<p>The development of self-powered environmental and chemical sensing systems capable of reliable operation under irregular mechanical inputs is essential for realizing practical and autonomous electronics. Here, we present a mechanically-triggered, self-powered triboelectric sensor platform that overcomes this limitation through arbitrary-to-constant mechanical input conversion. The platform employs a magnetic latching mechanism that stores elastic potential energy in a cantilever coupled with a flexible sagged film and releases it once an external displacement exceeds a predefined threshold. Once released, the cantilever exhibits a high-frequency free vibration at its natural frequency of approximately 52.6 Hz and a consistent amplitude of 8.2 mm initially, independent of the input amplitude range of 25–35 mm and frequency range of 0.1–1 Hz. This process produces stable electrical outputs through the triboelectric energy conversion mechanism with less than 9.6% deviation across the tested input conditions. To demonstrate the versatility of this platform, we fabricated two types of active sensors, a humidity sensor based on charge dissipation in a hydrolyzed electrospun polyethylene terephthalate layer and an ammonia sensor utilizing impedance modulation of a polyaniline layer. Both devices exhibited highly stable, mechanical input-independent performance, confirming the platform’s adaptability to different sensing mechanisms and materials. This mechanically triggered architecture provides a robust structural solution to an often overlooked source of signal ambiguity in self-powered sensors, offering the potential for reliable, portable, and human-interactive sensing applications.</p><p></p>