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
Related Links
Lighting Sensor circuits
Light Switch
Sun alarm circuit
Emergency Light
Dimmer Lamp LDR control with Triac.
Audible Light Sensor by IC 741
This entry was posted on Wednesday, April 11th, 2007 at 2:11 pm and is filed under Audio - Alarm, Lighting.
