It seems like creating an automatic dorm room door opener is a rite-of-geek-passage each fall. [Adam], a student at Vassar, passed with flying colors by creating this clean setup. We’ve got video, more pictures, and a description after the break.
Above we see the device mounted on the inside of the door. The larger box houses a printer head carriage that does the physical turning of the handle. When the carriage moves from right to left it pulls a string attached to a long lever on the door handle (seen in the picture at the top of the post), providing the turning motion. Below this box is the control circuitry that we’ll look at next.
Here we have the brains of the operation. In the project box on the left is a board that takes care of the wireless fob communications. [Adam] tells us this works from about 250′, uses a roll algorithm over RF for security, and has a dedicated 12v DC power supply. In the middle is the timer circuit that controls the motor operation, with four 9v batteries providing the motor with power.
Motor control is provided by a timing circuit using three 555 timer ICs. [Adam] based his design off of a two chip delay circuit but scaled it up to three to give him more options. The circuit is responsible for driving the motor until the latch is open, holding for a set amount of time, then returning the motor to its original position.
Because he’ll be moving out at the end of the year, [Adam] wanted to make the system easily transportable. He’s used a jack system so that the controller can be mounted either above or below the motor unit at his next residence.
This works well and with the covers on the project boxes it’s not the duct-tape mess of the last door opener we saw. Nice work!