Light controlled delay circuit (4)

It uses a battery-powered light-controlled delayed lighting lamp. When there is a sudden power outage or the fuse blows out at night,
the room becomes dark and it is difficult to find matches and candles: Sometimes after turning off the lights at night, I still feel like peeing when I go to bed in the dark. With
this small lamp, it can It lights up automatically for a few seconds, which can bring you great convenience. The characteristics of this circuit are that only when the indoor
light suddenly dims, the small lamp can light up. If the indoor light changes from dark to dark or slowly and naturally darkens, it will
not light up. After the small lamp is delayed and extinguished, the circuit will not light up. Consumes electrical energy.
    Figure LL_, NAND gates I and II
form an integral monostable flip-flop.
Normally the circuit is in a stable state, and
NAND gate II inputs I high level. VT1
-VT3 are all in the cut-off state, and the small
spider E does not light up. When there is a sudden
power outage or lights out at night, the photoresistor
RI. Suddenly the resistance is high, and its upper end
outputs - Ar anti-bump pulse, which is coupled to the
(1. coupling), causing the steady-state flip-flop
to enter the transient state, and the NAND II output is low, and VT! is turned on. Single The transient time of the steady-state trigger is determined by R, .
rj, so the VT1 conduction time is only a fraction of a second, and the instrument returns to the steady state at a fraction of a second. This period of time is
enough to allow the charge to be fully charged, VT2, VT3 is then turned on, and the small lamp E emits electricity. After VT1 is cut off, (j
passes through R. It discharges to the composite tube composed of VT2 and VT3, so that the small lamp continues to shine until (j is discharged and
VT2 and VT3 return to cut-off. The little spider goes out. If the light in the room changes from dark to strong, the upper end of Kl outputs a negative pulse,
which has no effect on the monostable trigger, and the lamp E will not light up. In the same way, if the light inside the room
changes , The resistance value of RI slowly increases, and the positive jump through C, coupling cannot occur. The state of the monostable trigger also changes slightly
, and the small lamp still cannot light up.
    Otherwise, a CD4 can be used for rlI and Ⅱ. 11 For the NAND integrated circuit, the input terminals of the other two/used NAND
gates in the integrated block should be grounded and must not be left floating. Use 6.3V, 0 1A small beads for E. It is best to use 4
sections of No. 5 nickel cadmium for G. Recharge the battery. Then install the entire circuit in the lamp holder of the wall lamp RT. It should extend
out of the lamp holder slightly to let it feel the indoor light, but it should not be directly illuminated by the electric beads E to avoid causing light feedback.