Hospital ambulances typically use blue mechanical rotary lights. In this paper, we have replaced the traditional rotating system with a more modern and efficient design. Instead of a mechanical light, 16 ultra-bright blue LEDs are arranged in two segments and four groups, forming a circular pattern. The rotation effect is achieved through a sequential illumination of each segment, creating the illusion of movement without any moving parts.
The circuit diagram is shown in the figure. The +12V terminal is connected to the ambulance battery’s positive pole (12V), GND is connected to the chassis, and the A terminal is linked to the door switch. When the ambulance door is open, the door switch S2 remains open. Once the door is closed, S2 closes via a linkage mechanism. If the power switch S1 is turned on at this point, the flip-flop formed by N1 and N2 outputs a high signal, which activates the oscillator N38. The oscillation frequency is determined by the time constants of C2, R3, and RP. By adjusting RP, the speed of the LED rotation can be controlled.
The oscillating signal is sent to the CP input of the CD4022 octal counter IC2, which generates clock pulses. These pulses cause Y0 to Y3 to output positive pulses in sequence, triggering VT1 to VT4 one after another. As a result, the LEDs (LED1 to LED16) illuminate sequentially. Each group of LEDs is divided into two segments, and both segments light up simultaneously. The lighting order follows a specific pattern:
1. LED1, 2 → LED5, 6 → LED9, 10 → LED13, 14 → LED1, 2...
2. LED3, 4 → LED7, 8 → LED11, 12 → LED15, 16 → LED3, 4...
Once the ambulance stops, opening the door disconnects S2, resetting N1 and N2 to their initial state. This causes the N23 pin to go low, turning off N38 and stopping the oscillation. The blue rotating light then ceases to function. At this point, S1 should be turned off, and the 12V power supply disconnected. To enhance the visual effect, high-quality mirrors can be added around the LED array for better reflection and realism.
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