Photoelectric switch
The circuit utilizes a Cadmium Sulfide (CDS) photoresistor, which is a light-dependent resistor that changes its resistance based on the intensity of light it receives. In low light conditions, the resistance of the CDS cell is high, preventing current flow. As light intensity increases, the resistance drops, allowing current to pass through the circuit.
The 2N3904 is a popular NPN transistor used as a relay driver in this configuration. When the CDS cell's resistance decreases sufficiently due to light exposure, it allows a voltage signal to reach the base of the 2N3904. This turns the transistor on, enabling it to conduct current from its collector to its emitter, thus energizing the relay connected to the circuit. The relay can then be used to control larger loads or devices, effectively acting as a switch that is activated by ambient light levels.
The simplicity of this circuit means that it can be implemented without the need for a circuit board, making it suitable for compact applications or prototyping. The components can be easily connected using jumper wires or a breadboard, allowing for quick adjustments and testing in various light conditions. This circuit is particularly useful in applications such as automatic lighting systems, where the activation of lights is dependent on the surrounding light levels.The CDS cell resistance decreases in the presence of light, turning on the 2N3904 relay driver. You do not need even circuit board for such a small circuit. 🔗 External reference
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