In this project I show how to make a door open or tailgate down sensor using an Arduino vibration sensor and
Reed switch
Below is the sketch I used, running on the Arduino Uno:
#define VIBRATION_SENSOR_DIGITAL_INPUT_PIN 10 #define VIBRATION_SENSOR_DIGITAL_OUTPUT_PIN 8 #define REED_SWITCH_DIGITAL_INPUT_PIN 6 #define VIBRATION_EVENTS_ALARM_THRESHOLD_COUNT 5 #define VIBRATION_EVENTS_ALARM_THRESHOLD_PERIOD_MILLIS 5000 #define VIBRATION_ALARM_FLASHES 5 #define VIBRATION_ALARM_PERIOD_MILLIS 400 long vibrationEvents[VIBRATION_EVENTS_ALARM_THRESHOLD_COUNT]; int vibrationEventIndex; //------------------------------------------------------------------ void setup(){ Serial.begin(19200); pinMode(VIBRATION_SENSOR_DIGITAL_INPUT_PIN, INPUT); pinMode(REED_SWITCH_DIGITAL_INPUT_PIN, INPUT); pinMode(VIBRATION_SENSOR_DIGITAL_OUTPUT_PIN, OUTPUT); vibrationEventIndex = 0; clearVibrationEvents(); } //------------------------------------------------------------------ void loop(){ // only pay attention to vibration when the Reed switch is open if(digitalRead(REED_SWITCH_DIGITAL_INPUT_PIN) == HIGH && digitalRead(VIBRATION_SENSOR_DIGITAL_INPUT_PIN) == HIGH){ addVibrationSample(); delay(100); // debounce current vibration shock } } //------------------------------------------------------------------ void addVibrationSample(){ vibrationEvents[vibrationEventIndex++] = millis(); // wrap index around end of sample array vibrationEventIndex %= VIBRATION_EVENTS_ALARM_THRESHOLD_COUNT; if(isVibrationAlarmTiggered()){ Serial.println(String(millis()) + "\t ALARM"); triggerAlarm(); } } //------------------------------------------------------------------ boolean triggerAlarm(){ for(int i = 0; i < VIBRATION_ALARM_FLASHES; ++i){ digitalWrite(VIBRATION_SENSOR_DIGITAL_OUTPUT_PIN, HIGH); delay(VIBRATION_ALARM_PERIOD_MILLIS/2); digitalWrite(VIBRATION_SENSOR_DIGITAL_OUTPUT_PIN, LOW); delay(VIBRATION_ALARM_PERIOD_MILLIS/2); } clearVibrationEvents(); } //------------------------------------------------------------------ void clearVibrationEvents(){ for(int i = 0; i < VIBRATION_EVENTS_ALARM_THRESHOLD_COUNT ; ++i){ vibrationEvents[i] = -1; } } //------------------------------------------------------------------ boolean isVibrationAlarmTiggered(){ long thresholdMillis = millis() - VIBRATION_EVENTS_ALARM_THRESHOLD_PERIOD_MILLIS; if(thresholdMillis < 0) thresholdMillis = 0; int numVibrationsSinceThreshold = 0; for(int i = 0; i < VIBRATION_EVENTS_ALARM_THRESHOLD_COUNT ; ++i){ if(vibrationEvents[i] >= thresholdMillis){ ++numVibrationsSinceThreshold; } } Serial.println( String(millis()) + "\t# events: " + String(numVibrationsSinceThreshold)); boolean alarmTriggered = false; if(numVibrationsSinceThreshold >= VIBRATION_EVENTS_ALARM_THRESHOLD_COUNT){ alarmTriggered = true; } return alarmTriggered; } //------------------------------------------------------------------
If you are interested in how this type of sensor can be integrated into a broader solution that includes notification of a door open on a users Android phone see Detect if a Door or Gate is Opened
watches for vibration events but only triggers if it sees 5 vibration events within a 5 second period. So if it gets 3 events and then none for a while it will forget those 3 events. Only if it gets 5 or more within 5 seconds will the alarm trigger. This effectively screens out spurious bumps and fires on persistent vibration events. This can be useful for a variety of applications where was is sought is the ability to detect vibration rather than a single bump. The values for the number of events (5 in my sketch) and period of time (5 seconds) are configurable by changing the values at the top of the sketch for your project.
and the
. If you want to see how to do GPS location sensing with the Arduino Uno and an LCD display check out my other 
connected. This is very important as you can't get a location fix if you don't have an antenna.
to sense location in terms of latitude and longitude coordinates.
