Automatic lighting switch. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Lighting
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In everyday life, it is sometimes necessary that after pressing the switch, the light in the room would be on for a few more seconds. A diagram of such a device was found in a brochure published by one of the Moscow publishing houses almost two decades ago. I slightly modified the machine (see figure) by introducing a variable resistor R4 into it and adding a switch SA1, the role of which can be played by the main light switch.
When the contacts of both switches are closed, the lighting lamp EL1 is on, since the trinistor is open and the diagonal of the bridge on the diodes VD1 - VD4 is closed. When the contacts of the SA2 switch are opened, the automatic delay is activated. Now the current through the control electrode of the trinistor will flow due to the charging of the capacitor C1. But as soon as the capacitor is charged, the current through the control electrode will stop, the trinistor will close, the lamp will go out.
The duration of the delay depends on the capacitance of the capacitor and the set resistance of the variable resistor, it can be from tens of seconds to several minutes. If the delay is not needed, the light is extinguished by switch SA1.
Instead of a variable resistor, it is permissible to use a tuning resistor. Capacitor - K50-27, K50-29 with a capacity of 20-25 microfarads for a voltage not lower than that indicated in the diagram. Trinistor - KU202 or KU201 series, allowing a forward voltage of at least 300 V. All diodes must be rated for a rectified current of at least 300 mA and a reverse voltage of 400 V or more. With a lighting lamp with a power higher than 60 W, you need to set the bridge diodes to the appropriate rectified current.
Switches SA1 and SA2 are conventional electrical switches used in electrical wiring systems. If the main light switch is used as SA1, the X1 plug is not needed - its conductors are connected to the wiring in the switch box (of course, with a de-energized network!). It is even better to replace the single-gang switch with a two-gang one so that SA1 and SA2 are side by side. Near the switches, a case is placed with the parts of the machine mounted inside. The design should completely exclude the possibility of touching the conductors and parts of the device.
Author: S. Belik, Nazarovo-4, Krasnoyarsk Territory
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