urban road construction at night is usually set at the construction site and opened the red warning lights to prevent night staff, vehicle accidents in the past. In order to improve the effect of warning, energy-saving and easy to use, caution light work best in blinking, and automatic control. This article describes the warning lamp control circuit with the Flash and light two features, that can control the lights automatically turn on after dark and to work in Flash, and warning light automatically shut down after dawn. Working principle of warning lamp control circuit as shown in Figure 1. A NPN-transistor VT1-VT2 and a PNP transistor-complementary ultra-low frequency of a frequency adjustable oscillator whose oscillation frequency can be adjusted by the RP1. VT2 base and power supply has a photosensitive resistor between the negative side, constitute the ambient light detection circuit to achieve photoelectric control. VT1 thread with R2 in the collector loop current-limiting resistor, its control work with photoelectric coupling of bi-directional thyristor chips IC1, IC1 control conduction and cutoff in driving high power two-way Silicon control SCR, SCR directly controls the warning lamp lights, fight. C1, VD1, VD2 components form a typical capacitance of buck power supply circuit, control circuit as a whole provided 5 v DC power supply. When the day, due to the ambient light light, RG is light, the resistance smaller, VT2 base voltage constant at low potentials, so made up of VT1 and VT2 complementary ultra-low frequency oscillator stop vibrating. VT1 and VT2 is due at this time, slip extremely low potential for VT1, IC1 is not working, SCR closed warning light is not lit, the entire circuit at rest. After dark, RG resistance due to light exposure and larger (about 1M ω), lose control to VT2 base, therefore, made up of VT1 and VT2 complementary ultra-low frequency oscillators to starting work, VT1 occurs periodically the beginning collector output potential of high and low variations. When you output it as a high potential, IC1 triggered and driven SCR conduction, the outlet of Chinese and foreign light lit when when its output is low, IC1 and then stopped working, SCR restoring close warning light goes off.  
This warning light lit out on ultra-low frequency oscillator controlled by cycle works in Flash. Component selection circuit used in component specification parameters are marked in Figure 1. IC1 selection MOC3041 zero-crossing trigger photoelectric coupling two-chip silicon chips. C1 and SCR voltage should be ≥ power required for Visual control of the 400V,SCR total power depends on the size of the warning lights. VD1 selection voltage values are 5V Zener diodes. Standard diode type VD2 1N4001 selection. Selection models for 3CK3C-PNP transistor VT1; selection model for 3DG6 NPN-transistor VT2, requiring VT1 and VT2 β ≥ 60. ≥ 1M ω RG selection dark resistance, light resistance ≤ 10K ω of photosensitive resistor. RP1 selecting small horizontal solid core potentiometer, so that it can be welded directly on a printed circuit board. R3, R4 Power 1W resistor should be used. Remaining components are universal, no special requirements, can be shown in the standard specifications flexible choice. Single-sided printed circuit board of the circuit diagram shown in Figure 2. For the shell you can use the appropriate size of wood or plastic casing, in the light and photosensitive resistance on the Panel face parts correspond to note to leave a loophole so that the control circuit to work properly.

Output socket on the rear panel that can be installed directly in the case. Adjustment method: on the circuit while debugging, start using the smooth black blanket cover RG, to simulate the night-time light-free status. At this point, the ultra low frequency oscillator should be capable of starting work, warning lights should blink, the flicker frequency should be regulated through RP1, shows warning lights flashing control circuit is working properly. Then, black blanket removal screened RG, at this point, the ultra low frequency vibration oscillator should be stopped, warning lights, description control circuit also works fine. The entire circuit can be put into normal use. Actual trial proves that the circuit stable, reliable performance, convenient installation and debugging, more suitable as a warning lamp control circuit used in road construction in cities and towns.