A delay-type bedside lamps, for many readers to use at night is very convenient. This article describes the touch-safe and convenient bedside lamp requirements of circuit as shown below.

The bedside lamp from the power-saving single-shot and brightness of the controlled lighting of two parts. Of two parts coupled by optical coupler, electrical parts of complete independence is very safe to use. When K1 is off, VT1 off, its collector voltage is 0V, VT2 end, NE555 first open ground without foot work, this time, the circuit power consumption is only VT1, VT2 penetration current, about 3 ~ 5µA, four batteries can use more than one and a half. After pressing the K1, VT1 saturated conduction, R3 both ends of the voltage approaches the supply voltage, VT2 saturated conduction, NE555 work, this time, NE555 first ? feet from the high to low, and less than 1 / 3 supply voltage, NE555 flip, the first pin output high, its all the way through R7 can drive optocouplers 4N25, turn the triac VS, bedside lamps lit H; the other way through the diode VD1, resistor R6 large enough to provide bias VT2, VT2 saturated conduction to maintain, at this time, even if the K1 off, VT2's work status is unchanged, that steady state of constant suspense NE555. During this period, the power charge through R5 is C1, so that the rising voltage across C1 when the voltage across C1 is greater than 2 / 3 of the power supply voltage, the discharge through the end of the first NE555 foot discharge, NE555 end of the temporary state The third feet from the high to low, VT2 end, to another stable state, only when connected again in the K1, NE555 only re-enter the temporary state, bedside light up again.
  The bedside lamp model and data used in components such as the photo shows, no special requirements. The bedside lamp easy to install, easy adjustment, as long as the installation is correct, you can normally use. If the delay time is too short, can increase the resistance of R5 or C1 capacity, and vice versa. Key part of the external installation when the remaining components into the plastic box to ensure safe use.