An automated crank window opening system (Work in progress) built with off-the-shelf components and custom 3D printed mounting brackets, integrated with Home Assistant, an open source home automation framework.
Despite month of research, I can't seem find an affordable commercial solution that works with most awning or casement windows sold in the U.S. Plus, I really, really don't want to bother our AI overlord hundreds or even thousands mile away, just to open our windows.
So I started looking for DIY solutions. This project is based on the solution described in DrZzs' YouTube video with two major changes. First, I use a current sensor to stop the motor, thus providing safety stop to prevent injury by closing windows. Second, I tried to build a bracket mounting on the window itself, instead of on the window sill.
This is very much a work in progress. As a software engineer, I have ZERO experience in embedded system or mechanical system. And my parts are damn ugly now. I put this project on open source platform, hoping to get suggestions for improvement.
Here is a list of the window opener's system and components that I found online.
Either a chain actuator or a pair of linear actuators. This is probably the most common and affordable solutions online. There are quite a few manufactures offering this product, price ranging from $180 to $600 a piece. They sell either the actuator only, or some include remote control system with their own app. I found this solution is not very bug screen friendly.
Marvin offers fully integrated automated windows. This solution looks really nice. Expensive too. Looks like we have to bother our AI overlord for such a chore.
Truth Crank Window Opener seems to be the solution I needed, except for its steep price, and proprietary control system.
They also sell the motor only at a lower price. Still pretty expense.
The goal is to develop a solution with the following features
- Affordable
- Automated window operation locally, without relying on internet.
- Easy installation, and compatible with most awning window with bug screens sold in the U.S.
- Safety stop.
The system is composed of two parts, electronic controls and mechanical parts.
The idea is to use an electric motor to turn the crank of the manual opener. So we need a motor, mounting bracket to hold the motor in place, and a coupler that connect the motor shaft to the crank axle.
We use a 12V DC Motor, with rated torque 8kg.cm. This motor has a D shaped output shaft. And the window's crank opener has a splined axle. To connect them, I designed a coupler on OnShape.com and produced the plastic part using a 3d printer.
The mounting bracket has two parts. The first part clips onto the window crank hardware base.
The motor, with the coupler connected, is fastened onto the second part, that are later connected to the first part.
The connected bracket is shown in the picture above, bulky and ugly, partly due to my inferior 3D design skills, partly due to the awkward connection from the motor's D shaft to the splined axle of the window hardware.
This is not tested. One potential alternative, is to use a Truth Sentry II motor instead. It has the output socket that grabs the splined axle. This allows the motor to sit close to the crank hardware, reducing bulk. A downside is its price, nearly $600 per motor.
The control system is composed of a L298N motor controller, an INA219 current sensor, and a D1 Mini. And the wiring diagram:
The D1 Mini is the brain that execute the control logic, it reads motor current with INA219, and spinning the motor with L298N. We use ESPHome as a Home Assistant add on to program this.
When a DC motor is running, its current rises when it has to exert more forces. The plan is to use this to detect motor stalling, either due to a hand got caught in the closing window, or the window is fully closed. The motor should be turned off either way.
ESPHome hides a lot of complexity, allow easy configuration using yaml file. At this point, cranky_conf.yaml file contains all the necessary programming. Quite a bit of embedded C code is used to handle the complexity that came with motor current sensing and controls.
We could simply set a max current threshold, that when exceeded, just turn off the motor. Unfortunately, this does not work, since the current is usually high for a short amount of time when the motor starts. This short period of high current is called inrush current. Also, after the window is fully closed, we want to reverse the motor just a little bit to release the pressure exerted on the plastic shaft coupler. A complex piece of embedded C code is used to deal with these complexities.