Beta fish are one of the easiest pets to care for. So when [Derek] gave his girlfriend one for Valentine’s day he thought the job was done. Turns out these tropical pets want 75-80 F water and that’s not going to happen in a plain old bowl when you keep your home thermostat in the mid sixties during the winter. While looking for a simple heating solution he stumbled across the idea of using a cheap drip coffee maker as an aquarium.
The two main components are already in place: a clear glass vessel for the water and a way to heat it. The real trick is to use the heating element to gently warm the water to the appropriate temperature. Perhaps the key piece of the project is that the device already had a timer that shut off the heating element. This translates to easy control with his MSP430 microcontroller as it means there’s a relay present. He also patched into the two seven-segment displays to give him feedback on the temperature currently being read by the RL1003 thermistor which is submerged in the water. You’ll also note that he added a few LEDs to the lid to give the aquarium some inner glow.