Design of automobile air freshener based on multivibrator

555 time base circuit IC2 and R4, R5, C5, etc. form a multivibrator. After the power is turned on, because the voltage on C5 is very low, the output terminal (pin 3) of IC2 is at a high level and 12V at the same time. The voltage is charged to C5 via R4 and R5, and the voltage on C5 gradually increases. When the voltage on C5 rises to 2 / 3VCC, the internal flip-flop of IC2 flips, pin 3 outputs a low level, and the internal discharge tube turns on, and the voltage on C5 begins to discharge through pin 7 through R5. When the voltage on C5 drops to 1 / 3Vcc, IC2 internal flip-flop flips again, pin 3 outputs a high level, and the internal discharge tube ends, and the 12V voltage is charged to C5 via R4., R5. The oscillation is formed again and again, the oscillation frequency .f = 1.44 / [(R4 + 2R5) C5], and its 3 pin output is about 48k. High frequency pulse voltage of Hz.

When the output end (3 feet) of IC2 is high level, the switch tube VT is turned on, and the 12V power source flows through the primary winding of the transformer T through the diode VD. When the output terminal (pin 3) of IC2 is low level, the switch tube VT is cut off, and the energy stored in the transformer T is released through its secondary. Since the primary and secondary transformation ratio of T reaches 1: 300, the secondary pulse voltage will be as high as 3000V. As described above, the discharge of the tip of the discharger ionizes the air to generate negative ions. The role of fan M is to make negative ions diffuse into the surrounding air faster and better.

The 555 time-base circuit IC1 and R1, R2, and C2 ultra-low frequency oscillators have an oscillation period of about 6 minutes. The output (pin 3) outputs a square wave with a pulse width of 180 seconds and an interval of 180 seconds. The reset terminal (pin 4) of the high-frequency oscillator IC2 is controlled by the output terminal (pin 3) of IC1: IC2 oscillates when the output terminal of IC1 is at a high level; IC2 stops oscillating when the output terminal of IC1 is at a low level, and the output terminal of IC2 is Low level. The result of the joint action of IC1 and IC2 is that the circuit works for 3 minutes, pauses for 3 minutes, and generates negative ions intermittently. The fan motor M is also controlled by the output of IC1 and works synchronously with IC2. The light-emitting diode VD1 is a working indicator light of the negative ion generating circuit. It is composed of another multivibrator, which is an ultra-low frequency oscillator with an oscillation period of about 6 minutes. Its output (pin 3) outputs a square wave with a pulse width of 180 seconds and an interval of 180 seconds. The reset terminal (pin 4) of the high-frequency oscillator IC2 is controlled by the output terminal (pin 3) of IC1: IC2 oscillates when the output terminal of IC1 is at a high level; IC2 stops oscillating when the output terminal of IC1 is at a low level, and the output terminal of IC2 is Low level. The result of the joint action of IC1 and IC2 is that the circuit works for 3 minutes, pauses for 3 minutes, and generates negative ions intermittently. The fan motor M is also controlled by the output of IC1 and works synchronously with IC2. The light-emitting diode VD1 is a working indicator light of the negative ion generating circuit.

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