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addhone • Nov 30, 2008

Need Help With flashing LED

Right, this is my first post..
I want to make a flashing LED for my car.
At the moment i have a flashing LED wired to my central locking its got a permanent live when the doors are locked,
so it flashes on then off then on then off in 1 second intervals.
but what i want is more like..
on 1. off 1 2 3. on 1. off 1 2 3. on 1....
so i need a shopping list for maplin and a wiring diagram - a simple one.?!
I'm fairly handy with a soldering iron so i wanna do it on Tripad Board (strip board) i have already got a 12v 3mm red Led and want to use that
Simplest design possible though please 😉
sorry its so badly explained but.. hopefully someone can help?!
Cheers, AddHone.
Van Helsing
Van Helsing • Dec 1, 2008
Hello, Addhone, to make a LED blinking could be a trivial task. But it couldn't indeed, dependind on how trained are you with electronics. The timing you are talking about is named "duty cycle". I advice you to read carefully this:

And this one too

Simple LED flasher circuits

I hope this will help you.

hey u can even acheive blinking function by using resistors n capacitors and adjusting the delay but it will be complex for you if ur a novice,watever you shud go with readymade çircuits
addhone • Dec 1, 2008
Thanks for the replys!
I will read them links in more depth later 'Van Helsing',
Where could I buy ready made circuits to archive what i want?
Cheers, AddHone.
addhone • Dec 3, 2008
Think Iv found what I'm looking for!! 😁

*click* Dummy Alarm Project *click*




  • resistors: 1k, 10k, 680k
  • capacitor: 10µF radial
  • LED: red superbright, 5mm diameter
  • 7555 low power timer IC
  • 8-pin DIL socket for IC
  • stripboard: 8 rows × 16 holes

Could anyone help me convert this to run off a 12v car battery??
I Assume you would need to swap the 1k resistor to a 3k3??
Cheers AddHone.
Van Helsing
Van Helsing • Dec 4, 2008
Hi Addhone this is what I suggested you, and it is suggested on the datasheets.The output of the 555 is capable of driving about 200mA but your led may need a bit less. The aproxymate current is 12V/R. Don't mind the led drop voltage. So, if you LED needs 10mA the correct value for R is 12V/0.01A= 1200Ohm. 2400Ohm if your led needs 5mA. And so on... NE555 will withstand 12V but you may need to adjust the value of the other two resistors or the capacitor to achieve the blinking rate you are looking for.Cheers.

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