[chbot] Home Automation - Curtains

[Charles Manning]

Run the cord through rosin

That helps it grip.

Have you considered that cord with little beads on it? See
http://www.goelst.com/uploads/images/Gallery/7400-7800/7800.jpg tht will
engage and drive even if it is not tight.



On Mon, Sep 25, 2017 at 6:04 PM, Andrew Errington <erringtona at gmail.com>
wrote:

> Thanks Helmut.
>
> I can't attach the cord to the pulley as it is a continuous loop from one
> side of the window to the other.  So it must be free to wind "on" on one
> side and "off" on the other.
>
> I have made several turns around the drive pulley, but sometimes the
> incoming cord winds on top of the other coils instead of next to them, so
> it snarls up.  I think I need fatter cord and fewer turns to avoid this.
>
> I need grippy, stretch-free cord, and grippy pulleys with only one turn
> around them.  A spring would work for tension, or a rubber band cut from a
> bicycle inner tube.  I might try that too.
>
> Thanks,
>
> Andrew
>
>
> On Sep 25, 2017 5:44 PM, "Helmut Walle" <helmut.walle at gmail.com> wrote:
>
> There are two ways to get traction: rather than just winding it around the
> drive pulley, clamp or attach it to a point on the circumference there, so
> that it must follow when the wheels are turning... Or wind it around the
> drive pulley a number of times - "rope" friction around a pulley is
> proportional to the number of turns, everything else being equal. Also, for
> keeping it taut, you can use a steel spring; this is quite common in
> string-based transmissions.
>
> On 25/09/17 17:38, Andrew Errington wrote:
>
> There's also "fishing line I happen to have to hand", which is clearly
> unsuitable in this case.
>
> I'm going to try the builder's line again.  This time with a cable tie
> that I can crank down on to get the tension.
>
> Thanks,
>
> Andrew
>
>
> On Sep 25, 2017 5:01 PM, "Charles Manning" <cdhmanning at gmail.com> wrote:
>
> There's fishing line... and fishing line.
>
> Nylon stretches like anything. Braid (eg. https://www.completeangler.co.
> nz/line-95/braid-97/) has practically no stretch and is available in many
> colours and strengths.
>
>
> On Mon, Sep 25, 2017 at 3:51 PM, Andrew Errington <erringtona at gmail.com>
> wrote:
>
>> Hi everyone,
>>
>> I thought I'd start a new thread, as we got away from the relative merits
>> of Banggood vs DealExtreme.
>>
>> I am trying to motorise my curtains, particularly as there are six
>> windows in one room, plus home automation is cool.
>>
>> So far I have identified a suitable motor and gearbox, 12Vdc supply,
>> 60rpm output, with good torque and fairly quiet.
>>
>> At one end the motor, with a 16-tooth GT2 pulley, is attached to the wall
>> using a purlin bracket (purlin brackets are cool).  At the other, I am
>> using a sewing-machine bobbin on an M6 bolt as a pulley.
>>
>> It's early days, but I have tried builder's line, which doesn't stretch,
>> but does slip.  I have tried fishing line, which does stretch, and slips.
>>
>> I think GT2 toothed belt would work well, but I haven't tried it yet.
>>
>> The motor is temporarily connected to a 12V battery for testing.  Later I
>> will use an ESP8266 with microPython to control the motor.
>>
>> Finally, I'll link it to home automation software and relax in my chair
>> as the sun goes down and the curtains gently and quietly close.
>>
>> That's my plan, but there is plenty of room for alternatives or failure.
>>
>> The attached link is for a belt clamp and tensioner made from zip-ties,
>> which I think I will adopt!
>>
>> Best wishes,
>>
>> Andrew
>>
>> http://diyprojects.eu/wp-content/uploads/2017/01/belt-connec
>> tion-zip-ties.jpg
>>
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