Dual-Pulley Blind Actuator

Creator nophead has a roller blind setup mounted behind shutters. While this would seem extremely effective for blocking out light, but the ball chain cord that raises and lowers the blind is somewhat awkward to reach – therefore a prime target for automation. The issue, from a mechanical and automation standpoint, is that the chain requires a significant amount of force to raise the blind, and ended up jumping off of nophead’s test pulley.

Rather than attempting to increase the tension to an impractical level, he instead implemented a two-pulley setup. One pulley is driven by the motor, while the second acts to keep the chain in place and is turned indirectly by the captured chain. A threaded rod is attached to the second pulley, which moves a nut back and forth to activate limit switches that set the extent of the blind’s travel.

Electronics-wise, the device uses an ESP8266 running Tasmota firmware, allowing it to be controlled via a Raspberry Pi Home Assistant setup. The motor is driven by an L6203 chip, which doesn’t have its pins oriented on a 0.1” grid. While this would be inconvenient for perfboard assembly, nophead instead used it as an excuse to revive his decade-old PCB skills, downloading KiCad and creating a rather nice board to be professionally fabricated.

The results look quite good, including a 3D-printed housing in white PLA. If you’d like to build your own, plans for an as-of-yet-untested version which can use less expensive drive motor are available on GitHub.