Open and Close Curtains

I'm trying to figure out what parts I'm going to need to open and close a set of curtains. They're lightweight shear curtains that hang from rings along a rod.

I'm thinking of using a single motor and two gears in the middle to control each curtain. The idea is to have the gears running opposite directions and have them attached to pulley systems that are attached to the first ring of each curtain.

Couple question. First, what type of motor should I use? Should I use a simple gear motor, stepper motor, or a cheap hobby motor? The motor would need to be able to run in both directions (to open and close).

Also, and more importantly, what type of gear and/or cylinder should I attach to the motor and what's the easiest way to have them run opposite directions? Where would I acquire such a thing? I've looked around on Adafruit and Sparkfun but haven't seen any sort of gear mechanism or anything to attach to the motors to accomplish this.

The thought is to have a line run around each cylinder so when the motor kicks in it spins the lines around a set of pulleys so the curtains will move. Problem is, I have NO idea what to attach to the motor and how.

Thanks.

I'd suggest you design the hardware side using a pull cord looped around a couple of pulleys to open and close the curtains. This is how hand-operated curtain closers typically work, and you might even be able to install a standard setup - that would avoid a lot of hassle sourcing pulleys and brackets and so on.

Once you have reduced the problem to pulling on a cord, you can install a motor/gearbox/pulley combination to do the pulling for you. I was surprised how much torque was provided by a small DC motor attached to an epicyclic 200:1 gearbox - it only draws about 100 mA or so at 12V so is easily within the range of current supported by a small h-bridge driver - and has no trouble opening and closing my blinds. Your requirements may vary so I suggest you get the pull cord hardware set up, find how much force it needs to operate it, choose a DC motor / gearbox / pulley combination and power supply which produces the required force and speed, and then look for an h-bridge driver capable of driving it.

For comparison, my solution uses a Baby Orangutang Arduino with integral h-bridge, a tiny DC motor + integral 200:1 gearbox, and a cheap 12V 1A regulated wall wart that powers the whole thing. The hardware is absolutely tiny and the enclosure is mostly empty.

That's a great idea! I never thought about adding the hand-operated curtain system and modifying that. I'm guessing something like this is what you were referring to?

Depending upon the complexity of your needs, there is also commercial options to manage the opening/closing… you can interface the Arduino into this as required. Just google “electric curtain rod” for ideas.

I’m pretty big on doing projects end-to-end, but sometimes the mechanics of something interferes when the wife objects to having “that hideous-looking thing” in the house.

Ray

Well the mechanism will be hidden by static curtains on either end that won't be moving. Just the shear will be opening and closing. The wife will be fine with that (hopefully). I'm also getting my kids involved so she's a fan of this project. This will be my first dive into electronics and the Arduino. I'm starting with one of the "starter kits" so I'll initially be playing around with the LED's and the basic stuff. But soon moving on to this curtain project.

Any ideas on which specific gearbox I should use and where I can buy one? I found Tamiya gearboxes on Pololu but they seem to be geared towards robots and wheels.

Thanks for the input.

How about a sail winch servo. Easily interfaced with Arduino (no H-bridge), work on 5 V [probably need an external supply, but any motor would anyway], built in gearbox and easily sourced.

Edit: You can also position the curtain precisely in response to a light sensor or even IR remote

Indeed. My plan was to use a light sensor to have them automatically close when it gets dark and open in the mornings when it gets light. I was looking at some of the pull rods and they look like they'll work perfectly (found one that works with two curtains and opens/closes in the center). Any ideas as to how I should use the motor to actually pull the rope? I've used these before (manually) and they can be pretty hard to pull.

The light sensor (LDR) approach works fine for me.

As far as pulling cords goes, I just wrapped the cord several times around a pulley and positioned things so that the cord was under slight tension.