Learn how to build a NFC tag activated lockbox for a beer crate!

You open the latch, place the beer crate inside, close the ledge and scan the NFC card on the NFC reader. This activates the servo motor inside, to rotated half a circle and move a bolt in place. The box is now locked from anyone trying to steal your beer!

As a beer lockbox specifically its application is found in student housing but also in, for instance, households with young children. However you can use the principle of this box to lock away anything!

We want you to know that the placement of the components within the box is open to your own interpretation and no exact measurements will be mentioned.

Step 1: Recources and Materials

Parts and tools

Parts

MDF wood plate 9mm (950x850 mm)
MDF wood pice (approximately 50x200 mm)
Arduino uno
NFC module rfid-rc5222
NFC tag
Buzzer
Servo motor
Powerbank
14 Wires
Bolt lock
Screws
2 hinges
Metal wire (approximately 80 mm)

Tools

Soldering Iron
Screwdriver
Optional: Laser cutter
Wood glue
Double-sided tape
Laptop
Arduino usb cable

Step 2: Box Assembly

This part is optional you can also use an existing box or build one yourself.

Requirements: MDF plate, wood glue and screws

Download the vector drawing of the box and laser cut it.Assemble the box by applying wood glue on the edges. Use two hinges for the lid, glue and screw the hinges in place.

BeerLockBox2DDrawing.DXF
Download

Step 3: Programming Arduino

If you have an existing box or made your own you can start here.

Requirments: NFC shield, Arduino Uno, Buzzer, Servo Motor, 14 wires

Start by soldering the connectors to the NFC module if this is not already the case. Wire everything in place as shown in the diagram above. Ensure the wiring to the NFC module is long enough to place the Arduino and Servo motor inside and the NFC shield on the outside of the box.

When everything is connected upload the code to the Arduino. Open the serial monitor and scan your NFC tag. Probably the serial monitor will say:" Tag number: ######## NO BEER FOR YOU!". This means you will first have to authorize your tag. You can copy the tag number and insert it in the code here:

long allowedtags[] = {########};

byte allowedtagsCount = 1;

Then upload the program again. This time the serial monitor should say: "Tag number: ######## CHEERS!", and the servo will move.

NFC_beer_lockbox_code.ino
Download

Step 4: Connect Servo and Bolt Lock

There are several options for this connection one is explained below.

Put one end of the wire into the hole of the round ‘servo top’, and bend the wire 180 degrees. Attach the round servo top (+wire) to the servo. Drill a tiny hole in the side of the bolt of the bolt lock. Bent the other far end of the wire 90 degrees, and put in in the tiny hole in bolt lock. Make sure this far end stays in the hole by applying some duct tape.

The arduino makes the servo turn 180 degrees. Ensure the bolt lock is in the ‘unlocked’ position at the starting point and in the ‘locked’ position after 180 degrees turning.

Step 5: Bolt Lock Assembly

The following step will explain how to put the bolt lock in place.

Small piece MDF wood, wood glue, screws, servo motor, gear, double sided tape, metal wire, bolt lock.

Saw a small (<9 mm) ledge from the mdf. On the wall across from the hinges the small ledge is glued in placed as close to the top edge of the box as possible. This will later serve as the counter resistance to the lock.

Next a piece of wood thicker than the distance measured from the top edge till the bottom of the ledge is needed. This is used as a thickening on the lid to attach the bolt lock onto. In this example this piece is approximately 5 by 15 cm. When glueing the thickening in place, ensure that the thickening on the lid is close to the counter resistance but can still pass it when closing the box.

The distance the bolt in the lock travels is the same as the diameter of the gear on the servo motor. Keep this in mind when placing the the bolt lock on the thickening. Also when screw or glue the bolt lock in place ensure it reaches the counter resistance but can pass it when the box is being opened. The servo motor can be taped in place on the thickening as well.

Step 6: Last Assembly

Lastly, the arduino, power bank, breadboard and NFC reader need to be placed.

Depending on the length of your wiring you can position them on the lid. In the example the arduino and breadboard are placed close to the edge of the lid ensuring the wiring can reach the NFC reader. To fit the wiring past the lid a small groove was made on the side. They are assembled using double-sided tape but you can also use more permanent option.