Light controlled delay circuit (2)

It is used in the bedside wall lamp circuit. When you turn off the lights at night and go to bed, it can automatically light up about imin, which can
bring warmth to your bedroom and make your life more convenient.
    220V AC power is rectified by VD2
, f. Filtering, R, and R. By dividing the voltage,
about 10-15V DC
voltage is obtained at both ends of R. Normally, VT1 is in the cut-off
state, the gate of thyristor VT2 is extremely low
, VT2 is turned off, and the wall lamp F is on
. When L turns off and prepares to sleep at night, the indoor
light suddenly dims, and the value of the photoresistor
RLm increases (1: the left end ￡乜 position rises
, so the electric pressure passes through R,, c,, R,,
VT1 emitter junction and When there is a gram of electric current, VT1 is turned on by the forward bias current, and the emitter outputs m
high level , so the VT2 f J pole is turned on by receiving the F-direction trigger current, and the lamp E lights up. When f. charge After being fully charged
, VT1 loses its "F-direction bias current recovery cutoff", vT2 gate has no trigger current, turns off when the AC crosses zero , and the lamp F goes out. For example, when the indoor light becomes stronger, the resistance value
of RI becomes smaller. C, the potential at the left end decreases. At this time (1), the stored charge will be discharged through RI_. VD1 can be used to prepare for charging when the lights are     turned off at night. R, VT1 can be placed in the reverse biased state at ordinary times to ensure that VT1 is cut off reliably. In C ．During the charging process, R acts as a bypass, so adjusting the R resistance can control the time that the light E lights up each time after turning off the light. The larger the R resistance , the longer the delay time, and vice versa. Using the graphic data, the delay time is about imiri. But R cannot be omitted , otherwise when the VT1 tube is of poor quality and the penetration current is too large, VT2 will always be on and the light F will not turn off. .     This circuit is mainly used for auxiliary weak lighting after turning off the lights. The lamp E should use a 5~15W low-power incandescent bulb. When VT2 is turned on, half-wave alternating current flows through E, so the light color is soft and dim, which can add Indoor fun. VT1 uses 901 type 3 silicon tube with a p value of about 10; VT2 officially uses BT169, 2N650., MCR]00 type 8 and other one-way thyristors with small trigger current. (,: CBB-4 is required. 0V type polypropylene capacitor. No special requirements for other components.