How to build a microcontroller-driven cold brew coffee drip tower

Our friend and frequent Boing Boing contributor John Edgar Park built a large cold brew coffee drip tower using laser cut parts, lab glassware, a food-safe solenoid valve, and Arduino-based controller. I'm waiting for him to invite me over for a glass of ice coffee!

I love cold brew coffee. Its rich and delicious flavor, and low acidity, means it tastes great over ice. Traditional hot-brewed coffee methods simply can't compare; when chilled and served on ice they tend to taste diluted and acidic. I have a small commercial drip tower that works very well, however, given the fact that cold brew takes up to 18 hours to brew, it's disappointing to finish it off in just a few drinks. You can buy large cold-brew towers, but they're very expensive, aimed at coffee shops. I decided to build a much larger brewing tower from scratch, and to make it considerably higher precision while I was at it - drip rate is everything when it comes to cold brew - using a microcontroller-driven solenoid valve for exact drip rate.