While smoke detectors are made to last a full decade, it's important to make sure yours is functioning properly so your home ...

He used an old smoke detector for the build; a nice choice since it’s loud, and designed for long-term battery operation. It also has a button for testing if the detector is working.

By cleverly patching into the test button on an old smoke detector he created a circuit ... Anyway, it’s still an interesting reuse of these ubiquitous, and life-saving, devices.