Cold Coffee Alarm Device Using Arduino Uno

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 the prototype videos, you can watch them on my blog post: Creating A Cold Coffee Alarm Device using Arduino

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.