Introduction: Smart Anti-theft Mailbox (S.A.M.)

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About: I'm an Multimedia and Creative Technology (MCT) student at Howest University of Applied Sciences. I have a love-hate relationship with coding, microcontrollers and SBC's.

A smart mailbox, designed to store packages when no one is home to receive them in person.

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Supplies

  1. Raspberry Pi 4B
  2. 2*16 LCD screen with PCF
  3. RFID sensor
  4. 2 load sensors
  5. 2 HX711 load cell amplifier boards
  6. 2 buttons
  7. 3 servo motors
  8. 2 contact sensors
  9. 2 LED bars
  10. 0.8mm multiplex wood
  11. Old computer PSU
  12. Jumper cables
  13. Breadboard's or PCB's

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Step 1: Power Supply Preparation

Make sure the power supply is OFF and NOT plugged into an outlet before doing this step!!!

  1. Cut the connectors of the wires, so you're left with just the cables.
  2. Either look up the data sheet for the power supply you are using to see which cables are for which voltage, or measure the outputs with a multimeter.
  3. I'm using a Dell PCB030, the following colors and voltages apply.
  4. Yellow: 12V DC
  5. Red: 5V DC
  6. Orange: 3.3V DC
  7. Black: Ground
  8. To make connectors you can either solder the cables to a jumper cable with a pin for a breadboard, directly on a PCB or use a connection lever clamp.
  9. You only need one of each theoretically, but I find it more practical to have a ground cable for each voltage.
  10. After prepping these cables, you will need to connect the "power good" or "pwr_ok" cable, and connect it to a ground.
  11. For the last step, you have two options:
  12. Connect the green "PS_ON" cable to a ground directly
  13. This will cause the PSU to go on as soon as you plug it in.
  14. Connect it with a toggle switch/button.
  15. This will allow you to switch the PSU on and off without touching the power cord.

Step 2: Circuit

The first step is making the circuit on either breadboards or pcb's.

  1. Make sure to place resistors where needed to protect your raspberry pi.
  2. Make sure to check the voltages of the pc power supply.
  3. Make sure to connect the grounds of separate devices, i.e.: the raspberry pi ground to the psu ground.

Step 3: Code

When you have the wiring figured out, it's time to add some software.

The code for the website and the app are found here.

  1. Open the file called "index.html" with the live server to get on the website.
  2. Copy paste your raspberry pi's IP address in lieu of the live server address.
  3. It should look something like this:
  4. `http://172.30.252.17:5500/front/index.html`
  5. Run the App.py.

Step 4: Enclosure

Of course it's up to you to decide how large you want it to be, but here are the measurements I used.

8mm Multiplex wood, length and width are in cm:

  • 3 * 5x40
  • 2 * 4x38.4
  • 2 * 20x30
  • 1 * 15x40
  • 2 * 45x38.4
  • 1 * 45x40
  • 1 * 40x35
  • 1 * 40x40
  • 1 * 38.4x38.4
  • 1 * 30x38.4
  • 2 * 37x18

Step 5: Putting It All Together

Now it's time to add the last finishing touches. Choose where all your components should go, make a plan on how to route the wires, make the necessary cutouts and most of all, have fun.