Earthquake sensor

MODEL: BREAKOUT019


Breakout board based on the D7S produced by Omron, the smallest seismic sensor in the world. The D7S is composed of a three-axis accelerometer, of which only two are used during the detection of an earthquake and are selectable both by the user and automatically with respect to the inclination of the sensor. 
The D7S SDA, SCL, SET, INT1 and INT2 pins are available on the 6-pin connector strip; while three status LEDs (power, INT1 and INT2 pins) are mounted on the breakout. The I²C bus allows you to change the sensor settings, or read data relating to earthquakes, by any microcontroller that is equipped with this bus and also by Arduino. The SET pin can easily be connected to a button, without having to worry about the pull-up resistor because it is already set in the breakout, and can be used to bring the sensor into initial installation mode simply by pressing it, consequently avoiding having to use the I²C bus. The connection with Arduino is very simple, in fact you simply need to connect the sensor power pins (VCC and GND) with the Arduino 5V and GND pins and the SDA and SCL pins (in Arduino UNO the pins used for the I²C bus are respectively A4 and A5).
Arduino also allows interrupt management, a very useful feature to combine with the sensor presented because it allows you to react instantly to the events generated by the D7S. To use it, simply connect pins 2 and 3 of the Arduino with pins INT1 and INT2 and record the execution of the ISR (Interrupt Service
Routine) on pin 2 when the FALLING event occurs (that is, the transition from high logic value to low logic value), while that on pin 3 when CHANGE occurs (both high-low and low-high logic transitions). Power Supply: 3.3V to 5V

Attention: The connector strip must be soldered.


The D7S Sensor
 
One of its most important features is the signaling, through pin INT1, of seismic events that could have catastrophic effects on electronic equipment; this function allows for example to switch off the equipment before the vibrations caused by the earthquake
could actually cause such damage. The safeguarding of the equipment is essential to be able, after a seismic event, to still have functional equipment to prevent further damaging events. Moreover, the signal obtainable from contact INT1 could be used to trigger alarms and, why not, to activate forms of mechanical protection of measuring instruments and rooms that house them.
There are two signals that the sensor emits: ground shutoff and collapse; the first situation occurs if the earthquake is judged to have an intensity equal to or greater than 5 in the intensity scale of the JMA (Japan Meteorological Agency) and respects the conditions defined by JEWA (Japan Electrolyzed Water
Association standard JWA) in standard JWDS 0007, appendix 2, while the second occurs if the ground undergoes an inclination of approximately 20°. 
 

Summary description of the block of registers containing information on earthquakes.

The sensor also has an internal memory in which data relating to the last five recorded earthquakes and the five largest ones are stored, as well as, of course, all the configuration settings. The D7S is composed of a three-axis accelerometer, of which only two are used during the detection of an earthquake and are selectable both by the user and automatically with respect to the inclination of the sensor. The presence of an I²C bus allows you to change the sensor settings, or read data relating to earthquakes, by any microcontroller that is equipped with this bus and also by Arduino. The D7S sensor has a total of three function pins, two of which (INT1 and INT2) are signaling pins and the third (SET) is a line used to vary the operating status. Before using the sensor, the initial installation procedure must be performed, i.e. the sensor must detect offsets
of the selected axes and save the value in the internal memory; these offsets will be used to discriminate the collapse condition, comparing them with the current ones at the time of detection of the seismic event.
After the initial installation phase the sensor goes into standby until the onset of an earthquake, when the calculation of earthquake data begins; it remains in this state until the end of the earthquake has been judged. At this point the internal memory is updated with the data of the recent detection.
Each time the sensor is powered up, it goes into offset detection mode and determines if the collapse condition has occurred and, if so, varies the logic condition of pin INT1 bringing it to the low level. If the condition is not verified, the sensor goes into standby mode and the earthquake detection cycle begins.
 

Summary description of the status and configuration registers

 
It should be specified that the collapse condition is not discriminated only when the sensor is switched on, but whenever the sensor enters standby; in fact, it remains possible to override the collapse condition by bringing the sensor to the offset acquisition mode.
The data that the sensor calculates for each seismic event are PGA (Peak Ground Acceleration), SI (Spectral Intensity) and the average ambient temperature at which the event occurred. During the calculation, i.e. during an earthquake, it is possible to read the instantaneous value of PGA and SI by accessing some specific registers.
A self-diagnostic function has been implemented inside the sensor, very useful for verifying if the D7S is working correctly, but the same must be activated manually by writing a register using the I²C bus. At each offset acquisition operation, the sensor automatically determines whether the operation was successful, otherwise it updates a specific register, consequently signaling the failure.
The functional pins of the sensor are INT1, INT2 and SET: the first corresponds, as already highlighted, to the signaling of the shutoff and collapse conditions while INT2 allows to know if the sensor is in standby, if the sensor is in the detection phase of an earthquake, if an offset acquisition operation is in progress or if the self-diagnostic function has been activated.
The last pin, SET, allows to bring the sensor, through an external impulse, in initial installation mode, without necessarily having to resort to the use of the I²C bus. When the INT1 pin is driven low by a shutoff or collapse event, the default value of logic 1 can only be restored by reading the EVENT register, performing the initial setup procedure, or removing power to the sensor.
 
Breakout boards
 

The breakout boards are prototyping boards containing the interested component already soldered, whose connections are brought outside the bases on connections that are easily usable for step and termination; generally the connections are 2.54 mm pitch pads, like those of the classic DIP integrated circuits. To facilitate those who would like to use SMD components but do not have the means or the qualities to solder them, a certain number of ICs have been identified (including sensors, switching power supplies, battery chargers, linear amplifiers, etc.), and mounted on ready-to-use bases. These breakout boards are both an aid for those who want to have the best of SMD electronics ready in a "traditional" format, and for those who - while managing to work with SMD components - need to have these components available on prototyping boards to apply them to existing circuits and carry out tests, i.e. to create prototypes that integrate the functions of the relative integrated circuits, before realizing the final printed circuit of an equipment.
 




 

 


 

  
 

 






 

 

  
 

 

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The breakout boards are prototyping boards containing the interested component already soldered, whose connections are brought outside the bases on connections that are easily usable for step and termination; generally the connections are 2.54 mm pitch pads, like those of the classic DIP integrated circuits. To facilitate those who would like to use SMD components but do not have the means or the qualities to solder them, a certain number of ICs have been identified (including sensors, switching power supplies, battery chargers, linear amplifiers, etc.), and mounted on ready-to-use bases. These breakout boards are both an aid for those who want to have the best of SMD electronics ready in a "traditional" format, and for those who - while managing to work with SMD components - need to have
The breakout boards are prototyping boards containing the interested component already soldered, whose connections are brought outside the bases on connections that are easily usable for step and termination; generally the connections are 2.54 mm pitch pads, like those of the classic DIP integrated circuits. To facilitate those who would like to use SMD components but do not have the means or the qualities to solder them, a certain number of ICs have been identified (including sensors, switching power supplies, battery chargers, linear amplifiers, etc.), and mounted on ready-to-use bases. These breakout boards are both an aid for those who want to have the best of SMD electronics ready in a "traditional" format, and for those who - while managing to work with SMD components - need to have