As a part of his business, element14 Presents’ Clem Mayer sells physical goods online and has people retrieve them near his house. But for the times he is not able to be home, Mayer was inspired by his post office’s pickup lockboxes to create his own version that could be accessed with just a code at any time.

Because this parcel container would be outside and exposed to the elements, Mayer went with a sturdy electronics cabinet that is IP66 rated and made entirely from metal. Initially, he was thinking of a system that would require users to scan a QR code on the box, go to a website, and then enter the code to gain access. However, the complex nature and network connectivity led him towards a much simpler solution instead- just enter the digits on a physical keypad. This way, a single code could be set in the Arduino Leonardo’s EEPROM and then compared each time a total of six digits are selected.

The PCB Clem designed contains a header for the Arduino, a 4×4 grid of tactile pushbutton switches, six LEDs at the top to signal which digit is active, and a relay for unlocking the box. The mechanism itself is an off-the-shelf latch housing a solenoid that unlocks whenever power is applied from the 12V power source. For more information about this project, you can watch the build video below or check out Mayer’s post here in the element14 community.