DIY Smart Coaster Tells You When Coffee Is Safe to Drink
This electronic coaster designed by gokux is a cool solution to cold coffee.
There is nothing worse than room-temperature coffee and, no, it isn’t anything like cold brew. The obvious solution is to chug your coffee before it has a chance to ruin your morning, but then you end up burning your mouth. To prevent injury, you let your coffee sit for a little while to cool down. But, inevitably, you forget about it until its cold and unpalatable. There has got to be a better way! There is, thanks to this DIY smart coaster designed by gokux.
This electronic coaster doesn’t do anything to keep the mug warm (though that would be a nice feature). Instead, it simply monitors the mug’s temperature and tells the user when it is within a range ideal for consumption. A little display on the front of the coaster shows the current temperature and an indicator. A caution symbol means that it is still too hot, a snowflake means that it is too cold, and a thumbs-up means that it is just right. The sweet spot is 50°C-70°C (about 122°F to 158°F), but anyone who builds this coaster can change the thresholds in the code if they prefer different temperatures.
The key component here is a contactless infrared thermometer (a GY906 MLX90614ESF-BAA module) that points at the base of the mug. A Seeed Studio XIAO SAMD21 development board monitors that thermometer and shows the results on a small 0.91” 128×32 OLED screen. Power comes from a USB-C cable.
Most of the coaster’s attractive enclosure is 3D-printable. But the heat from the mug would damage typical 3D printing materials. For that reason, gokux designed this with an aluminum surface on which the mug rests. That should act as a radiator and dissipate most of the heat before it reaches the plastic. As a bonus, it may even help cool down the mug’s contents a bit faster! The aluminum plate can be cut from sheet by laser, plasma, water jet, or CNC, which should make it relatively affordable to order from a fabrication service if you don’t have the tools to make it yourself.
The only disadvantage of this design is that it isn’t monitoring the temperature of the beverage — it is just checking the temperature of the vessel’s outer surface. So it won’t be very useful for a thermos that is well-insulated.