Flashing timer

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#1
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Hi all

I need to build a simple flashing led circuit. What needs to happen is that when it is powered up the LED flashes for 10 seconds then turns off but the power will still be on the circuit.

I can work out how to build the circuit to creat a flashing LED or a circuit to have a 10 second delay but not sure how to conbine them into one circuit.

All help really appreciated.

Cheers

Craig

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A little 8-pin AVR could do this with nothing else but the LED and resistor, and maybe a dozen lines of code. If you want to do it using only hardware you're looking at an astable multivibrator (the flashing part) enabled by a monostable multivibrator (the on-for-10-seconds part).

Mike

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Thanks very much for that, i just thought a micro might be an over kill but if thats all the hardware needed it would be a lot easier.

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The one other issue is your power supply. The AVR supply voltage range is smaller than if you were to use a hardware-only approach. Depending on the voltage you have available you may need to add a little regulator as well. Just something to keep in mind.

Mike

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it is going on to a car so i will need to put a regulator on the circuit.

The whole circuit wouldn't draw anymore than 100mA would it?

The micro will draw very little and the LED would be around 20mA.

Craig

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cwilson wrote:
it is going on to a car so i will need to put a regulator on the circuit.

The whole circuit wouldn't draw anymore than 100mA would it?

The micro will draw very little and the LED would be around 20mA.

Craig


Right, the uC might draw a mA, give or take. Obviously you don't need to clock it very fast.

And of course, once you're using a uC you can get playful, speeding up the blink as the OFF time approaches, or whatever tickles your fancy.

Mike

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Thanks Mike

Have a program already running on my STK500. That was nice and easy.

I think a Tiny13 would be perfect for the job and has plenty of room to play with the code too.

cheers

Craig