I have shutters, which occasionally get blocked as something stands or leans right at the window. If the shutters are closing in, the obstacle causes the shutter to move down unevenly and it hangs loosely. Normally this chaos is solved by just opening the shutters again, but sometimes it Needs a bit more effort to get the shutter running as intended.
So, my question is this: Does anyone have or know of some light barriers or other sensors, which can block the shutters, if they identify something blocking the way?
If there is room, you could probably mount a sonic distance sensor aimed down at the window. I just read a project in the current issue of MagPi entitled Mesmeric Mirror that used a LIDAR Laser system to control LED lights along the sides of a mirror. I can find a link to the article itself but the full magazine is available here.
There might be some way to measure the tension on the strings and if they go below a certain tension you know something is blocking the shutter.
A camera with some OpenCV programming could probably pretty easily determine if something is in the way.