To servo or not to servo - the grand finale!
And the shade motor is finally complete.
After addressing the existential conundrum of whether to actuate the window shade drive with a boring servo motor/disconnect coupling arrangement or go through the thrill and excitement of developing a new bi-directional overrunning clutch, I reluctantly went with the servo/coupling concept, and the shade motor is now complete.
While a very simple concept, this was a fun project, with plenty of setbacks and learning.
The most important takeaway is that I suck at soldering: I used a standard prototype board and soldered jumpers for the connections, resulting in a circuit board that, while perfectly functional, could very well be one of the contraptions built by The Little Rascals.
My next step, therefore, is to learn KiCAD so I can design and order decent printed circuit boards for my next mechatronics projects.
The shade itself came in with a defect, and after a few dozen phone calls, e-mails and chat in their website, the manufacturer sent me a replacement ... with two defects. Maybe due to COVID they didn’t want the first one back when they sent me the replacement, so I just fixed both myself and now I have 2 shades. It’s just as well, since I have 2 windows to cover anyway!
Now, instead of a voice activated remote control that only works when I’m around (“Honey, please go and tape a sheet of paper to the window, the sun is blinding me”), my wife has a motorized shade controlled by an infra-red remote.
In order to minimize clutter at her workstation I used the same remote that she’s already using for the space heater. Since it’s infra-red and the heater and shade are at opposite ends of the room it works just fine.
The design parameters were met and are as follows:
Smaller than 230 x 150 x 150 mm which is the largest envelope for my 3D printers.
Actuated by a low voltage DC motor.
Moves while the remote’s buttons are being pressed, stops when the buttons are released.
The shade can be moved manually without back driving the motor.
When the shade reaches the top or bottom limit of travel the motor automatically stops, a blue LED flashes and a buzzer beeps 3 times.
No need to reset the end of travel sensors after moving the shade manually or after power failures.
Maintenance free.
Low cost (who would have guessed?).
As Tom Sawyer found out when getting the other kids to whitewash Aunt Polly’s fence, doing something that can otherwise be a predicament turns out to be a lot of fun when you do it because you want to!
And here are the pre-installation test and of the final result.