Here is a circuit which will automaticaily light your porch light or activate any other device when the ambient light drops below a certain level.
A ·light dependent resistor is used in series with a relay. The resistor has a value in excess of ‘l megohm when illuminated, this drops A7 to below 110 ohms when day light. It is important that the LDR be positioned in such a place as not to receive any spurious illumination as this will cause the relay to drop out intermittently. A bimetallic strip type relay will give sufficient delay to ensure that incident light flashes have no influence.
Automatic Day/Night, Twilight Switch Circuit
A ·light dependent resistor is used in series with a relay. The resistor has a value in excess of ‘l megohm when illuminated, this drops A7 to below 110 ohms when day light. It is important that the LDR be positioned in such a place as not to receive any spurious illumination as this will cause the relay to drop out intermittently. A bimetallic strip type relay will give sufficient delay to ensure that incident light flashes have no influence.
Automatic Day/Night, Twilight Switch Circuit
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