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Build Your 15-Second Courtesy Light Circuit Today
Description
This circuit is designed to allow a user to extinguish a lamp remotely, offering ample time to settle into bed before the illumination ceases. Users will undoubtedly discover diverse applications for this circuit to satisfy their particular requirements.
Circuit diagram :
Parts :
- R1 = 470R 1/2W
- R2 = 100K
- R3 = 1M5
- R4 = 1K
- C1 = 330nF-400V
- C2 = 100µF-25V
- C3 = 10nF-63V
- C4 = 10µF-25V
- C5 = 10nF-63V
- D1 = 1N4007
- D2 = 1N4007
- D3 = BZX79C10
- D4 = TIC206M
- Q1 = BC557
- IC1 = 7555 or TS555CN CMos Timer IC
- SW1 = SPST Mains suited Switch
Circuit operation:
Owing to its minimal current consumption, the circuit can be powered from a 230Vac mains supply without necessitating a transformer. The supply voltage is reduced to 10Vdc through the reactance of C1, coupled with a two-diode rectifier comprising D1 and D2, alongside a Zener diode D3. IC1 functions as a CMOS 555 timer, configured as a monostable, providing a 15-second on-duration, controlled by R3 and C4. When SW1 is engaged, IC1’s output (pin 3) remains permanently active, driving the Triac D4, which in turn supplies the lamp. Disengaging SW1 initiates the monostable operation, and, after 15 seconds, pin 3 of IC1 transitions to a low state, thus switching off the lamp.
Notes:
- The circuit is permanently wired to the mains supply, yet current draw is negligible.
- Due to the transformerless design, there is no heat generation.
- The delay period can be adjusted by altering the values of R3 and/or C4.
- With C4 set to 10µF, increasing R3 will approximately increase the timing by a ratio of 100K per second. For example, R3 = 1M results in a timing of 10 seconds, while R3 = 1M8 yields a timing of 18 seconds.
- Low Gate-current Triacs are recommended for optimal performance.
- Utilize a well-insulated mains-type switch for SW1.
- Warning! The circuit is connected to 230Vac mains; therefore, certain components within the circuit board are subjected to a hazardous potential. Avoid direct contact with the circuit when it is plugged in and enclose it within a protective plastic casing.