Please help with simple circuit

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h22221

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Hi All,

Right, I am trying to make a very small simple circuit that makes an LED illuminate for 5 seconds when power supply is turned on, then after 5 seconds the LED should extinguish and remain off until power is switched off and then switched back on at which point it lights again for 5 seconds.

I want to make it as simple, cheap and as small as possible, it is being fed off a car stereo ATT wire so 12v I think when ignition is switched on.

Thanks for any advice
 


R2 sets the current through the LED

when turned on, C1 will charge through R1 when the voltage is > 0.6V the transistor turns on and bypasses the LED and the LED turns off

if R1 is 220k, then C1 would be 470uF
 
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    h22221

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For a simple circuit, I guess you have to use the famous 555 timer IC. Its very cheap and are available everywhere. I think you will find it in you place. The IC have to be used as a monostable, that is, a trigger will start a pulse for the time you need and will shut down until next trigger is initiated or the circuit is restart. You need few more passive components. Here is something I draw...





P.s: R1 & C2 will be 2.2MΩ & 2.2uF respectively...
 
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Thanks for the answers, I think the 1st suggestion would be the simplest as 555 thingy looks quite complex and I really do want this as simple as possible.
Do you have a list of components I would need please? I want to use the smallest LED possible, so unsure if that makes a difference?

Thanks again
 

The transistor circuit may have to be changed like this to work properly.
 

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