Solder fume fan

Created a GitHub repo for the files, recreating some of the steps on the way to the current 3D model. Removed the model file in favor of a link to the GitHub repo where I intend to keep working, soon adding some software and electronics info. 

Fleshed out my 3D model to include a housing for the fan with screw holes for mounting and a filter holder in front of the fan, with a separating "X" between the two. Also added a hole for the fan cable to exit the fan holder. I plan to mount the controller on the outside of the fan holder, on the top.

I've started out very simple to get going, since I do need a solder fume extraction fan right now, but also to test out some of the things in my comfort zone, putting a bit of throw-away software together to get things rolling. My current hack uses a basic Arduino skeleton, poking directly into the avr registers to get the target pwm frequency of 25kHz. It mostly works but falls down at very low/high duty cycles, since in the current pwm mode I need to update the threshold value in the interrupt handler at each counter overflow. But that's OK since I'm just testing things out. I'm currently running the fan directly off of 12V from a lab supply and the arduino from USB.

I also had some fun with a serial based UI where you can control the pwm speed with the arrow keys and get a nice volume meter style gauge to show you the current duty cycle setting.

Right now I've started experimenting with openscad to make a simple, printable design to replace the cardboard and tape prototype.