Publication of Electronic Circuits

Alarm lights of the car

Diagram of Alarm lights of the carIf indeed all or nearly all, we left the lights switched on the car and when we returned it is likely that the battery is discharged, here's an alarm that will leave us no longer do so.

OPERATION: This alarm is basically an a oscillator transistor when we apply the battery voltage (battery), only the issuer of Q1. The battery voltage is applied from 2 possible places in the car, which are lit from the (startup) or from the lights, sometimes this voltage is applied from one or 2 options.

As we shall see in the diagram are in S1 and options Reverse Direct. When funcionade directly wel battery voltage comes from the ignition system flows into the collector and the lights to the issuer, if the switch is connected and turned on the lights of the car are lit at once, both the collector and the issuer are at the same potential, under these conditions the circuit and does not ranged therefore does not sound the alarm; If you turn off a vehicle and left the lights switched on the collector is connected to earth through deT1, R2 and C2, and Developing the voltage negative bias is needed to swing the circuit, if the lights are switched off, it removes the power to the circuit and therefore cease to function.

D1 protects Q1 from reverse voltages that may arise from the battery.

If we want to work on a way around the circuit (ie, leaving the lights on when the vehicle is off, this will not work with the alarm, until the vehicle is started), the S1 is simply inserted in the corresponding position (Inverso); in this position, is completely disconnected voltage of the circuit and while the lights are switched on the alrma not work, but if, when you start the car, as the voltage you apply to the issuer in Q1, is in position for the alarm desconetar it simply passes the S1 to sisntema direct it.

List of components:
C1: 0.22 µF. Ceramic 25-volt
C2: 30 µF. Electrolyte 25 volts
D1-D2: 1N34 (NTE 109).
Q1: 2N217 (NTE 102A)
R1: 15K Ω 1/2 W.
R2: 680 Ω 1/2 W.
T1: audio output transformer with the primary referral center and 400 ohms, 8 ohms secondary You can try another that comes closest to the proposed ohms.
S1: 2-pole switch 2 positions.
8-ohm loudspeaker.
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