SW-420 NC-Type Vibration Sensor Module with Alarm Switch

A simple digital switch triggered by shock or movement

The SW-420 module uses a normally-closed (NC) vibration sensor, meaning its internal contact stays closed under normal, still conditions and momentarily opens when it experiences vibration or shock. When inactive, the module's output stays low with its indicator LED off; when vibration causes the switch to briefly disconnect, the output goes high, giving a clean digital trigger event that a microcontroller can watch for.

That comparator-based output, described as clean, well-shaped and with strong driving ability at up to 15mA, comes from an onboard wide-voltage LM393 comparator chip, which converts the raw switch behaviour into a stable digital high or low signal rather than a noisy raw contact bounce.

Setup and applications

Operating voltage runs from 3.3V to 5V, so it connects directly to both 3.3V and 5V microcontroller platforms without extra interfacing, and output format is a straightforward digital switching signal (0 and 1). Screw holes are provided on the board for secure, permanent mounting, which matters for a sensor meant to detect physical shock or vibration reliably rather than shift out of position.

Listed applications span various oscillation-triggered projects, general Arduino experiments, earthquake alarm systems, motorcycle alarms, and anti-theft alarms, all cases where a simple, robust vibration-triggered digital signal is exactly what's needed rather than a detailed measurement of vibration intensity.

Who it suits

Anyone building a basic shock or tamper alarm, a simple earthquake or impact detector, or a vibration-triggered project that just needs a reliable digital on/off signal rather than detailed vibration data will find the SW-420 a straightforward, well-suited component.

Questions buyers ask

How does the sensor detect vibration?

Its normally-closed contact briefly opens during vibration, which the onboard comparator turns into a clean digital signal.

What voltage does it run on?

3.3V to 5V.

What chip generates the digital output?

An LM393 comparator.