I'm French, reading instructables since at least 2 years, it is the first entry i make on this website.
Why i made this project :
I have a small homecinema system in my living room, with a projector and a commercial motorized projector screen.
I have a big mirror on the left wall, it makes the room brigther, but when watching a movie you want a dark room, and we could see reflections of the movie in it (very annoying) so i installed a grey/black blind i found in a DIY shop, it was a great fix.
Now i had to get it down then up every time by hand, so i tough "why not motorize it?"
Why i didn't just remove the mirror ?
The mirror is embedded in the wall, and it is nice when not watching a movie, it expands the living room. So i wanted to keep it, but still be able to watch a movie without seeing the reflections in the mirror.
Step 1: "Reverse" engineering the projector screen motor controller
It is controlled via an RF remote.
I grabbed my multimeter, and was able to find 12V on the relay coils.
So i soldered one wire to each relay coil (the terminal that gets down to 0V when the relay is "OFF"), plus one wire for GND.
Step 2: High level shifting ( 12V detection circuit with arduino )
This circuit works like this :
- When current is provided on the base of the transistor, the current flows from Arduino 5V to GND, the Arduino INPUT is then HIGH.
- When NO current is provided on the base of the transistor, the Arduino INPUT is connected to GND, and then the INPUT is LOW.
I used two transistors (TIP122), one for each relay of the projector screen.
Now i am able to know when the projector screen is going down, or is going up.