Safe and energy-saving button bedside lamp circuit

A delay-type bedside lamp is very convenient for many readers to use at night. The push-button bedside lamp introduced in this article can meet the requirements of safety and convenience. The circuit principle is shown in the figure below. The bedside lamp consists of two parts: a power-saving monostable circuit and a brightness-controllable lighting lamp. The two parts are coupled by a photoelectric coupler, and the electrical part is completely independent, making it very safe to use. When K1 is disconnected, VT1 is cut off, its collector voltage is 0V, VT2 is cut off, and the ground terminal of NE555 pin ① is open circuit and does not work. At this time, the power consumption of the circuit is only the penetration current of VT1 and VT2, about 3~ 5μA, four batteries can be used for more than a year and a half. After pressing K1, VT1 is saturated and conductive, the voltage at both ends of R3 is close to the power supply voltage, VT2 is saturated and conductive, and NE555 works. At this time, the second pin of NE555 changes from high level to low level, and is lower than 1/3 The power supply voltage, NE555 flips, the ③ pin outputs a high level, one of which can drive the photoelectric coupler 4N25 through R7, making the triac VS conductive, and the bedside lamp H lights up; the other one passes through the diode VD1 and the resistor R6. VT2 provides a large enough bias current to maintain VT2 saturated conduction. At this time, even if K1 is disconnected, the working state of VT2 remains unchanged, that is, the temporary stable state of NE555 remains unchanged. During this period, the power supply charges C1 through R5, causing the voltage at both ends of C1 to continuously increase. When the voltage at both ends of C1 is greater than 2/3 of the power supply voltage, the NE555 discharges through the 7th pin of the discharge terminal, and the transient steady state of the NE555 ends. The third pin ③ changes from high level to low level, VT2 is cut off and enters another stable state. Only when K1 is turned on again, NE555 enters the temporary stable state again and the bedside lamp lights up again. The component models and data used in this bedside lamp are as shown in the attached figure, and there are no special requirements. The entire bedside lamp is easy to install and debug. As long as it is installed correctly, it can be used normally. If the delay time is too short, you can increase the resistance of R5 or the capacity of C1, and vice versa. During installation, the buttons are placed externally and the remaining components are placed in a plastic box to ensure safe use.