I created an alarm device that will determine the temperature of your coffee (or tea), show you the status if it’s still HOT, WARM, or COLD with LEDs (red, yellow, and blue respectively), trigger a warning alarm if it is getting cold and will buzz continuously when it eventually gets cold.
For some reason I can't embed some of the Instagram videos showing the working prototype. You can find them embedded on this post.
Step 1: What You Need
- An Arduino UNO
- Three (3) LEDs -- red, yellow, blue
- Three (3) 220 ohm resistors
- A piezo (buzzer)
- TMP36 (temperature sensor)
- Several wires
- A makeshift pressure plate (I will show how to design for one later)
Step 2: Breadboard View & Schematics
Step 3: The Pressure Plate
Here's the tricky part. Think about the things you have at home that you can use to build a plate that is stable. The plate acts as a simple switch: when there is weight placed on the plate, it will close the circuit. If no object is placed on the plate, it should keep the circuit open.
E.g. Ballpens w/ springs inside that are quite tangible. Put them on 4 corners between 2 coasters and attach wires at the center that should touch each other when the springs are tight. Add other materials as needed to ensure its stability.
If you have a 3D printer handy, the better. You can design a plate for this purpose.
Step 4: The Code
You can download the Arduino sketch below. For the explanation of each block of code, you can reference back to my post here. Feel free to change the base temperature as I based mine from my current room temperature. Take note that the TMP36 measures the ambient temperature or the air temperature. If your area is too cold it might affect the results. Feel free to adjust your prototype as to circumvent any possible roadblocks to get the correct results.
Step 5: Test Your Prototype
Just brew your hot coffee and place it on the device plate!
Feel free to let me know if you find points of improvement for this device and if you come up with a better design. Cheers!