Need help motorizing a window shade

[DIYer]

So i have this solar window shade i really want to automate. See i need it up when the sun comes out, and down when the sun sets. If it's too cloudy out, no need to have it up then either, which is why i don't just use a timer. I was thinking i would use some type of dusk to dawn light sensing photocell to recognize if its light out, have that control a motor,.. but how to wire that to a motor, and have the motor only pull the blind so far than stop, are where i feel i'm going to need some guidance. The motor, or servo maybe, not sure which would be best, it will need to have a little torch as id guess theres a few pounds of tension (maybe 5 tops?) when i pull it down by hand everyday.
So im envisioning a little motor mounted to the wall below my windowsill, a pulley at the top, and the handle to raise/lower the blind attached to a cable that makes a big loop from the top to the bottom of the window.

Thoughts? Suggestions? Can you think of an easier ways of doing it?..


Thanks in advance for any help, I'm decent with electronics, but not with some of the specifics of this build.

 

[CocaCola]

Personally I would look for a commercial solution, it can be done by yourself but it's going to take a lot of tinkering and trial and error...

 

[(*steve*)]

I've thought of this several times in the past.

I wanted to open and close blinds on this basis. I found that the power needed to make them open/close was large compared with the power required to tilt them.

What you *may* be able to do is hang a powered wheel from the loop of cord that controls the tilt. You can then drive it one way or the other, using the weight of the motor (and possibly additional weight) to react against.

You can tell you've reached a limit of travel because your device will start to climb the cord. Some sort of limit switch (perhaps relying on tension of the other string or just the device moving upward against a stop) will be needed.

 

[DIYer]

Theres no tilt control on this solar shade, no blinds, mines more like the 3rd one in from the left in the pic..

Theres just a little handle at the bottom used to raise and lower it. No 'commercial solution' out there to accomplish this automatically based to the suns intensity, gonna have to do it myself.

I like the powered wheel idea,.. but i just had another an idea,.. in the name of keeping it simple,.. i could use gravity to lower the shade, just add a weight to bring it down, then i'll only need a motor to raise it when sun is detected. simpler, but like that isn't challenging enough, ha

 

[GreenGiant]

Using a microcontroller, a light sensor, and either a servo or motor you would easily be able to achieve this with a small string or wire connected to the weighted bar at the bottom and a pulley system