I know this is not new but i really can't find a circuit that makes an led flash once every 5 secs. I hope somebody can help me out.
Thanks a lot.
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https://electronics.stackexchange.com/questions/51547/simple-energy-efficient-circuit-to-make-single-ir-led-blink – Voltage Spike Sep 20 '17 at 22:36
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If you *really* want to use a 555, you'll probably want to start with a [calculator to find the capacitor/resistor values you need](http://www.ohmslawcalculator.com/555-astable-calculator). That particular circuit gives a minimum of 50% duty cycle. If you want a short flash every 5 seconds, then you could design it for a high duty cycle, and use a transistor to drive the LED *and* invert the signal coming from the 555. It's almost certainly easier and cheaper to do this with a tiny microcontroller than a 555 though. – Jerry Coffin Sep 20 '17 at 23:52
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only one 20mA LED? from what V? – Tony Stewart EE75 Sep 20 '17 at 23:57
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An LM3909 is an 8 pin IC designed for exactly that, flashing LEDs. It operates on 1v to 5v and is very conservative on power usage. The datasheets are easy to find online.
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You can consider using an LDO. The MAQ5280 is an automotive grade LDO that may be worth looking into. – PICyPICyPICy Dec 05 '17 at 19:58
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Search for '555 LED flasher circuit' and go to Images. Tons of schematics. Plus, the 555 datasheet has many application circuits included.
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