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Bead Chain Gear Drivetrain and Enclosure (fully parametric)

by adgaudio Dec 29, 2012
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I was looking for something similar to close my blinds at night and open them in the day. Plan was to add a small micro controller and battery with either an externally facing light sensor or timer, and a disengagement switch to allow for manual operation.

This is a good concept to kick start my project. I'm curious, though... where does the bead chain enter/exit the mechanism? Or is this for some other project where you have a small captive bead chain just looped between the gears? If you could post a picture of how you're using this, it would be very instructive!

Did you ever add electronics to this?


Hi Sdub76,

So cool that you are undertaking a project like this!

Where the bead chain enters and exits: In the second picture (with wood floor as background), the chain enters bottom left, curls around right gear, then curls around left gear (making an S shape), then exits top right. The picture showing my fingers shows the "S" configuration. Unfortunately, I do not have any more pictures to share. I did this project a long time ago.

In terms of design, I think the ideal configuration would be to hook a stepper motor directly into the top tube of the blinds, doing away with this enclosure box entirely, but that may be difficult if need to provide electricity to the motor or if there is no space for the motor. If you used an enclosure box like this one, you would need to secure it to the wall with corner brackets or something similar.

For electronics, you'd want to use an external power supply to power the stepper motor. You might want to check out this tutorial: https://itp.nyu.edu/physcomp/labs/motors-and-transistors/lab-controlling-a-stepper-motor-with-an-h-bridge/. The other option, which I have used a lot in the past, is the A4988 stepper driver (https://www.pololu.com/product/1182). If you use a Raspberry Pi instead of an Arduino, check out this comment: https://forum.pololu.com/t/a4988-with-raspberry-floating-step-during-boot/8645.

I would love to hear about what you end up doing! Good luck :)

fyi - I just edited my reply.

Hi PaulHam,

Unfortunately, it looks like that link has become invalid. I don't have an exact link to that stepper motor, but you may want to look at DigiKey for a similar replacement. I would modify the scad file posted on github to fit any stepper of your choice: https://github.com/adgaudio/3dPrinter/blob/master/gears/bead_chain_gear.scad

You could use any motor if you modify the scad file and find a good way to bind the shaft to the gear. Good luck!

Thanks for your reply!

Do you have a up to date link or model number for the stepper motor?

I'm glad you guys are interested! I'm currently fine tuning the parameters to sizes that fit the above parts, and the parts are coming out pretty well! Once I've put the pieces together, I'll probably add a section on electronics. This will also need a mount plate or some kind of bracket to fix it in place (to the wall in my case). I'll keep you updated with progress!

In the mean time, the latest version is on github. :)

Sweet, I was gonna do something similar, now I just need to tweak some parameters :D

excellent.. I have been thinking over a design to move two blinds (one clear and one opaque) to give a window more insulation (long story, but it involves a cat door in the window) and your design is very helpful.. Looking forward to it evolve.