The point of this project was to automate the window blinds in my apartment. They're genuinely quite a hassle. I have fourteen-foot ceilings and ten-foot-tall windows. Raising the blinds is easy enough, just pull down ten feet of cord. But lowering them is much more annoying since I have the traditional aluminum blinds that latch in place with a pawl mechanism so I have to pull the cord at an angle to un-latch them and lower them. With a ten foot height, that means I have to carry the cord to the other side of the room and climb around or over furniture to maintain the proper angle. And my apartment is at the front of my building at street level so I like having the blinds closed before sunset but I'm not always at home at the right time to do it. And I really need to open my blinds every single day because my apartment is a tomb with the blinds closed. So it genuinely made sense to automate the window blinds. And besides, I hadn't designed or built an actuator in quite a few years and it sounded fun.
I started out building a novel actuator from scratch. I managed to incorporate some clever details like roller nuts and v1 was extremely compact and simple. I was pretty proud of that design. Unfortunately it sounded like I was running a blender for several minutes every morning and evening. It wasn't very pleasant to actually be in the room while the blinds were moving. And so began the long and slow process of multiple iterations of redesign. I kept making the smallest possible changes. Upgrading from brushed DC motors to brushless. Upgrading from spur gears to worm gears. Upgrading from plastic screws to metal screws. So many small changes. All to save a few dollars per window. And in doing so I spent an absurd amount of time on the project. Far too much time. I should have just jumped straight to the guaranteed solution I knew from day one because that's where I ended up.
Here I am, at version 5 of this actuator. Version 5 that I actually built. I designed several other revisions that never made it to production. And version 5.4 of my electrical system. And who knows what version of code. The whole point of all of this redesign was to minimize noise. And like I said, I ended up going with the solution that I knew would be best on day one. I've built a very simple actuator that uses BLDC motors wound for low-speed/high-torque, harmonic drives for compact silent gear reduction, and FOC control for ultra-smooth and silent motion. Textbook. That's basically as quiet as you can get short of direct drive (which has plenty of its own problems). And it did cost more. These v5 actuators cost about $100/each, compared to $20/each for v1. But how much time would it have saved me to just go with this from the beginning? More than $480 worth, I can promise you.
But v5 works great. Not completely silent, but pretty darn close. The only noise comes from the harmonic drives spinning at ~20Hz, and that's not too bad. It's about as loud as the noise of the blinds themselves moving up and down. And they're much faster than v4, which had to be speed-limited due to the amount of noise the planetary spur gears and motor drivers generated. v3 was actually pretty okay, faster and quieter than v4, but still not as fast or quiet as I wanted. v5 is good. I have no complaints. I'm ending this project here.