Design and manufacture of alarms that are not easily damaged

Probe domestic switch needle KG300B head diameter 3.0 normally closed switch needle total length is 5

Many residential buildings are surrounded by storage rooms. Since the storage room and the living room are not in one place, the owner did not know if the storage room was stolen and the indoor motorcycle was stolen.

Here is a storage room door switch alarm. The alarm has a wire leading from the floor room to the storage room. As long as the owner closes the storage room door back to the floor and turns on the alarm power switch, whether the storage room door is smashed or not, The alarm external line is cut or shorted, and the alarm will send an alarm signal. Therefore, the alarm is not easily damaged, and the owner can find the thief in time.

The alarm circuit is shown in the figure. In the figure, the detection circuit adopts a resistance bridge, the storage room door switch adopts a magnetic control switch, the door is closed, the door is opened and disconnected, and a resistor of the storage room door switch and the bridge constitutes an arm of the bridge and is installed in the storage room. In this way, if the door is opened, the magnetic switch is turned off; if the external line is shorted or disconnected, in either case, the bridge will be out of balance, and the voltage across the A and B passes through the 1N4148 of the rectifier bridge to make the optocoupler. Work, so that the two-way thyristor is turned on, and the bell emits an alarm signal.

The alarm supply voltage is obtained by capacitor step-down, half-wave rectification, and 18V regulator. The door switch can be a normally open type of magnetic control switch, or it can be replaced by other micro switch or micro button. When installed, a bridge arm resistor must be fitted with the switch.

Turn off the power when you don't need an alarm, or you will alarm when you open the storage room door.

There are many types of alarms. According to the different physical quantities detected, they can be divided into: microwave, infrared, laser, ultrasonic and vibration. According to the different transmission modes of electric signals, they can be divided into two modes: wireless transmission and wired transmission. .