Circuit is a simple light switch without hysteresis (because of that is not the most appropriate switch for soft light transition). For light switch, we have used operational amplifier LM741 in comparator orientation. Comparator compare voltage levels on his inputs. At pin 2 is connected resistor divider with light sensitive resistor (LDR). The voltage changes with changing light on LDR. On pin 3 is connected reference voltage provided with resistor divider with one fixed value resistor and with one potentiometer (trimmer). With trimmer, we can set light switch sensitivity. When the voltage on pin 3 higher than voltage on pin 2 is operational amplifier output (pin 6) in high level (mean that is supply voltage on output). If we have opposite situation the output is in low level (ground or 0 V).
How it works
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