The Sun - Up Relay Switch can be used to provide a audible switch for when the sun comes up. It can also be used to detect a light beam, headlights etc.
This circuit is easy because it used one Transistor 2N2222-2SC945-2SC828-BC549 etc , Relay and Photo transistor Only. The important part of the circuit is [...]
The first circuit energizes the relay when the light rises above the preset level. The second circuit energizes the relay when the light falls below the preset level. The two circuits are practically identical. The only difference between them is the polarity of the transistor. The value of the LDR is not critical. The important [...]
The light sensor used is the ORP12 photocell. In bright light the resistance of the ORP12 can be as low as 80 ohm and at 50lux (darkness) the resistance increases to over 1 Mohm. The 1M control should provide a wide range for light intensities, if not its value may be increased. The op-amp senses [...]
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