This amazing “pressure door” was built by artist Alan Rorie for a Nautilus-themed art car. The door features an RFID-controlled lock mechanism and a four-foot motorized iris.
The motorization of the large aperture was surprisingly easy. I used two small DC motors with spur gears and nice torque mounted on either side of the cam ring. I then welded chain around the cam ring turning it into a giant gear. It worked the first time I tried it. I controlled the two motors with an Arduino and a motor shield, two limit switches and a few lines of code. I then modified an old positioner and inserted a set of buttons, so that when you pull the handle of the positioner it trips the buttons and turns the motors.
The RFID was super easy. I got a D12 RFID reader, hooked it up to another Arduino, and used it to flip a 40A relay attached to a 30 lbs pull automotive solenoid. The solenoid was coupled to a super beefy industrial latch. The latch keeps the door closed until is sprung by the solenoid, when to door is closed it pushes the spring latch back into its locking position. Just like the trunk on your car. I love the result. The door is rock solid closed with no visible way to open it. Then you wave your fob by the reader and the door literally pops open. When you close the door there is solid, satisfying snap as it latches in place.