Mobile GSM signaling device. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Safety and security

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From other signaling devices that transmit an alarm signal via the GSM network, this one is distinguished by independence from the 220 V network and mobility (it can be installed anywhere). There are systematic monitoring of the health and operation of the cell phone, with which it works, checking the voltage of the battery. When the charger is connected, it will charge automatically.

The signaling device also receives incoming calls, making it possible to listen to the sound environment at the protected facility and notifying with tonal messages about the recorded alarms and the degree of charge of the battery.

The author's copy of the signaling device works with the Motorola C200 cell phone, but you can use another one. The number of the subscriber to be called in case of an alarm (the "master") must be entered into the detector's telephone in advance so that it can be dialed by pressing one of the numeric keys (from "2" to "9"). It is further assumed that the "2" key is selected for the "speed dial" of this number.

Fig. 1

The "Rapid" detector, in conjunction with which the signaling device works, is designed to be powered by a constant voltage of 12 V. In order not to make a separate source of this voltage, the detector needs to be modified. The voltage regulator 78L05, the resistor marked 560 and the diode located next to the detector's terminal block should be removed from its board. Jumpers from an insulated wire connect the contact pads for terminals 1 and 8 of the stabilizer, as well as the upper contact pad for the resistor with the lower pad for the diode. The modified board is shown in the photograph of fig. 1.

The "Tamper" button (above the integrated stabilizer) has also been removed, but this is not required. After such refinement, the detector can be powered by +3...5 V voltage, applying it to the "+12 V" contact of the terminal block.

Rice. 2 (click to enlarge)

The signaling device circuit is shown in fig. 2. The SA1 switch turns off only the power supply of the "Rapid" security detector, and all other nodes, including the cell phone, are continuously supplied with battery voltage GB1. After switching on the detector, the contacts of its output relay are closed. At the input RA0 of the microcontroller DD1, the voltage is set to a low logic level. The microcontroller program counts approximately two minutes of exposure. At the same time, the cell phone is turned on and registered to the network.

Exposure is necessary so that a person, having turned on the alarm, has time to leave the protected area. If within these two minutes the detector gives an alarm signal, the delay countdown will start again. After the expiration of the exposure, using the optocoupler U1, pressing the phone key selected for calling the "owner" is simulated. This call informs him that the signaling device has switched to armed mode.

If the jumper S1 is in position 1-2, the cell phone remains on in armed mode. To turn it off without wasting battery power, the jumper is moved to position 2-3, thus connecting the RA1 input of the microcontroller to a common wire. This should only be done with the SA1 switch open. The change will take effect when you switch to armed mode.

If an intruder moves in the sensitive zone, the Rapid detector relay contacts periodically open, setting a high logic level voltage at the RA0 input of the microcontroller. Having detected this, the program puts the signaling device into alarm mode. Cell phone status is being checked. The signal, the level of which indicates whether the phone is on or off, is taken from the "Call" key, amplified by the transistor VT1 and fed to the input RA3 of the microcontroller. In case of an unsuccessful attempt to turn the phone on or off, the program generates pulses with a frequency of about 4 Hz on the RA2016 pin of the microcontroller, which is configured as an output, and the HA1 piezoelectric emitter gives a continuous sound signal.

If the phone is turned off, the program turns it on and registers it in the network, which takes 50 seconds. After that, if the phone was left on, a call to the "master" is made immediately after the alarm. It lasts approximately 30...40 s depending on the connection time. Then the hang-up is given, and after 15 ... 20 seconds the call is repeated. In total, three calls are made one after the other, and the program checks whether during this time the Rapid detector has been turned off by the SA1 switch. It is considered off if the voltage level at the RA0 input of the microcontroller remains consistently high for more than 5 s. Having discovered this, the program turns off the cell phone as well. Otherwise, the signaling device returns to armed mode. If the alarm is fixed for the second or more times, the HL1 LED turns on.

When the voltage of the GB1 battery drops to 3,7 V, the HL2 LED starts flashing, signaling the battery is low and the need to connect the charger. The continuous glow of this LED indicates that charging is in progress. When the battery voltage reaches 4,4 V, the relay contacts K 1.1 will break the charging circuit, the H1_2 LED will be off, and the HA1 piezo emitter will give two short signals. As soon as the charger is turned off (for example, disconnected from the 220 V network), contacts K1.1 will close again. Recharging can be started at any time by turning on the charger without waiting for the HL2 LED to blink.

The charging control unit can be simplified by removing relay K1 (a jumper must be installed instead of its normally closed contacts), diode VD2, resistors R7, R10 and transistor VT3. But without this node, you will have to monitor the progress of charging yourself in order to turn off the charger immediately after the HL2 LED turns off.

When the detector is armed, the HL1 and HL2 LEDs flash. In alarm mode, they are always on. When the detector is off, the HL1 LED is also off, and the HL2 LED flashes only when it signals a low battery GB1.

When an incoming call arrives on a cell phone, transistor VT2 generates pulses that arrive at the RA4 pin of the microcontroller, configured to accept them as an input. The presence of a call is fixed if the series of pulses lasts more than 10 s. After that, the U3 optocoupler simulates pressing the "Call" key of the phone. Then, for 120 seconds, the microphone works, and by "pressing" with the help of optocoupler U1, tone messages are transmitted to key "2", informing the "owner" about whether an alarm has been recorded and about the charge of the GB1 battery.

The transmission of information starts 3 s after answering the call. Each cycle of its transmission begins with one (there was no alarm) or two (there was an alarm) tones. This is followed by a pause of 3 s and one more (battery is charged) or two (battery is discharged) tone bursts. This cycle is repeated five times with pauses of 13 s. If the "Rapid" detector gave an alarm before the end of receiving an incoming call, the detector immediately hangs up and goes into alarm mode.

The TFM-25F piezo emitter can be replaced by any other piezoelectric emitter without a built-in generator, preferably with a resonant frequency of about 2 kHz. The DA1 microcircuit is a voltage regulator of +2,5 V, which is supplied to one of the inputs of the ADC of the DD1 microcontroller and does not change when the battery GB1 is discharged, along with its supply voltage serving as an exemplary for the ADC of the microcontroller. Based on the results of the ADC operation, the program evaluates the degree of charge of the GB1 battery and determines whether the signaling device is connected to the switched on charger.

In the cell phone selected for operation with the signaling device, it is necessary to turn off the sound accompaniment of pressing the keys, receiving SMS messages and incoming calls. Only the vibrating alert should remain on. In some models of cell phones, you need to enable "speed dialing" of the subscriber's number. The vibration call motor is removed, and wires are soldered to the contacts intended for it according to the signaling device circuit, observing the polarity indicated on it. The wires are also soldered to the contacts of the "Call", "On / Off" keys. and "2" (or the other one chosen for "quick call"). The polarity of the voltage on the contacts of the motor and buttons can be determined using a multimeter.

The battery is removed from the phone. The wire of the "+ U „m" circuit is connected to the contact for the positive output of this battery, and the wire of the "Common." - with a contact for its negative output.

The GB1 battery is made up of three AA Ni-MH batteries. The author used batteries with a capacity of 2500 mAh. The duration of their work after a full charge is at least 14 days with daily arming and disarming of the facility.

Fig. 3

The device is assembled on a prototyping board by wired wiring and placed in a plastic case of a suitable size (Fig. 3). On its front wall there is a detector "Rapid" and LEDs HL1 and HL2. To make the LEDs draw less attention, they can be installed on the right side or on the back wall of the case. On the left side wall are the SA1 switch and the connector for connecting the charger.

The microcontroller program can be downloaded from ftp://ftp.radio.ru/pub/2013/04/MobileGSM.zip.

Author: A. Kovtun

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