Published:2011/6/23 20:40:00 Author:Nicole | Keyword: infrared sensor, dangerous voice warning | From:SeekIC
Pyroelectric infrared sensor head is same with the figure. When it detects the human body infrared signal in guarding zone, the sensor head will output a positive jump pulse signal, this signal is added to input terminal P point.
IC1 adopts 555 time base circuit, the monostable trigger circuit is composed of 555 and R3, C2. P's jump signal is phased and amplified by TV1, 555 is triggered by negative jump signal, its output turns to high level, TV2 is saturation conduction, language integrated circuit IC2 is triggered, and it sends out voice warning. The short steady duration time of IC1 monostable is td=1.1R3C2. Adjusting R3 properly, the time can be changed, the graphic parameter is about 12s.
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