windmill

a relatively simple and extremely cheap ArtNet / OSC / sACN receiver that powers a twelve foot prop windmill

This project pulls together OpenLightingArchitecture and the OrangePi fork of the wiringPi project to create a $40 ArtNet / OSC / sACN receiver. In the real world, it is networked into an ArtNet universe, and exposes two channels: one to control the speed of the DC motor powering the windmill, and another to control the direction (used as a binary switch). It will debut (fingers crossed) in a production of The Wizard of Oz, which is where the silly useless print statements come from.

I have an obsession stuffing Rust everywhere under the sun, mostly for the fun and challenge. To do so, this project makes pretty good use of cxx to create easy ffi bindings into C++ and C libraries. I hope this project inspires you and makes it quick and easy to build your own custom DMX fixtures.

Requirements

• An Orange Pi. Honestly you can probably use whatever SBC you have floating around, as long as it has the GPIO to do what you want. If you want to build an actual windmill or drive a motor, you'll want something that can drive an actual pwm signal in hardware.
• Everything else is optional, but you'll likely want to have on hand some relay drivers and other fun components to make your controller do something.
• Some base OS for your OrangePi. I used Armbian, which was new for me as an Arch user. It worked great, but I don't think there's anything too OS-specific here.

Usage

This project makes a lot of assumptions in order to be compliant with the licensing requirements of both OpenLightingArchitecture and WiringPi.

1. Compile and install shared libraries for wiringPi and ola. This is going to be hardware specific a lot of the time unless you're trying to copy my project exactly (in which case, buy an OrangePi 3 LTS).
2. Configure your SBC to enable the PWM overlay if it isn't by default. e.g. for Armbian:

   # /boot/armbianEnv.txt
   overlays=pwm

3. Ensure olad is running, either via systemd or however you love to manage daemon processes.
4. Patch your ola interfaces via ola_patch.
5. cargo build [--release] to compile this program. Unfortunately, with this being a hardware project, this will only compile on the actual hardware, or on hardware that can also compile wiringPi. ola is easy to get compiled in a whole bunch of places.
6. Run the program sudo ./target/[debug|release]/windmill. root access is required for wiringPi. I assume you're not going to network this into critical infrastructure or connect it to the open internet (that'd be dumb). If you want to do that, find a rootless way to interface with your GPIO pins.
7. If nothing bows up, you should have a functional DMX windmill!
8. There's a simple systemd unit file in here as well that you can install that will start windmill automatically when the OrangePi starts. That should make it effectively headless!

Things I Wish I Knew

• For whatever reason, the hardware PWM, at least as of writing with whatever version of wiringOP I built against defaulted the PWM control to "inverted", which is active-low. That means the default duty_cycle of 0 actually runs a solid high signal, which when directly mounted to your motor controller likes to make things go VERY FAST and VERY immediately. This is something that is probably totally fixable, but the quickest path to success for my goal of a headless windmill was to route the PWM signal through a spare relay I had on the normally-open channel, and have the application trigger that relay when it was initialized (if you read the code, you'll see). It works, and means I don't need to do any jank plugging / switching in the theatre.

Reach Out!

If you find this useful or interesting, drop me a line. I really loved this project and love the idea of making the arts more accessible to the world.