Alarm for the car

We now have an alarm simple, affordable and easy to use. Uses very few components, only 10, this will truly believe that, economically.

This circuit uses a unijunction transistor (UJT), as a timer, periods of power - off are determined by R1 and C1, with a delay of 10 seconds of the alarm, you need that R1 is 33 kW. When the UJT is commuted there is a pulse output through the capacitor C2, which triggers the SCR1, this in turn activates the horn of the car, or a more complete circuit of alarm.

R4 is an element of retention of the leadership of SCR1, taking into account that the horns of the cars are formed by a vibrator that interrupts the voltage, this would result in the SCR1 is switched off. S1 is the switch that is used to control the alarm and must hide so that only the driver knows where he is.

List of components
Capacitors:
C1: 100 µF 25 V. (electrolyte)
C2: 10 µF 25 V. (electrolyte)
Transistors:
Q1: 2N2646 2N3706 (NTE6401)
SCR1: NTE5501
Resistors:
All of a 1/2 Watt R1: 33K Ω
R2: 100 Ω
R3: 100 Ω
R4: 220 Ω
BZ1: horn of the car.

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