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Bluish Flasher(1N4148)

2017-02-04 20:19  
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This article briefly describes Bluish Flasher (1N4148). This principle is easy to understand, but also very practical. Depth understanding of circuit elements, you can better grasp this principle. In this circuit, you can learn about and purchase these components: 1N4148.

Firstly, it demonstrates how the combination of a blue and a whiteLEDcan be used to give a realistic imitation of a camera flashlight. Secondly, the good old 555 IC is used in a way many of you may never have seen before alternately mono-stable / astable without too much in the way of external parts. Initially C3 will be empty, pulling output pin 3 to 12 V and causing the blueLED, D1, to light via R3. Next, C3 will charge up via R2. Meanwhile C1 has been building up charge through R1 and D3. If the voltage on C3 reaches about 8 V (two-thirds of 12 V), pin 3 of the 555 will drop Low. So does pin 7, causing the whiteLEDto light, pulling its energy from C1. This energy drops quickly, causing D2 to dim in an exponentially decaying fashion, just like a camera flashlight.

Figure:1 Bluish Flasher Circuit Diagram

Figure 1 Bluish Flasher Circuit Diagram

Now, because the 555’s output has dropped Low, the voltage on C3 will decrease as well. Ad soon as a level of 4 V is reached (one third of 12 V), the above cycle is repeated. Resistor R4 limits the current through the 555 to safe levels. You may want to experiment with the latest hyper-bright whiteLEDs. SDK’s AlInGaPLEDs, for example, are claimed to light three times as brightly as regular whiteLEDs. A number of blueLEDs may be connected in series instead of just one as shown in the circuit diagram. Unfortunately, that is not possible at the ‘white’ side. For the best visual effect, the white blueLEDs should be mounted close together. When fitted close to the extra brake light in your car, the bluish white flash is sure to make even persistent tailgaters back off. Note however that this use of the circuit may not be legal in all countries.



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