Elektor Team
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Led Flasher

Led Flasher
A flashing LED based on a 555 is not likely to win the first prize for originality, but such a circuit continues to be useful for all kinds of applications. The thing that makes this version special is the very low current consumption, because the LED flashes only very briefly each time (dutycycle of only 10%) and because it was specifically designed to serve as a (fake) alarm indicator in a car. The circuit has been configured such that the flashing only starts when the ignition is switched off.The latter could have been achieved in the usual way with the aid of two resistors and a transistor connected to the reset line. But by using a clever trick instead, this has become even simpler.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Component list
R1 = 470kOhm
R2 = 1MOhm
C1 = 100nF
C2 = 220nF
D1 = LED
D2,D3 = 1N4149
IC1 = 555
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