Beam sensor or other switch needed for electric blind project
I would use a Proximity sensor of the type.


A reflective IR sensor that detects if there is a object in front of it. It contains a infrared LED and a infrared light detector and the detector detects the reflections from the LED.
At DigiKey you can find several hundreds of different versions DigiKey
A Hall transistor (Detects magnetic fields) and attach a magnet to the blind.


Reference to proximity sensors Wikipedia