Tuesday, June 26, 2018

[v2.0] Ok Google, Open my curtains!

This post is a follow-up to my previous post http://vignesh.foamsnet.com/2018/06/ok-google-open-my-curtains.html.

Note: I've created a github repository which contains the code and some more details. I intend to keep that up to date with newer ideas, etc. https://github.com/vickyg3/curtain-automation

When i posted the previous set-up on reddit, one of them suggested a better way to do this that will overcome the cons of the previous method (noise and lack of manual control).

In a nutshell, these are the replacements i made:
  • Use a stepper motor instead of a servo.
  • Use a timing belt pulley and timing belts instead of a pulley and rope.

Here are the updated list of parts (with links to the cheapest ones i could find online to keep the cost minimum - although i didn't necessarily buy it from these links):

* Mounting bracket for the pulley on the non-motor end - I used a servo mounting bracket with a long screw. I am sure there are better alternatives for this one - $12.99
* Super glue - $4
* Vibration dampener for stepper motor (optional but highly recommended to keep the noise down) - $2.98
* 12V DC adapter - $8.99

Total Cost - $67.69 (some of it can probably be gotten for a cheaper price on ebay/gearbest/aliexpress).

Step 1 - Screw in the mounting bracket

This is quite straightforward. I drilled in a couple of drywall anchors and screwed in the mounting bracket to the wall.

Step 2 - Install the motor and the vibration dampener

Place the vibration dampener on the motor. Make sure that the non-threaded holes on the dampener are touching the motor and use two M3 screws to attach the motor and the dampener. Attach the pulley wheel to the motor's shaft using the screws on the side of the pulley.

Now the motor can be mounted on to the mounting bracket using 2 M3 screws which connect to the dampener's threaded holes.
Motor attached to the mounting bracket (shown without the vibration dampener).

Step 3 - Install the pulley mounting bracket on the other end

I drilled a drywall anchor on the other end and screwed the pulley mounting bracket in. I then used a long screw with a couple of plastic fillers to hold the other pulley roughly in the center.

Step 4 - Loop the timing belt around the pulleys

I had bought an open ended timing belt. I looped it around either pulleys and tightened them as much as i could by hand and cut off the rest of the belt leaving about an inch of overlap. I then used super glue on the extra inch of belt to stick to them together with as much tension as possible. You could also use a clamp like this with a screw to close the loop on the belt.

At this point, you should be able to move the belt manually by hand by pulling it gently in either direction. If so, there is enough tension on the belt to move the curtains.

Step 5 - Attach the curtains to the timing belt

Just as before, i placed the curtains in the completely closed state and attached each curtain to either side of the timing belt using a safety pin.

Here's a sketch from before about how the pulleys and the curtains move:

Step 6 - Program the microcontroller

I used the same NodeMCU ESP8266 controller as before. Here's the gist that contains the Arduino sketch: https://gist.github.com/vickyg3/623ca535b565ed43c8b617a6f7c7c06f (it is a crude version and has a lot of room for improvement, but i left it for another day).

Step 7 - Microcontroller and Motor Driver setup

Here's the wiring:
* DIR+ to D2
* PUL+ to D5
* ENA+ to D8
* DIR-, PUL- and ENA- to GND (can either be bundled together or connected separately to individual GND pins on the NodeMCU)
* A+, A-, B+ and B- need to be connected to the motor (refer to the motor's spec for the wiring colors for your motor).
* The switches on the driver need to be set to ON, ON, OFF, ON, ON, OFF (S3 and S6 should be off).

Connect the DC power supply to the driver. I cut the ends of an old DC adapter and identified the positive and negative wires using a multimeter.

I then glued the driver and the NodeMCU board to the wall behind the curtain using small command strips. Any double sided tape should work as they aren't that heavy.

Step 8 - Home Assistant Configuration

That is pretty much it. For more details on how you can control it from Google Home/Alexa, please see my previous post.

The noise level of the old servo based system was around 60 decibels (as measured by an app on my phone). The new system with vibration dampeners works at 30-35 decibels and is barely audible. Most of the noise is from the curtains actually moving on the rod.

Here's how it works (The video is noisy because the roomba was running when i recorded the clip):

Here's a video without much of external noise:

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