Zigbee Vibration Monitor, a ESP32 project

This project turns an ESP32 microcontroller and SW-420 vibration sensor into a networked monitor that detects and reports vibration events over Wi-Fi. The sensor module outputs a digital signal when vibration is detected, which the ESP32 processes with debouncing and event counting to filter out noise and false triggers.

Builders will receive a complete wiring diagram showing how to connect the sensor to the ESP32, a full parts list, Arduino firmware with Wi-Fi connectivity and a local web interface, and step-by-step assembly instructions. The guide includes configuration details for adjusting sensor sensitivity and understanding the JSON status endpoint that reports real-time vibration state and event counts.

Wiring diagram

Gather all the parts

Qty	Component
1	SW-420 Vibration Sensor Module SW-420 adjustable vibration module Non-directional vibration detection module based on the SW-420 vibration switch and LM393 voltage comparator. Outputs a digital HIGH/LOW signal on the DO pin when vibration or movement is detected. Sensitivity is adjustable via an on-board 10 kΩ potentiometer. Operates at 3.3 V or 5 V, making it fully compatible with the Raspberry Pi Pico's 3.3 V logic. No external library is required — standard digitalRead() calls are sufficient.

Qty

Component

SW-420 Vibration Sensor Module

SW-420 adjustable vibration module

Non-directional vibration detection module based on the SW-420 vibration switch and LM393 voltage comparator. Outputs a digital HIGH/LOW signal on the DO pin when vibration or movement is detected. Sensitivity is adjustable via an on-board 10 kΩ potentiometer. Operates at 3.3 V or 5 V, making it fully compatible with the Raspberry Pi Pico's 3.3 V logic. No external library is required — standard digitalRead() calls are sufficient.

Assemble it in 4 steps

1. Place the board and sensor

Put the ESP32 DevKit v1 and the SW-420 vibration module on a breadboard or non-metal surface. Keep the SW-420 on, or firmly connected to, the object whose shaking you want to notice.

The small blue adjustment screw on the SW-420 changes how easily it reacts. Start with it near the middle.
Do not let loose wires touch the underside of the ESP32 board or the metal sensor can; a short circuit can damage the board.

2. Connect the power wires

Use a red jumper wire from the ESP32 pin marked 3V3 to the SW-420 pin marked VCC (power). Use a black jumper wire from an ESP32 pin marked GND to the SW-420 pin marked GND (ground).

Use the ESP32 pin marked 3V3, not 5V. This keeps the sensor's output safe for the ESP32 input.
Make sure VCC and GND are not swapped — swapped power can damage the sensor module.

3. Connect the vibration signal wire

Use a third jumper wire from the SW-420 pin marked DO to ESP32 GPIO27 (signal). On many ESP32 DevKit v1 boards the pin is printed as 27 along the header; follow the printed GPIO number.

Follow the SW-420's printed pin labels VCC, GND, and DO rather than relying on their physical order.
Do not connect the SW-420 DO wire to the ESP32 5V pin; it must go only to GPIO27.

4. Adjust the sensor

Plug the ESP32 into your computer with USB. Gently tap or shake the object holding the SW-420, then turn the small blue adjustment screw a tiny amount at a time until normal background movement does not trigger it but the movement you care about does.

The small indicator light on most SW-420 modules changes when the module detects movement.
Do not force the small adjustment screw past its stops; forcing it can break the adjustment part.

Review all connections

1. Connections between "sw420_1" and "ESP32"

Function	sw420_1	ESP32
`power`	VCC	3V3
`ground`	GND	GND
`digital`	DO	GPIO 27

Deploy the firmware

main.cppOpen in Schematik

#include <Arduino.h>
#include <WiFi.h>
#include <WebServer.h>

// Local Wi-Fi credentials supplied for this sensor.

// Forward declarations
void handleStatus();
void handleRoot();
void connectWiFi();

const char *WIFI_SSID = "Home2";
const char *WIFI_PASSWORD = "HomeSweetHome2";

constexpr uint8_t VIBRATION_PIN = 27;
constexpr uint32_t DEBOUNCE_MS = 80;
constexpr uint32_t EVENT_HOLD_MS = 2000;
constexpr uint32_t RETRIGGER_LOCKOUT_MS = 3000;

WebServer server(80);

bool lastRawState = false;
bool stableState = false;
bool vibrationActive = false;
uint32_t lastRawChangeMs = 0;
uint32_t vibrationStartedMs = 0;
uint32_t lastEventMs = 0;
uint32_t eventCount = 0;

void handleStatus() {
  const char *state = vibrationActive ? "vibration" : "clear";
  String json = "{\"device\":\"sw420_vibration_sensor\",\"state\":\"";
  json += state;
  json += "\",\"vibration_detected\":";
  json += vibrationActive ? "true" : "false";
  json += ",\"event_count\":";
  json += String(eventCount);
  json += ",\"uptime_ms\":";
  json += String(millis());
  json += "}";
  server.send(200, "application/json", json);
}

void handleRoot() {
  String page = "<!doctype html><html><head><meta charset='utf-8'><meta http-equiv='refresh' content='2'><title>Vibration Sensor</title></head><body><h1>SW-420 Vibration Sensor</h1><p>State: <strong>";
  page += vibrationActive ? "VIBRATION DETECTED" : "clear";
  page += "</strong></p><p>Events: ";
  page += String(eventCount);
  page += "</p><p>Machine-readable status: <a href='/status'>/status</a></p></body></html>";
  server.send(200, "text/html", page);
}

void connectWiFi() {
  WiFi.mode(WIFI_STA);
  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
  Serial.print("Connecting to Wi-Fi");
  const uint32_t started = millis();
  while (WiFi.status() != WL_CONNECTED && millis() - started < 20000) {
    delay(250);
    Serial.print('.');
  }
  Serial.println();

  if (WiFi.status() == WL_CONNECTED) {
    Serial.print("Local status page: http://");
    Serial.println(WiFi.localIP());
    Serial.println("JSON endpoint: /status");
  } else {
    Serial.println("Wi-Fi connection failed; sensor detection continues and will retry.");
  }
}

void setup() {
  Serial.begin(115200);
  pinMode(VIBRATION_PIN, INPUT);
  delay(20);

  lastRawState = digitalRead(VIBRATION_PIN) == HIGH;
  stableState = lastRawState;
  lastRawChangeMs = millis();

  server.on("/", HTTP_GET, handleRoot);
  server.on("/status", HTTP_GET, handleStatus);
  server.begin();

  connectWiFi();
  Serial.println("Vibration monitoring is active.");
}

void loop() {
  const uint32_t now = millis();
  const bool rawState = digitalRead(VIBRATION_PIN) == HIGH;

  if (rawState != lastRawState) {
    lastRawState = rawState;
    lastRawChangeMs = now;
  }

  if ((now - lastRawChangeMs) >= DEBOUNCE_MS && stableState != rawState) {
    stableState = rawState;
    if (stableState && !vibrationActive && (now - lastEventMs) >= RETRIGGER_LOCKOUT_MS) {
      vibrationActive = true;
      vibrationStartedMs = now;
      lastEventMs = now;
      eventCount++;
      Serial.println("Vibration detected.");
    }
  }

  if (vibrationActive && (now - vibrationStartedMs) >= EVENT_HOLD_MS) {
    vibrationActive = false;
    Serial.println("Vibration state cleared.");
  }

  if (WiFi.status() != WL_CONNECTED) {
    static uint32_t lastRetryMs = 0;
    if (now - lastRetryMs >= 10000) {
      lastRetryMs = now;
      WiFi.disconnect();
      WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
    }
  }

  server.handleClient();
  delay(5);
}