This device lets you know how long your office’s coffee has been sitting out

Don’t know how old that coffee is? BrewDoo does.

In the morning, the coffee tends to go pretty fast throughout the office. However, as the day goes on, caffeine consumption often dwindles down a bit. And when it’s time for that late afternoon pick-me-up, it’s sometimes difficult to guess just how long the coffee has been sitting in the pot. Luckily, Maker Paul Kerchen has devised a solution to keep track of that.


“I had two design constraints: no modifications to the brewing system were allowed and the device had to be simple to use. The company I work for leases their brewing equipment from a coffee supply company, so even permanently fixing anything to the brewing unit or carafes was out of the question, let alone hacking into the wiring or mechanical parts of the system. This meant that making it as simple as possible to use was imperative, because it would have to rely on the coffee drinkers of the office to be diligent about telling the device whenever a pot was brewed,” Kerchen writes.

How the BrewDoo works is pretty straightforward: After fresh coffee is brewed, a timer tasked with tracking each respective pot (in Kerchen’s case, his office has two carafes) is triggered by pressing a button to reset the brew timer. Once reset, an RGB LED will immediately display green, and over the course of an hour, will gradually transition to yellow and eventually red — meaning “don’t drink!”


Meanwhile, an LCD display reveals the time that has lapsed since each timer was reset. What this does is takes the guesswork out and provides a user and their colleagues an at-a-glance indication of the coffee’s age. In the event that a pot’s timer hasn’t been reset in four or more hours, the device will turn off the LED for that pot and show a question mark on its screen. This is basically BrewDoo’s way of saying, “I don’t know… you’re on your own!”

Though BrewDoo was prototyped using an Arduino Uno, his final version was built around an ATmega328 based custom board. Since the Maker’s company leases their coffee equipment, he decided to fabricate an enclosure that was cut with his CNC machine using g-code that he wrote from scratch. The casing is attached to the machine via a pair of hard-drive magnets and powered by an old Motorola cellphone charger.


Want a BrewDoo for yourself? Head over to the project’s official page here.

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