Automatic blind hooked up to existing projector screen

Picture of Automatic blind hooked up to existing projector screen
Hello my name is Chipsy,
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.

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Step 1: "Reverse" engineering the projector screen motor controller

Picture of
The existing controller for the projector screen is an integrated circuit that drives the screen motor.
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 )

Picture of High level shifting ( 12V detection circuit with arduino )
The idea with this circuit is being able to "sense" with the Arduino weither the projector screen is going UP or going DOWN.

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.
rlarios2 years ago
Well done ! If you are a girl, I am impressed that you got to accomplish all this by yourself. I know many guys -self proclaimed geeks- who would never dare to do what you did !
Chipsy (author)  rlarios2 years ago
Thanks for the comment !
I'm Sorry (or not) i'm not a girl, the pics of my gf in the Valentine day's project may have fooled you !
Side note, I never meet a girl who is not from the internet and does electronics ...
rlarios Chipsy2 years ago
I'm still impressed as I haven't gotten started on Arduino myself!

I have done a few projects with MicroChip's PIC 8 bit conttrollers and your project sparked a few ideas in my head. I've noticed that most people here do stuff on Arduino and such articles are the ones with more views.

Thanks and keep up the good work.
Andsetinn2 years ago
Very nice, and the most important thing in any project, it works.
It might have been easier to have the screen relays turn on relays for the blinds for driving the blinds up and down. Then use switches that measure the thickness of the material on the blind to act as end switches. Or, since you are using Arduino, to count the revolutions of the blind core.
Can you show us the installation of the motor in the blinds? Or brand of blind if the motor is factory installed?
Chipsy (author)  Andsetinn2 years ago
The motor is a RC servo modified for continuous rotation, i removed the right original mount from the blind and installed the servo straight to the blind using screws / glue.
I shall take a picture of the motor setup if you want, but it is rather hacky :D
So that's why you must have the Arduino. To act as servo signal generator.
Have you thought about attaching infrared receiver to the Arduino to get it to read the signal from the screen remote? If you get one of those ultra-small and cheap Arduino clones you could have everything in very small package with very little wiring.
Chipsy (author)  Andsetinn2 years ago
Yes i plan to embed a microcontroller so i can remove the need of my arduino in the project, and throw everything in a little box i can hide.

I didn't tough about infrared receiver, that is a good idea, but i wanted to control the whole thing with the RF remote of the screen.
bdesigned2 years ago
Very nice instructable. I hope you will follow up with the code, I want to use this to operate the gate for my animals. Thanks.
Chipsy (author)  bdesigned2 years ago
Thank you very much ! I added the code, i took the time to rename some variables and add comments to it, hope it will be useful to you !