Infrared ray alarm circuit

Published:2011/6/30 3:38:00 Author:Christina | Keyword: Infrared ray, alarm | From:SeekIC

The infrared ray alarm circuit is as shown in the figure. It is composed of the light source, the receiver and the sound and light alarm circuit. There is the infrared receiver in a certain distance from the infrared light source, so there is an invisible infrared cordon between the infrared light source and the receiver. When no one keeps out the infrared ray, the infrared ray irradiates on the photosensitive diode VD1 directly, so the photosensitive diode's resistance becomes smaller to conduct the VT1, the VT2 is in the cut-off state, the relay K which is connected with the collector VT2 will not work, the contact point K1 opens, so the sound and light alarm system has no power voltage to work. Figure The Infrared ray alarm circuit



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