I want to block harsh reflected sunlight in the early mornings, but I also want daylight to enter my room later in day.
This device automatically closes window blinds before sunrise, then opens the window blinds at a time specified by the user.
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The opaque white rectangles which block light when they are parallel to the window are called slats.
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To rotate the slats by hand, you rotate a stick called a wand.
A motor rotates the wand to open & close the blinds. An accelerometer taped to one of the slats provides feedback. A Raspberry Pi keeps track of time, controls the motor, and monitors the accelerometer. The time is displayed on a ring of addressable RGB LEDs.
graph LR;
rpi[Raspberry Pi<br>v3 Model B] --- MotorDriver[Motor driver<br>L298N module] --- motor[DC gearmotor] --- WindowBlindsWand[Window blinds wand];
rpi --- Accelerometer[Accelerometer<br>MPU-6050]
rpi --- clock[Addressable RGB LED clock];
The accelerometer module also contains a gyroscope, which is not used in this project.
There are three power supplies: 5V for the Raspberry Pi, another 5V with more current for the addressable RGB LEDs, and 24V for the motor.
A little prototype board with a bunch of screw terminals helps manage wiring. It also houses a capacitor and resistor as recommended in the Adafruit NeoPixel Überguide.
For this project I purchased a DuPont crimp tool AND a ferrule crimp tool. Both are a joy to use and made the wiring much nicer.
The motor is made by Source Engineering Inc and has this ridiculously long model number:
37JB270G/32ZYT30-2468
I got it at HSC Electronics (rest in peace) in 2018. Here's a picture of the label, which lists some slightly interesting specs:
The motor has a bolt hole circle which is 31 (thirty-one) millimeters in diameter.
Surely that's a mistake and it's actually 30 (thirty) mm... no, it really is 31 (thirty-one) mm.
Amazingly, 31mm is normal for this size of gearmotor. The key is that the outside diameter of the gearbox is 37 (thirty-seven) millimeters.
Searching for "31mm gearmotor mount" returns a scattering of suitable mounting plates. Searching for "37mm gearmotor mount" instead returns tons of results for what we want.
I had such a hard time figuring this out that I am stealing pictures from the internet, editing them, and re-hosting them in this Git repository:
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The holes have M3 threads. There are usually five or six of them.
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A Simpson Strong-Tie A44 angle bracket is the perfect size to support the motor mounting plate.
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Two adorable one-inch C-clamps hold the angle bracket onto the windowsill.
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Some M3 machine screws & nuts hold all the metal parts together.
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A 1/4-inch diameter wooden dowel replaces the original window blinds wand.
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A piece of 1/4-inch inside diameter vinyl tube zip-tied to the motor shaft and dowel acts as a torque-limiting flexible shaft coupler.
I want to see what time the Raspberry Pi thinks it it, and when it will open/close the blinds, without leaving a computer monitor on.
I'm using a generic WS2812B addressable LED (Neopixel) ring, 35 LEDs, 96mm outside diameter.
A logic level shifter is theoretically needed because the Raspberry Pi GPIO is 3.3V but the addressable LEDs operate on 5V. For some reason, my setup has always worked fine without a logic level shifter.
Here is a prototype I used to work out the logic: https://editor.p5js.org/pfroud/sketches/SYHjqIggA
Screenshot of low-quality GUI:
