SparkFun Forums

[krkeegan]

In short I am building battery powered electric blinds. This is to be used on cheap cellulose blinds that weigh next to nothing. I see plenty of motors or stepper motors that look like they would provide sufficient pull strength.

But what can I wind my string onto? I think I need a small plastic spool that mounts to the axel of the motor, but I can't seem to find anything like that.

Any ideas?

[bsagan]

Yoyo.

Well 2 or 3 yoyos. You will have to pull the blinds up from both sides (for sure) and possibly from the middle as well. Also keep in mind that cellulose blinds like the ones in my apartment don't work so hot unless they are in their neutral position tilt-wise.

[krkeegan]

A yoyo is an interesting idea. I eventually found servo winches and winch drums that are used by rc truck enthusiasts, but they seem too small. I also found winches for rc sail boats, but again I think the drum is too small to hold the 4 feet of cord.

The cellular "shades" are like an accordion of paper, the do not let any light through unless they are opaque in nature and they have no tilt mechanism to rotate them like blinds do. I should have called them shades rather than blinds in my initial post. They are also apparently cellular no cellulose shades, go figure.

They really are very light weight. This is a decent photo of them: http://files.lutron.com/ImageLibrary/Pr ... e-1_hi.jpg

[bsagan]

Ooooo those types of shades. Lots depends on the thickness of the chord I guess. You could always just build your own drum out of wood as well.

Couple more things:
1) I assume there is a wire locking mechanism built into the shade housing. You will have to disable this if you want your mechanism to be able to lower the shades.
2) You will also need to figure out some sort of locking mechanism to hold the shades in the up position (and possibly down position as well so you don't put lateral force on your motor shaft). Your motor would obviously have the torque to keep it up (because it has the torque to raise it) but would be constantly consuming power which you probably don't want.

[krkeegan]

I have disabled the locking mechanism by rerouting the cord.

My plan is to use a worm gear to lock the shades in position.

[fll-freak]

ServoCity.com sells tons of stuff right up this alley.

[Mee_n_Mac]

I also found winches for rc sail boats, but again I think the drum is too small to hold the 4 feet of cord.

Why, other than for looks, must the drum hold all the cord ? Right now doesn't the shade work like a blind ... the cord is pulled down to make the shade go up ... and released to make the shade go down ? The pull cord is visible (doh) all the time. What if you used a windlass (or capstan) to motivate the cord up and down but left the cord hanging as it is ? Or perhaps stored in a box (like my boats anchor line is stored in a hold) ?

Note how the drum motivates the line but doesn't store it.

[unexpectedly]

ServoCity.com sells tons of stuff right up this alley.

I'm not sure if I love you or hate you for posting that link!

Thanks,
Chris

[fll-freak]

I would suggest that you love me. It would make my day.

[unexpectedly]

OK, I love you

[chartle]

ServoCity.com sells tons of stuff right up this alley.

I'm not sure if I love you or hate you for posting that link!

Thanks,
Chris

Yes I too hate that I know a Web site exists that has every mechanical part I have ever dreamed of needing during my 50 years or so years of life. I now no longer need to walk the rows of home Depot looking for some electrical or plumbing part for whatever widget I'm making.