Motorized automatic window blinds

My latest home automation project, since a month or so ago is to automate my window blinds.

Here’s the general idea:

I want to simulate human activity in my home when I’m away. Lights are currently turning on and off, thanks to Icon relay switch, but the blinds remain shut all day long. I thought it would be a great idea to open and close them automatically, according to the time of day.

Here how I plan to make them work.

-A PIC (probably a 10F206) will be the central brain.
-A MAX4427 will be used to drive the electric motor. I know it’s not supposed to be used as such, but it proved to be reliable.
-A GM2 gear motor is used to turn the tilt rod of the blinds.
-A DS2408 will be used to interface the 1-wire network to the PIC.

The 10F206 have 4 I/O lines. I plan to have 2 of them as input and 2 as output. The 2 outputs will be forward and reverse control for the GM2. The two inputs were planned as 4 possible positions (00=0°, 01=45°, 10=90° and 11=135°).

From then, I will use the TINI to talk to the blinds, probably using xAP. This will allow for everyone that needs to to control the blinds, of for them to move automatically when it’s time.

I first tried to couple the gear motor on the shaft at the top of the blinds, but the motor isn’t powerfull enough. And believe me, higher voltage isn’t an option to give more power the the motor. The MAX4427 are already tight in their specs, increasing the voltage simply blow them away.

So the next option is to use the gearbox where the original rod was used. It places the gear motor more visible than I wanted to, but now the GM2 is powerful enough. This brings another problem though: Backlash. When opening the blinds manually, it isn’t a big deal, but because I don’t have a mean of telling at what angle are the blinds, I cannot easily rely on time to place them in a specified position. I must include a backlash compensation inside the PIC software.

I still have to program that backlash software into the pic. I think it won’t be too complicated. I should be able to do so this week. I’ll keep you informed how the project is going. I will also have a few pics and maybe a video for you later this week.

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