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
R2: 100
R3: 100
R4: 220
BZ1: horn of the car.
pcb expensive components print
