Window blinds

Blinds in action



Blinds are great on windows, but who wants the hassle of actually "using" them? No one, that's who. I wanted a way to automate the control of my window blinds in my master bedroom. A little reasearch online brought me to these two designs.

  1. Anupam Pathak did it with an AVR and a clock radio
  2. As well as This Instructable which uses a light sensor and a Picaxe
I wanted this to be controlled from my computer rather than a LDR or clock radio so I decided infrared would be the easiest way. An Arduino which I already had laying around seemed a bit too beefy and expensive for this simple task, so I decided to get an AVR programmer or a Picaxe kit. I love the Arduino system, and really like that I can use AVR-GCC to program the smaller AVR chips directly, but I didn't want to buy a programmer. So, while I'd still like to play with AVRs, The simplicity and price of the Picaxe system, as well as its built-in infrared commands, won me over in the end.

Ultimately my design is a hybrid of the two mentioned above, with IR as the control mechanism.

Parts List

  1. Picaxe 08M Starter Kit
  2. 38Khz IR detector
  3. Futaba S3003 servo
  4. wire

I needed to cut a bit of space out of the sheetmetal to accomodate the servo, but as it happens the tilt shaft had a ~¼" hex socket on the end. The servo shaft fit directly into this rather snugly. Originally I had hoped to be able to operate the blinds electronically as well as manually, but due to the 16:1 worm gear on the twist wand this was impossible. After pulling the gearbox out, drilling the rivets and removing the worm, the servo had plenty of torque to rotate the shaft directly. All it took was some superglue for a strong enough bond.

The circuit required for this is unbelievably simple. Presented in StandardNapkinScribbleFormat™ remote controlled blinds wiring diagram

That's right kids, no resistors or capacitors. Worked fine hooked directly up. Is this a dumb idea? Maybe, but it seems to work.

Partly because I inversed the servo position values and partly because it had a cleaner look without the servo motor sticking out, I reversed the blinds in the window. It was a happy accident, since it looks much cleaner overall this way. Of course, it makes pulling the cord for vertical movement a little bit harder, but I only do that when I have to go out onto the roof to clean the gutters, so no big deal.

Even taking the starter kit into account this cost well under $20. The Picaxe kits really are quite simple, and I think a great alternative for projects in which an Arduino would be overkill, not to mention better suited to guys like me who are just getting into electronics and might not be ready for an AVR programmer/toolchain.

I actually purchased two of everything, assuming I would want to do the same thing to the other, larger window in the bedroom, but I'm reconsidering that one. I think I'll use a stepper motor on the larger window instead since I think the S3003 would be a bit overloaded with a window which weighed twice as much. Maybe a gear motor with encoder or potentiometer on the shaft for position feedback. Thoughts?

Overall I'm fairly pleased with the results. The version in the video still uses a battery pack, but I have a few 7805s laying around and will be using them with a wall wart for a power supply. Update: I soldered in a 7805 to a repurposed 9v wall wart which works nicely

How it looks with the servo crammed in

A few minutes out on the deck cutting the sheetmetal plus some superglue and it's all hooked up.

Everything connected

Servo sticking out is hidden nicely by reinstalling the blinds in reverse. Hindsight being 20/20 I may have cut out the back side of the sheetmetal even though it would stick out a bit more. Oh well.

Installed

Everything installed. Using batteries to test.

Installed

Resting gently in the cover. Not a very high W.A.F, but I only have a G, and she has her own apartment.

Here's the source. Simple as simple can be.

If anyone has any questions, comments, ridicule, or suggestions send me a message to
nebulous (at)[ SweetBeard.com ]
Also check out my Kegbot build