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Friday, September 24, 2010

Light detector using a relay

Following circuit is same as the above mentioned dark detector. In this case, the configuration of relay has been changed. Now, NO (Normally open) terminal has been left open. In normal case, the D1-LED remains ON. When light falling on LDR is interrupted, pole of relay connects to NO terminal. Hence, NC (Normally connected) terminal does not get power and that switches the D1- LED off.