Circuit diagram of verbal rescue box for patients who have fainted

The posture switch SK in the figure can be a commercially available mercury switch or a homemade mercury or salt water switch, as shown in Figure a. SK is used to detect the status of the carrier; when stationary, the two electrodes are insulated due to the vertical position; when the person is active, the two poles of the switch will be on and off, which causes VT1 and VT2 to be on and off from time to time. Cut off from time to time. Therefore, C1 connected to the collector of VT2 is sometimes charged and sometimes discharged, but the voltage on C1 never reaches 1.3V, which is lower than the trigger setting voltage of the time base circuit 555 1/3Vdd (2V), that is, the 555 is usually in the set state. bit state, pin 3 is at a high potential, causing VT3 to saturate and conduct, and IC 2 cannot be triggered to make sound. RP1 and C1 form a charging delay circuit. Its function is to prevent the patient from causing the voltage on C1 to exceed 1.3V due to normal activities such as bending over, and to avoid false triggering and alarming.

IC1(555) and R3, R4, C2, etc. form an astable multivibrator. Normally, because the voltage on C2 is lower than 1/3Vdd, the 555 is in the set state, but when the patient slips or falls, SK saturates and conducts VT1, VT2 is cut off, and the charging voltage on C2 can reach more than 2V, causing the D1 reverse bias cutoff. At this time, the 555 oscillator starts to oscillate, and its oscillation period is T=0.693(R3+2R4)C2.

The oscillation period of the parameters shown in the figure is about 50 seconds, and the duty cycle is close to 1:1. During the high level (about 25 seconds), LED1 does not emit light; VT3 is saturated and turned on, and its c-pole low potential (<0.3V) Close pin 4 of the trigger terminal of IC2, and IC2 will not work; during the period when 555 outputs low level, LED1 emits an alarm; at the same time, VT3 is cut off, and the positive jump of its c pole to high potential level triggers IC2, causing IC2 to Work. IC 2 uses the language integrated circuit IVR1601, which includes a clock circuit, a logic control circuit, a flip-flop, a language read-only memory (ROM), and a driver.

The functions and usage parameters of IVR1601 are as follows: working voltage 2.4~6V, working current about 3mA, quiescent current not more than 20uA; has multiple input and output ports; is not afraid of power failure; can store voice signals for about 6 seconds; there are two triggering methods Types: level hold trigger (trigger high level and maintain until the stored content is released) and edge trigger (trigger once, that is, output once);