If you suddenly urgently need to take the premises under protection, but there is no alarm system, then this is not a problem. The simplest GSM alarm, and even with a motion detector, can be made yourself from an old mobile phone. The circuit is very simple, even a novice electronics technician can handle its assembly.
Will need
Security system diagram
Power supply 5 - 9 V. It is not necessary to use a crown; you can use a stationary charger for the same mobile phone.
The operating principle is very simple. Almost every push-button cell phone has a speed dial function (you can set it up in the phone menu). This is when one button is pressed and while holding it, the number stored for this button is dialed from memory.
So, in the settings we will write down our number on another phone. We will connect contacts to this button that will go into the circuit. As soon as the sensor detects movement in the room, it will send a signal to the transistor, which in turn will close the cell phone button and an outgoing call will be made to your smartphone. As a result, you will be notified of movement at the protected facility.
How to make a security system with a motion sensor from a push-button mobile phone
We disassemble the cell phone and, using a utility knife, cut off the top contact of the button and bend it.
Next, using a soldering iron, solder two thin wires to the button contacts.
We assemble the mobile phone by first making a slot in the case for the wires. Let's put together a simple circuit.
Connect the 9 V power and check the operation. As soon as a person or part of him enters the field of view of the sensor, the security system will work.
And your smartphone will ring an incoming call.
How to activate the system and leave the room without the alarm going off?
If you apply power to the system, then after 1-2 seconds the sensor will be ready for operation and will be able to detect movement in the room. This may not be enough time to go out and close the door. To increase this time, do this: turn off the cell phone, turn on power to the system. And when you are ready, press the power button on your mobile phone. While it loads and shows splash screens, and then searches for the network, you will have about 5-10 seconds. And this time is quite enough.
