Hi today we will be making a Arduino Powered Secret Mailbox Compartment!

This design allows you to build a secret compartment that can disappear as quickly as it hides the most valuable of items (big or small) for any type of secret dead drop that a spy could plan. Plus it adds an Arduino powered feature to let you know if the secret drop has been received!

All of the other hidden compartment designs I've seen are permanent modifications to items, where this one can be moved with slight modifications from one mailbox to another. Pretty cool, right?! We hope you agree =))

Mailbox Flap Test

Mailbox Test

Arduino Alert Demo

Supplies

Mailbox

Cardbord

Scissors

4 Magnents

Black Spray Pant

(Optional) Arduino w/starter kit

Step 1: Trace Your Mailbox - Cut Out the Hidden Flap

For step this you will need to get a pencil and trace the outside of the mailbox and leave a tab on the bottom (about 1 in) and then trim the edges until it fits inside where it is snug but not tight. You will likely need to test fit this a few times to get the fit just right.

Step 2: Adding Magnets to the Hidden Flap

For this you will need to add one magnet in the middle on the bottom flap. This is the part that will hold the bottom of the flap to the bottom of the mailbox. Add another magnet near the top of the secret compartment flap. This will be the way that the flap is folded down to hide and retrieve hidden items.

Step 3: Spray Paint the Hidden Flap

Spray paint the hidden flap made of cardboard the same color as the inside of the mailbox. If necessary, paint the entire inside of the mailbox black to make it easiest to match the flap to the rest of the inside of the mailbox.

Step 4: Positioning the Hidden Flap

Place two magnets on the top of the inside of the mailbox. These will help the top of the hidden flap remain vertical. Now, place the hidden flap into the mailbox, with the painted side down, and slide it in as far back as you want. The farther back the less hidden storage, but the less likely the compartment will be noticed. The magnets on top will slide back along with the hidden flap as you push them both towards the back. With the 2 magnets on top and the 1 magnet on bottom, the only way for the hidden flap to move will be forward. Test the hidden flap by using a magnet to pull down the top of the flap. If the hidden flap is too tight to allow it to fold down, then trim the edges until it folds down with only a little effort.

Another great thing about this design is that there are NO permanent modifications to the mailbox. The magnets and hidden panel can be removed from the mailbox with no indication it was ever used for those secret spy-like dead drops that would make it a great addition to everyone's spy toolkit!

Step 5: (optional) Adding the Arduino-Powered Signaling Device

It is possible to know if the secret compartment has been accessed by using an Arduino with a electrical trigger to identify when the compartment has been opened. Using tin foil to make a metal connection, the red signaling light stays off until a person breaks the metal connection, tripping the red light to go off. The Arduino could also be programmed to send a text message to the user letting them know that the secret compartment has been opened. I can send the code for how I programmed this to anyone that would like to try this.