LCD-LED DisplayLights and Display Board Circuits

Put that Light Out! Schematic Circuit Diagram

Forgetting to turn off lights in infrequently used spaces, like an attic, often leads to them staying illuminated for months, significantly increasing your electricity costs. How can we avoid this wastefulness? It’s quite feasible for electronics enthusiasts to create a small circuit that addresses this absentmindedness. The concept is straightforward: if the light is left on when the hatch or door is closed, a periodic sounder or buzzer generates an alarm, ideally not drowned out by other noises. The circuit remains active as long as the lamp bulb is switched on via the light switch S1.

Put that Light Out! Schematic Circuit Diagram

Hatch Closure Detection and Signaling

When the reed switch S2 detects the closure of the hatch, the sounder activates, alerting about the hatch being closed. Simultaneously, a red LED placed outside the loft adjacent to the entry hatch illuminates, indicating that the loft lamp needs to be turned off. To maintain safety, the circuit operates without a transformer, requiring all components to be enclosed within an insulated plastic case. This ensures that no part of the circuit, including the sounder, is accessible to individuals. Even the connecting wires to the LED and reed switch contact must be meticulously protected to maintain touch-proof safety standards.

Operating the Sounder and Voltage Limitation

A direct current sounder operating within the range of 1 V to 3 V can be used in this setup. The circuit’s operating voltage is limited by the parallel connection of the LED to the buzzer. Utilizing a red LED results in approximately 1.7 V supplied to the sounder. These miniature sounders typically require about 5 mA of current. Proper selection of components ensures both functionality and safety.

Role and Functionality of Transformers

Transformers play a vital role in electrical energy transmission, converting AC voltage without altering the frequency between circuits. Using the principle of electromagnetic induction, transformers transfer energy from one electric circuit to another. They can either increase or decrease AC voltage while maintaining the current frequency. This inherent functionality facilitates efficient power transmission and distribution in electrical systems.


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