled to be able to use it. Also, all of the substitutes seem to be OK with it.
    Thanks again for your affirmation!

    You're welcome stannickel. I once had a similar situation and wanted to contrive a signal whereby when the box was opened, a flag would pop up, visible from my front window. Since I moved, it is no longer needed, but I can see the potential for this by many, well done.

    I like the idea, and have thought about some similar ideas for our mailbox, about a hundred yards from the house, but out of sight.
    Please tell me you talked to you postal workers about this though. . technically mailboxes are federal property and A) it could be construed as vandalism (hefty fine and potential prison time) and B) If I was a postal worker and saw some circuitry that looked like a trigger system I would flip out and call local law enforcement.
    But! if I was aware of what it was I would think it pretty cool .

    Again, I do like it, and it's a good idea, I've been toying with hooking mine up with a remote doorbell chime so it'd chime and turn on a light inside when it was opened.