Roadblock flashing warning light circuit (4)

It is a battery-powered roadblock flashing warning light that can be
installed on local roads with AC power supply for roadblock warning purposes. hF555 and RP1, RP2, (., RI. form a light-controlled self-excited multivibrator . During the day, RJ is exposed to light and shows low resistance. NF: The level
of the ④ pin of the forced reset terminal of 555 is less than 0 4V. NF.J55 The ③ pin of the forced reset output terminal is always low level. Vll and wT2 are cut off, and the alarm light E lights up. At night RI, when there is no light, the resistance is high, and the voltage of 4 and RP2 makes the level of pin ④ rise. When the circuit is at 0 tv , the blockage on the circuit is released and the circuit starts to oscillate.     Principle: The ② pin of NE5 5 5 is low level. At this time, the circuit is set, ③ pin outputs high level , and ③ pin Through RP1 to C, the photoelectric, so that (,, the voltage at the bend terminal, that is, the level of pin ⑥ is constant). When it rises to 2,73 of the power supply voltage , the circuit breaker resets, pin ③ outputs low level, then c, Discharge to pin ③ through RP1 , causing the voltage at terminal C, that is, the level of pin ②, to continuously decrease. When it drops to 1/3 of the power supply voltage , the circuit cross is set to 䗗, and pin ③ suddenly changes to high fU level, and the cross passes through RP1 Charge to L... and it will oscillate over and over again . Therefore, the gap between pin ③ outputs high level and low level. When pin ③ outputs high level, VT1 and VT2 are turned on, and E is lit; when pin ③ outputs high level, When the input is low , VT1 and VT2 are cut off, and F is extinguished. It can be seen that as the oscillation of the time circuit NE555 proceeds, the warning light E will continue to flash and glow. The frequency of the flashing can be changed by RPl. , adjust the light control sensitivity of RP2 to strip the whole circuit so that the circuit can operate normally under appropriate illumination .     R1. Can be H1 MC, 45 type and other photoresistors. VT2 requires the use of NPN type high-power two-tube tubes. .R uses automotive 12V light bulbs, and a red lampshade needs to be installed on the outside. G is a 12V battery. Other components have no special requirements.