Earthquake is a terrible natural disaster, which often happens in the middle of the night when people are asleep, making it impossible to prevent. This paper introduces an earthquake audible and visual alarm suitable for family use. When an earthquake happens, it will send out loud sirens and lights so that people can move to a safe place as soon as possible.

First, the working principle

The seismic audible and visual alarm circuit is shown in figure 1. Seismic detection switch SQ, unidirectional thyristor VS, resistor R 1, etc. Forming an electronic switch; Integrated circuit a, transistor VT 1, VT2, speaker b, etc. Form an analog siren sound response circuit, and H is a small light bulb.

When an earthquake of magnitude 4 or above occurs, the detection switch SQ will open with the shaking of the earth. At this time, the 4.5V battery triggers the one-way thyristor VS to turn on through R 1 and SQ. Once VS is turned on, this state will be maintained, and the small electric bead H will be electrified to emit light; At the same time, the integrated circuit A is powered on, and its output terminal outputs an electric signal simulating the siren in the memory, which is amplified by a direct-coupled power amplifier composed of transistors VT 1 and VT2, and then pushes the speaker B to give out a loud alarm sound.

In the circuit, R2 is the external oscillating resistance of integrated circuit A, and the alarm rate can be adjusted by changing its resistance. SB is the alarm signal release button switch.

Second, component selection.

Choose KD-956 1 four-tone analog sound integrated circuit. Integrated circuits are in the form of flexible packaging. The chip size is 32.5mm× 10mm, and the shape is shown in the left figure of Figure 2. Where SEL 1 and

SEL2 is two sound selection terminals. When SEL 1 is connected to VDD and SEL2 is suspended, A outputs an alarm; When SEL 1 is connected to VSS and SEL2 is also connected to VSS, it is an ambulance sound; When SEL 1 hangs, and

When SEL2 is connected to VDD or VSS respectively, it will emit machine gun sound and fire truck sound respectively. In the circuit of figure 1, we chose the siren. Readers can also choose any one of the other three sounds and just change it.

SEL 1 and SEL2 can be connected.

VS selects ordinary MCR 100-6 or BT 169, 2N6565 small plastic sealed unidirectional thyristor (also known as unidirectional thyristor). VT 1 uses 90 14 or 3DG8 silicon NPN low power transistor, and requires current amplification factor β > 50; VT2 adopts 3AX8 1 type germanium PNP medium power transistor, and requires β > 30.

R 1 and R2 both use RTX- 1/8W small carbon film resistor. H Use 3.8V and 0.3A small electric beads for commercial flashlights. B. Use 8 Ω, 0.25W small-caliber dynamic speaker. SB adopts small self-reset normally closed button switch, and can also be replaced by general single-pole single-throw switch. G is composed of 3 No.5 dry batteries connected in series (supporting plastic battery rack), and the voltage is 4.5V.

Iii. Production and use

Fig. 2 shows the wiring diagram of the printed circuit board in the earthquake audible and visual alarm. The printed circuit board is made by cutting, and the actual size is about 34 mm × 40 mm; There is no need to punch holes in the printed circuit board, and components can be directly welded on the surface of copper foil. The integrated circuit A is connected with the printed circuit board made by ourselves through four hard wires. Special attention should be paid when welding: the shell of electric soldering iron must be well grounded to avoid AC induced voltage from penetrating the inside of integrated circuit A.

CMOS circuit!

Figure 3 shows the outline of the earthquake audible and visual alarm. Among them, the seismic detection support requires sufficient sensitivity. The metal hammer of the detection switch can be an electroplated metal wire hammer used by construction workers to hang vertical lines, and a metal ring can also be used.

2mm galvanized iron wire bending. The distance between the heavy metal hammer and the metal ring is adjusted by lifting the heavy metal hammer, which is generally adjusted to1.5 ~ 2.5 mm. The smaller the distance, the higher the alarm sensitivity. In addition, in order to ensure sufficient alarm sensitivity, the height of the metal weight bracket should not be lower than1m.

When in use, put the alarm in a place where the bedroom is not easily disturbed by other external vibrations or wind, and connect the battery, and the circuit will enter the state of monitoring earthquakes, at which time the circuit consumes almost no electricity. If the circuit is triggered by mistake, the audible and visual alarm signal can be released by pressing the alarm release button.