Simple GSM-alarm system from scrap materials
The other day we were approached by an old friend. He lives in a private house and a couple of times unknown persons tried to visit him without an invitation. There is a need to install an alarm. Putting a house on the remote turned out to be too expensive. The best solution seemed to be just to notify the owner with a call to a mobile phone when one of the motion sensors was triggered.
First we visited the local shops selling security alarms. However, prices for the most budget GSM-devices were bitten - from 5 kilorubles per unit. Therefore, we decided to build a GSM-alarm system with our own hands.
We had a Nokia 1600 mobile phone with an off screen backlight (a chronic malfunction after bathing with this model) and a 12 volt power supply. Only the cheapest volume Astra detectors (200 rubles each), a 12 volt battery with a capacity of 7.2 Ah (another 400 rubles), a few meters of four-wire installation wire (~ 50 rubles) and a cyclic daily timer (250 rubles) had to be bought.
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We have chosen the following logic of the alarm. When at least one of the volume workers triggers, the call button starts to “push” (the green handset on the device). On Nokia phones, the first press draws the last number dialed to the screen, the second makes a call to that number. Subsequent presses do not affect the operation of the phone.
To implement the planned algorithm, a simple scheme was compiled on the national logic.
This is the simplest pulse generator. With the indicated ratings, R1 and C1, the pulse frequency is about 1 Hz. The generator load is an optocoupler. We pulled it out of the computer power supply. The right part of the optocoupler is connected to the contacts of the button for calling a mobile phone. To do this, the phone is opened, the contactor of the button is removed, and thin wires are fed into the contacts.
Parallel to the wires included clock button. It is needed to configure the system.
The volume selectors we chose in normal condition (no alarm) have at the output relays with normally closed contacts, which break the circuit when the device is activated. We used this to control the click generator.
The output of the volumetric arrays is turned on in parallel with the optocoupler and, in the protection mode, simply short the generator output to the ground. The current limiting resistor becomes the only load on the generator. When the circuit is open, the current goes through the optocoupler and the system starts to work.
Now about setting up a mobile phone. Auto-lock the keyboard to turn off. Clear all calls log, set call forwarding of all voice calls to MCA number - Missing Call Alerting (“You have been called” service). This is important; otherwise, a situation where the system will answer a random incoming call instead of a call to the owner’s phone is not excluded. Then you need to dial the number of the owner and press the rendered call button. If everything is assembled correctly, the owner's phone will ring.
Our civilians support only one logic of work: after the triggering, the alarm loop is opened for one minute. During this time, the phone will try to reach the owner. Detach from him is impossible.
The outputs of the relay several volumnikov should be included in the alarm loop in series. Then, if any of them is triggered, there will be an alarm in the circuit. The number of connected volumnov is limited only by the resistance of the wire.
Energy generator and volunteers receive from the power supply at 12 volts. The phone runs on its own battery, the timer is turned on only once a day (for an hour and a half, it is selected experimentally), which recharges the phone through a standard charger.
The arming and disarming of the device is carried out with a masked switch inside the controlled room. Thus, the “alarm setting” mode is performed. This is convenient, the performance of the system is checked every time before turning it on.
An extended version of this alarm has a power reserve due to the battery. In our case, the 12-volt battery is connected in parallel to the main power supply. The power supply turns on through the diode. It prevents the battery from discharging through the power supply when it is de-energized.
Thus, if you have an old phone and direct hands, you can get a suitable GSM detector worth less than a thousand rubles. Our system works with a friend without any complaints, does not give false alarms. For convenience, he even put a separate ringtone in the form of a siren for an incoming call from the system.
First we visited the local shops selling security alarms. However, prices for the most budget GSM-devices were bitten - from 5 kilorubles per unit. Therefore, we decided to build a GSM-alarm system with our own hands.
We had a Nokia 1600 mobile phone with an off screen backlight (a chronic malfunction after bathing with this model) and a 12 volt power supply. Only the cheapest volume Astra detectors (200 rubles each), a 12 volt battery with a capacity of 7.2 Ah (another 400 rubles), a few meters of four-wire installation wire (~ 50 rubles) and a cyclic daily timer (250 rubles) had to be bought.
')
We have chosen the following logic of the alarm. When at least one of the volume workers triggers, the call button starts to “push” (the green handset on the device). On Nokia phones, the first press draws the last number dialed to the screen, the second makes a call to that number. Subsequent presses do not affect the operation of the phone.
To implement the planned algorithm, a simple scheme was compiled on the national logic.
This is the simplest pulse generator. With the indicated ratings, R1 and C1, the pulse frequency is about 1 Hz. The generator load is an optocoupler. We pulled it out of the computer power supply. The right part of the optocoupler is connected to the contacts of the button for calling a mobile phone. To do this, the phone is opened, the contactor of the button is removed, and thin wires are fed into the contacts.
Parallel to the wires included clock button. It is needed to configure the system.
The volume selectors we chose in normal condition (no alarm) have at the output relays with normally closed contacts, which break the circuit when the device is activated. We used this to control the click generator.
The output of the volumetric arrays is turned on in parallel with the optocoupler and, in the protection mode, simply short the generator output to the ground. The current limiting resistor becomes the only load on the generator. When the circuit is open, the current goes through the optocoupler and the system starts to work.
Now about setting up a mobile phone. Auto-lock the keyboard to turn off. Clear all calls log, set call forwarding of all voice calls to MCA number - Missing Call Alerting (“You have been called” service). This is important; otherwise, a situation where the system will answer a random incoming call instead of a call to the owner’s phone is not excluded. Then you need to dial the number of the owner and press the rendered call button. If everything is assembled correctly, the owner's phone will ring.
Our civilians support only one logic of work: after the triggering, the alarm loop is opened for one minute. During this time, the phone will try to reach the owner. Detach from him is impossible.
The outputs of the relay several volumnikov should be included in the alarm loop in series. Then, if any of them is triggered, there will be an alarm in the circuit. The number of connected volumnov is limited only by the resistance of the wire.
Energy generator and volunteers receive from the power supply at 12 volts. The phone runs on its own battery, the timer is turned on only once a day (for an hour and a half, it is selected experimentally), which recharges the phone through a standard charger.
The arming and disarming of the device is carried out with a masked switch inside the controlled room. Thus, the “alarm setting” mode is performed. This is convenient, the performance of the system is checked every time before turning it on.
An extended version of this alarm has a power reserve due to the battery. In our case, the 12-volt battery is connected in parallel to the main power supply. The power supply turns on through the diode. It prevents the battery from discharging through the power supply when it is de-energized.
Thus, if you have an old phone and direct hands, you can get a suitable GSM detector worth less than a thousand rubles. Our system works with a friend without any complaints, does not give false alarms. For convenience, he even put a separate ringtone in the form of a siren for an incoming call from the system.
Source: https://habr.com/ru/post/130842/
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