In general hospital ambulances, the flashing lights are all using blue mechanical rotary signal lights. This article will replace the mechanical rotary signal lights with blue LEDs. The principle circuit is shown in the figure, in order to obtain a realistic effect. High quality mirrors can be added.
In this paper, 16 ultra-bright blue LEDs are used in 2 segments and 4 groups. A total of 4 groups of LEDs in a circle. Instead of a mechanical rotary signal light, a cyclic component-by-segment illumination is used to produce a rotation effect.
The principle circuit is shown in the figure, in which the +12V terminal is connected to the ambulance battery positive pole (12V), the GND is connected to the iron wire, and the A terminal is connected to the door switch. The door switch S2 is open before the ambulance closes the door. After closing the door. S2 is closed by linkage. At this time, if the power switch S1 is closed, the flip-flop 3 of the N1 and N2 outputs a high level and is sent to the oscillator N38 to be in the working state. The oscillation frequency is determined by the C2, R3, and RP time constants. It is adjusted by the RP to control the speed of rotation of the signal light. The oscillating signal is sent to the CP end of the decoding output octal counter IC2 (CD4022) for clock control signal. Let Y0~Y3 output positive pulses in turn, VT1~VT4 turn on in turn, LED1~LED16 sequentially emit light. A blue rotating aura is formed. Each group of LEDs is divided into two segments, two segments simultaneously emitting light. The order of illumination is:
1. LED1, 2→LED5,6→LED9,10→LED13,14→LED1,2... .
2. LED3, 4 → LED7, 8 → LED11, 12 → LED15, 16 → LED3, 4... . .
After the ambulance stopped. As long as the door is opened, S2 is disconnected again, N1 and N2 are reset to the initial state, the N23 pin is turned to the low level, the N38 pin is closed and the vibration is stopped, and the blue signal light stops rotating. Shut down S1 at this time. Turn off the 12V power supply. In order to get a realistic effect. High quality mirrors can be added.
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