The following explained automatic day night switch circuit using a Bi-Metal strip and an LDR is able to automatically illuminate your porch light or power up some other equipment once the ambient lighting falls below the specific intensity. A ·light dependent resistor is employed in sequence with a relay. The resistor possesses a value above 1 megohm the minute switched on, this goes down A7 to below 110 ohms in case of a day light. It is imperative that the LDR be placed in sort of a location as not to pick up any kind of spurious luminosity because this will result in the relay to give up sporadically. ' A bimetallic strip type relay will offer ample delay to make sure that incident lights flashes never have any sort of impact.
Automatic Day/Night Switch Circuit using Bi-Metal Strip and LDR diagram can be see in the following section