How theCellular Alerter/Logger Works

Uses Standard Cell Phone Components



The cellular radio, an 1" by 1" module, is manufactured by SIMCom, a worldwide manufacturer, and meets wireless carrier's communication standards. These three elements, plus supporting components, allows the Alerter to send text messages to cell phones. The same text messages you probably receive daily. Called SMS, for "Short Message Service" is the text communication service component of phone, web or mobile communication systems. SMS can use landline or mobile phone devices. Messages are typically limited to 170 characters. SMS text messaging is used worldwide, with more than 2.4 billion active users. Some users comment that they use their cell phone for texting than they do for voice calls. SMS is the primary communication method of the Alerter. (A data channel also exists - see Logging section.

The SIM card - Pay as You Go

SIM cards are provided by AT&T or T_Mobile cell carriers and allows the Cellular Logger/Alarmer to have a telephone number, a security code, and an authorization code. The card is purchased from T-Mobile, AT&T or us and is installed in our factory or by the customer. The SIM card plugs into the Alerter which is considered an "unlocked" cell phone meaning it can be used with any carrier. Since there is no voice capability, the SIM card can be purchased on a per-message basis making the Alerter inexpensive to operate. For example, if the Alerter sends a daily "all's-well" message at a cost of ten cents per message, that's a monthly cost of about $5.00. See more about this in the SMS tab.

Alarms and Settings
The SIM Subscribe Card

A microprocessor controls the operation of the cell radio and provides the input/output interface to the temperature sensor and the door position sensors and the city power sensor. (Or whatever else is used as a sensor) It also operates the keypad and display and provides an alarm device for alerting that the sensorvalue is changing toward an unsafe level.

The digital temperature sensor is made Dallas Semiconductors, (18b20). This sensor is factory calibrated and can be used with a wide range of cable lengths without the need for re-calibration. It measures Temperatures from -55°C to +125°C (-67F° to +257°F) with ±0.5°C accuracy from -10°C to +85°C. For complete information see 18b20 Datasheet.
The block diagram above shows the elements of the Alarm. the heart of the element is a cellular modem which converts the digital data into modular radio signals. Software controls the modem. A separate logic section continously monitors the alarms and controls the data control when an alarm is sent.