The Geo-Sentry is a programmable real-time event recording and display system. It interrogates a series of small seismic sensors to detect foot or vehicle traffic. The system was designed to monitor these sensors and send X-10 commands when the level of activity from a sensor indicated a person was walking in the area or that a vehicle was moving in the driveway. By associating a different X-10 command sequence and on -time with each sensor, the outdoor lighting near the driveway and house can follow a person’s movement. This adds safety for the individual and security for the homeowner.

The time resolution of 60 samples per second was selected to facilitate correlation of signals from multiple sensors. This correlation may be able to locate a person within the sensor array. The time field includes the full date and time of the event so long term storage of events can be time tagged with the date as well as time of occurrence. Selected data is recorded at a maximum of the 60Hz rate in a 32K byte circular buffer which then can be dumped to a computer for analysis or printing. The type of data stored and the rate at which it is stored can be tailored by the operator to configure the device to capture short term or long term events.

The unit includes a florescent display to display events as they happen. Copies of events can also be sent to a printer port to produce a hard copy. The Geo-Sentry has a PC interface that allows all the operating parameters to be customized for each installation. This interface allows the operator to associate names with each sensor, define an alarm level for each sensor and assign X-10 commands to the alarms.

The operator can configure the Geo-Sentry to store selected types of data and then later dump this data to a PC in a text format. This data can then be used to perform correlation tests or to examine activity that occurred in the sensor array.

The processor in the Geo-Sentry is the Philips 80C451 which has seven 8-bit I/O ports. Currently the device has 16 sensor inputs implemented but four I/O pins are yet unused so up to 20 sensors could be accommodated. The sensors are Geophone sensors that were designed to perform seismic surveying. The output from these sensors is converted to a pulse stream that is counted by the Philips processor. The microprocessor stores data in a 32K byte SRAM memory that is plugged into a Dallas Semiconductor SmartWatch socket. This SmartWatch provides battery back-up to the memory and also incorporates a real-time clock. It is this clock that is used to time tag all data. Program memory is an external EPROM. The X-10 interface is accomplished using a TW523 interface module which allows the Geo-Sentry to both read and write X-10 commands. The commands read from this interface are available for storage just as the other event data.

The Geo-Sentry is currently monitoring a series of seismic sensors but the real power of the device is in the real-time recording and display software. This system can easily be adapted to monitor any of a number of different sensors. Future projects will examine extending this device into different applications and different implementations.