This circuit activates a buzzer or oscillator when the sensors X1 or X2 are interrupted and with it we can make the protection of doors, windows, objects, fences, etc. The circuit is very simple and very efficient, also serving to protect all the doors and windows of a residence.
The principle of operation is simple: when any of the sensors (X1, X2 and others we can add) is interrupted, the SCR is polarized to the point of tripping via the current through E1 and D1. In these conditions, the buzzer, horn or even other warning device is triggered. Even if the intruder senses the alarm action and tries to re-connect the sensor, it remains triggered. To reset, you must turn the power off and on again.
Powerful buzzers or siresns can be used, horns or even relays to drive systems connected to the power grid.
In figure 1 we have the complete circuit of the alarm and in figure 2 its assembly in a terminal strip.
The SCR is TIC106 and the radiator is required if the load has a current greater than 200 mA. The diode can be 1N4148. The resistor determines the power consumption at rest.
The sensors consist of very thin pieces of wire connected at the protection points.
Material list
SCR- TIC106 - Silicon Controlled Diode
D1- 1N4148 - general purpose diode
R1 - 100k ohm x 1/8 W- resistor (brown, black, yellow)
B1- 6 to 12 V - battery or source
S1- Single switch
Miscellaneous: terminal bridge, wires, solder, etc.
