ELECTRICITY GUARD

Who does not know the story of the brave poor man’s Ali Baba from the Arabian tales “Thousand and one night”, who overheard the mysterious words, in pronouncing of which opened a magical door to the treasure cave?

Of course, the magic door, happen only in fairy tales. But safe Deposit boxes, storage of valuable documents in our time are equipped with an ingenious automatic locks, sophisticated alarm systems.

 

The progress of security systems is associated with the birth and development of electrical engineering. Edison himself began his activity with the electrical security system. On his first invention, he said: “Once, when I was a boy, I read in the Newspapers that one robbed the rich man, the banker decided in whatever was to find a means to protect their wealth from further attacks. After a few minutes I was standing in front of a banker.

 

“Sir,” I said, ‘ I’ve just invented a device that in a very short time will betray into your hands of any who try to approach your safes.

 

And how much are you willing to get for your invention? asked the banker,

 

— Hand of your only daughter! I said boldly and decisively.

 

— Well, it’s impossible, but I offer you 10 thousand dollars when you can prove to me the actual benefits of this invention.

 

I agreed. Two days later I went to see the banker and found him lying in bed.

 

— Sir, — I said, — yesterday you wanted to open your safe. But as soon as you touched the castle, you are struck by electric shock is relatively weak, but nonetheless you fell down on the floor. This is my invention. Someone comes after the close of the service to be wowed by the shock and will lie unconscious for as long as you wish”.

 

Since then, much time has passed, science and technology has leaped forward. Now there are many a variety of mechanical, optical, electrical and electronic security systems, successfully coping with the charged matter.

 

A special place is the protection of vehicles against theft and intrusion by unauthorized persons. This worldwide problem has not been fully addressed, although developed and found practical application of many original technical solutions. For example, radiosignalizatsii, consisting of a transmitter, activated when the vehicle door is opened, and the miniature receiver, which is the owner of the motor vehicle; a capacitive relay, triggered by approaching car, or all kinds of electric locks.

 

When choosing a security device always consider such factors as reliability and efficiency. The first is the system’s ability to reliably operate for a long time, the second — the ability to maintain the integrity of the object.

 

In our case the most reliable security device would be apparently normal toggle switch, breaking the ignition circuit of the engine. However, the effectiveness of such a device is very small.

 

Obviously, it is necessary to find a compromise solution that, on the one hand, to reliably protect the vehicle from intruders, and on the other to simplify the structure of the security device.

 

The scheme is one of such devices — in figure 1. There are no transistors, but despite this, the device works quite well. When you turn on guard mode at the same time break the ignition circuit, but when you try an outside person to open the door, the hood or trunk, the siren is activated. It will beep until until the owner disables the alarm or until the battery is exhausted.

 

Fig. 1. The scheme of the “watchman” (1st option).

 

Diagram of the device consists of three components: the time relay containing a chain of delay on energisation R2, C2 and releasing the R1, C1; control relay, connected in series with limit contacts PA doors, trunk and hood; intermediate relay with powerful contacts to activate the sirens.

 

In watchdog mode the device is transferred by pressing the S1 button located on the remote. With this relay K2, cambiocorsa and a contact K2.3 prepares to the action of relay K1. NC contact of K2.2 disables relay. Turning on the switch S5 break the ignition circuit of the engine and the power supplied to the coil K1. 4-5 relay will turn on and “pull” scheme. During this time, you need to get out of the car and shut the door. Now the contact K1.1 discontinued limit switches S2—S4: the scheme is in sentry mode.