For wearable devices, attaching them to an arm or leg can be an annoying process since the straps used often have complicated tightening/locking mechanisms. This is what inspired one Instructables user who goes by The Puma to create the AutoStrap, a self-tightening strap system for wearable electronics similar to Marty McFly’s power-lacing sneakers in Back to the Future.

The AutoStrap works by using a 3D-printed arm that is loaded with a spring and is actuated with a stepper motor. In order to check if the device is fully tightened around one’s arm, the spring contains 1K Ohm resistor within that goes from the rated resistance down to zero when the end is reached. This value, in turn, tells the Arduino Uno that a home point has been reached and to stop, where a button press can then reverse the process.

Besides being a quick way to attach wearable devices for fitness or VR tracking, the AutoStrap also has potential to become an assistive device for those who might not be able to use traditional attachment mechanisms. To read more about this project, you can visit its write-up here on Instructables and watch its demo video below.