A simple but effective DIY anti-theft device. Such a device can be made quite quickly and simply. Complex and expensive parts are not required, but despite this, the device can be very useful in protecting your favorite “horse”. Currently, anti-theft devices have taken the path of complication, and even space technologies are present in their production, but despite this, car security is still relevant. Hijackers are also developing and using the same modern technologies.
Perhaps this simple device will be the tool that will confuse the thief, who expects that there are “cool” anti-theft devices everywhere.
The circuit works like this: the anti-theft is turned on. The attacker opens the door, turns on the ignition, starts the engine and is glad that everything worked out for him. But suddenly the engine stalls. He starts it again, but after 5 - 15 seconds (depending on how you adjusted the anti-theft device), the engine stops again and there is a feeling that there is a problem with the fuel system.But it will not find the fault, since the time relay blocks the engine ignition system with a blocking time delay, and not the fuel system.
The proposed anti-theft device is, in fact, a relay with a time delay to turn on.
Here is his diagram
Parts are used for this device.
- Chip D1 - K176LA7 or its imported analogue CD4011.
- Transistor VT1 - KT315 with any letter or import 2SC634, 2SC633, BFP722, 2N2712, BFP720, BFP721, BFP719.
- Transistor VT2 - KT815 or BD 135, BD 139, BD 137.
- Capacitor C1 - 33 microfarads 25 volts.
- Capacitor C2 – 10 - 20 uF 25 volts. This capacitor is a time-setting capacitor, which means that the time delay before the relay turns on depends on its capacitance. With a 10 μF capacitor, the time is about 7 seconds, and 20 μF is about 15 seconds, but this also depends on the resistor R1, which is also a component of the time-setting chain - R1 - C2, and the time also depends on its resistance.
- R1 - approximately 300 Kom, but I set the potentiometer to 680 Kom in order to be able to demonstrate the change in the time delay before turning on the relay Rel1, depending on the value of its resistance. In the finished device, when you have decided what time delay suits you, the potentiometer can be replaced with a constant resistance equal to the resistance of the potentiometer.
- R2 – 100 Ohm.
- S1 – any toggle switch, switch you like. It will be securely hidden in the car.
- A toggle switch is connected to terminal 1, and the toggle switch is connected to the wire that receives power after the ignition switch is turned on.
- Terminal 2 is connected to the ignition breaker wire. When the device is turned on, the contact of the anti-theft relay will close the breaker wire to ground and thereby turn off the engine.
- Terminal 3 is connected to ground.
- It is better to make a device on a breadboard, it will be easier and faster.
Assembling the device
We solder the wires to the toggle switch and potentiometer and connect them to the circuit.
We connect the finished device to a 12 volt battery.
The anti-theft device is working.
The device board must be placed in the case and filled with sealant to avoid mechanical damage and short circuits.
Watch the video, which shows the dependence of the time delay before turning on the relay on the resistance of the potentiometer.
