Sun – Up Alarm
The Sun – Up Alarm can be used to provide a audible alarm for when the sun comes up or it can be used in a dark area and detect when a light comes on. It can also be used to detect a light beam, headlights etc. The circuit works as follows. The phototransistor is very sensitive to light. (Any phototransistor will work fine) The sun shining on this device will provide a high to one of the NAND gates. This will cause another NAND gate to oscillate which will drive another gate to output a 100hz tone. The transistor provides drive for the speaker.
From : http://home.maine.rr.com/randylinscott/jun20.htm
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Categories: Audio diagram, Lighting Tags: light switch, lighting senser, Sun alarm circuit
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