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How can I make a LED blink on and off? Answered

I just ordered some 3mm leds, and I would like to know more about them. One thing is how to make it blink on and off. If someone could help me that would be great.

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The absolutely simplest way is to buy a blinking LED. These have the flashing circuitry built in.

Any electronics store, either high-street or on-line (Maplin, Mouser etc) or they're dirt-cheap on eBay.

That link I gave you was rubbish - mainly quantities of 1000 and from far east. Try THIS.

us an lm3909, you can find them on futurlec.com for cheap

simple enough to use a 555 timer set to astable mode (it runs as a clock) to drive the LED.

See http://www.national.com/ds/LM/LM555.pdf page 7 under "Astable Operation" for a circuit that requires
1 555 timer, 2 resistors, and two capacitors, plus, of course, the LED and its current limit resistor) (it would be the lower "Rload" between pin 3 and ground in figure 4 of the cited document)...

very easy.

But I do agree with the "blinking LED comment below mine

Depending on how complex you want to go:

1. Buy a flashing LEd they are cheap.
2. Go down the microprocessor route and have many more options. try http://www.picaxe.com lots of information there - Forum is good too.