CLIMATE ALARM
EMBEDDED SYSTEMS, FABRICATION, ELECTRICAL WIRING
2026
INTRODUCTION
I built a room temperature monitor: an Arduino-based device that reads ambient temperature every 500 milliseconds, displays both Celsius and Fahrenheit live on an I2C LCD, and triggers an alarm if the reading falls outside a set temperature range (80–90°F for the demo). Everything was soldered, packed into an ABS enclosure, powered by a 9V battery with a switch, and color-coded by wire function. The alarm itself had a visual component (blinking red LED) and an audio one (piezo buzzer), with a green LED staying on any time the device was powered.
DESIGN & BUILD
I modeled the full ABS enclosure in Onshape, 3D printed it, then used a drill press to bore out the holes for the LEDs, switch, and any other exterior components
The alarm logic required millis()-based timers rather than delay() — the LED flash interval and song note duration each needed their own non-blocking timer so both could run at the same time without stalling the temperature read loop Switch wires got spade connectors crimped on instead of soldered so I could disconnect them, thread the wires through the enclosure wall, and reconnect
FINAL PERFORMANCE
The device functions correctly with temperature updates twice per second, both units displaying simultaneously, and a looping Happy Birthday melody with a flashing red LED that triggers the moment the reading goes outside 80–90°F and cuts off immediately when it comes back in range The two things I'd change in the next version: first, the alert range is hardcoded (80–90°F is just the demo threshold), so adjusting it means plugging in a laptop and reflashing. Physical buttons would make it actually usable as a standalone device. Second, 14 hours of battery life is fine for a demo but not for permanent room monitoring. A wall adapter would fix that, but the battery was a simple and cheap power source, so it was the right call for this project
