Simple alarm system with their own hands

If you have a car, then you definitely need a alarm system. But to install alarm systems can not buy the device and its forces. What features can we expect from alarm: Alarm must respond to the invasion, for example, passive infrared motion detector. Alarm should be alert about the invasion by the sound. This alert should not act for a long time, that is, no more than five minutes, and then switched off automatically. Once the alarm system worked, she once again must go in standby. And if you want, then the system must be repeatedly triggered. Alarm should consume low current for long-term process of their work. So, to make a simple alarm, will require the following: A motion sensor (passive and infrared), such as OBI sensor is light switch. Siren for 12 volts. In this example we will use the model to 105dB, there are other possible models. Another detail: The relay for 6 volt, battery holder, duct insulation and wires. Assembling the transducer. Necessary to make the motion sensor could not eat from 220 volts and from 12. But this average value. The system will operate within a 7-30 Volt. When eating in a 12-volt relay should have power at 6 volts. Need to open the sensor. Spherical part of the clean, tilting one support. Halves are attached by snap. Pull charge. Sensor - a passive infrared receiver, which responds to changes in infrared radiation impinging on it. Angle of view of our sensor is 180 degrees. Left of the points are served food. "+" - The positive pole of power, "-" - negative. Right-connect switch, which is being dismantled. Relay deduce inside the base housing. The sensor is powered through the switch. At operation, he gives the voltage across the relay coil. The relay is triggered, the contacts are closed, so turn on the siren. Thanks to the relay it is possible to connect not just one but a few sirens. From below it looks like. Via terminals connected batteries and a siren. Bottom left - the relay, and switch - the right. In no case can include a siren, if not protected by the ears. It may, let's not serious, but still damage your hearing. With the help of the regulator can set the time of the siren. It can continue to operate for 10 seconds - 8 minutes. The sensor is placed inside the car, and derive a siren on the street. If you apply power, the system works, so it is best to withdraw the siren switch to a secret location. It should include at 5 minutes after shutting down. The key can commute like the ignition switch the car. Sensor is economical. Standby - 0.7 mA, mode operation - 1.1 mA, and the most current siren - 0,2 A. The sensor can also operate in the winter. It was verified that it accurately maintains temperature equal to -32 degrees, maybe less. Our sensor has drawbacks - it is triggered false if there is water reflections, but the tape can glue the sensor so that it has formed the blind zone.