Darkness sensitive switch Schematic Circiuit Diagram

Darkness Sensitive Switch: Automatic Outdoor Lighting Control

Darkness sensitive switch: This circuit design facilitates the automatic activation of outdoor lighting in low-light conditions, operating for a predetermined duration. The system ensures that a new cycle starts only after daylight returns. Utilizing a solid-state relay, the circuit triggers the LED in the relay and powers lamp L1 when transistors T4 and T5 are active. Once either of the transistors deactivates, the lamp turns off.

Operation Based on Light Intensity

The functioning of the darkness-sensitive switch relies on phototransistor T3, which determines the state of transistor T5. When T3 detects darkness, it turns on, interrupting the base current to T5. Consequently, T5 can only be active in low-light conditions. Ensuring the switch operates effectively in response to darkness.

Controlling the Lamp’s Operation:

The base-emitter junction of transistor T2 is also linked in parallel with T3, ensuring that it remains off when there is light. Consequently, this action consistently triggers a reset on IC1, causing all of its counter outputs to be in a low state. Once darkness falls, R7 supplies the base current for T2, turning the transistor on. This allows the counter to tally the pulses generated by its internal oscillator while the lamp is still illuminated. When output Q13 rises after a brief duration, T4 switches off, leading to the deactivation of the LED in the solid-state relay and the subsequent extinction of the lamp. Simultaneously, T1 halts the oscillator, resulting in the prolonged high status of Q13. This state remains in place until daylight reemerges, resetting IC1 and initiating a fresh cycle.

Adjusting the Lamp’s Operating Time:

You can set the duration for which the lamp remains on, ranging from 1 to 5 hours, using P1. The power supply doesn’t necessitate a specialized transformer, as it can be directly derived from the mains. Diodes D1-D5 rectify the mains voltage, and C4 smooths the output. C5 functions as a resistor, so it should possess a working voltage rating of at least 400 V, with 630 V being the preferred option. It is crucial to note that mains voltage is present at various locations in the circuit, underscoring the importance of ensuring adequate insulation for the switch unit.