Tuesday, August 6, 2019

Home Automation - Sun blinders, plans vs reality

Outdoor lighting prevention, part 1

As you may have deduced from my previous post, living in Sweden in autumn/spring, you will notice that the sun doesn't go up very high unless it's high summer. It shines, more or less horisontally, right through your windows and onto your TV, computer monitor or face. That quickly gets annoying, plus the houses are built for winter, not summer, so when it's +30 degrees Celcius outside and sunny, it gets awfully hot inside.

Thus, some external sun blinders are nice, as they keep heat and solar megalumens outside (where it belongs during summer). They still allow you to see your more-or-less-green lawn and the state of the great outside. Hence, I prefer them quite a bit before curtains in various forms. Also, our house had them when we bought it.

The idea for this project started after we built a new patio-roof starting at the house wall . We had to replace the 8-foot manual crank pole to the 2nd floor blinder as the roof physically blocked it. So, I bought and installed an electric motor instead. Quite nice, but it added 3000 SEK (~300€) to the roof project cost. Ugh, However, the motor is actually quite neat, AC-mains driven (one wire for up, another for down, plus neutral and earth) and adjustable end-stops to avoid damaging anything, plus it fits inside the tube.

I declined the wireless option (didn't even ask for price) as I didn't feel it was worth it then (I didn't want to buy the motor in the first place!). My experience was that such systems are usually proprietary, closed, expensive ones that are hard to integrate with much anything else.

Then, as we spent the rest of that summer moving the blinder up and down more or less every day, down in the morning sun (which comes up at about 5.a.m, before any wholesome beings are awake),
 up in wind and rain, or after 2 p.m. when the sun wasn't shining in anymore and you actually wanted to enjoy the view, my inner nerd/optimizer finally had it. We had to automate this!

This was a year or so before I got the Raspberry/Tellstick/Nexa combo, so this was actually my first home automation project.

Anyway, I bought a bunch of Arduinos but nothing really came from that. Instead, I got a Nexa motor receiver and a wall transmitter. The transmitter is used to lower the blinds in the morning (when one wakes up) and the Raspberry/Tellstick then sends a signal (essentially "lamp off") to retract the blinders at 14:00 every day. This has worked well enough, although I would like for it to automatically lower in the early morning (04-05:00) during summer. I'm not there yet.

However, I am now building a controller for a second sun cover (5x4m on top of our transparent patio roof), and that is almost done. Stand by for more info. :) 

First adventures in Adobe Fusion 360

I made a thing!


This is a split timing belt pulley that will drive the sun-cover on my terrace. It is is currently manually operated and quite often fails to retract when the sun goes down, it starts to rain or the tenants leave for vacation.

The base is a 32 tooth T5 belt pulley from MacMaster-Carr. (I had a T5 belt and some smaller pulleys already.)

The sides are extended on to accommodate for clamping/fastening.
The belt guides where made a bit thicker and a fillet was added make the sides a bit more robust.
Additionally, the gap between the two halves have been reduced by 0.5 mm to actually provide some clamping force.

Four M5 bolts/nuts pairs clamp on the 13mm axle.

Two M6 set screws to grip into the axle itself. (Those holes will be threaded manually. If the plastic isn't strong enough I can always drill it up a bit larger and insert helicoils, or redesign with nut cutouts on the inside similar to the outside).

The plan is to 3D-print it, which will look something like this:


I'm quite happy with this little piece, and that I managed to do it without any previous Fusion 360 experience in a few hours. :-D

The step file is available for download: 13x5T-32-Split v21.step