[chbot] Home Automation - Curtains

[Helmut Walle]

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 
> <mailto: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/
>     <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 <mailto: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-connection-zip-ties.jpg
>         <http://diyprojects.eu/wp-content/uploads/2017/01/belt-connection-zip-ties.jpg>
>
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