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555 Flashing LED

Grex

May 24, 2012
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May 24, 2012
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Whats up guys,

So I hooked up an LED with a 555 timer and am trying to get the LED flashing.

http://www.555-timer-circuits.com/flashing-led.html

I built the circuit based off the schematic shown in the link above, but my LED will turn on and remain on. I'm using 9v power supply and a 47 micro-farad capacitor instead of the 1micro-farad cap he recommends using. If anyone has any idea as to why this is happening hit me back.

Thanks,
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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Do you have the 555 around the right way?

have you connected everything up correctly?

Do you have the correct value components?

These are the three common mistakes.
 

Grex

May 24, 2012
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555 is in right way. Pin 2-6 & 4-8 connected... Values of components should be ok. I found that I didn't have pin 1 connected to ground now that its grounded, the light doesnt come on at all. Now I'm really confused haha
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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I don't see the capacitor.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Yeah, you should be able to get away without that other capacitor.

Is it possible you have the capacitor around the wrong way (or have had)? It looks like a tantalum and connecting it backwards can increase the leakage current dramatically (and permanently). If you can measure the resistance of this capacitor and it stabilises at 2M or more then you're probably safe. Alternatively, try another capacitor.
 

Grex

May 24, 2012
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Yeah, you should be able to get away without that other capacitor.

Is it possible you have the capacitor around the wrong way (or have had)? It looks like a tantalum and connecting it backwards can increase the leakage current dramatically (and permanently). If you can measure the resistance of this capacitor and it stabilises at 2M or more then you're probably safe. Alternatively, try another capacitor.
Forgot the tantalum's were polarized ... I flipped the cap now the light comes on an stays on. I don't have a multimeter on me to measure the cap though, unfortunately.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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It is possible that the leakage is high enough that the capacitor never charges.

I presume you've left it powered for 30 seconds or more? The time constant is around 15 seconds for these values, but the first time its powered up the initial delay could be 50% or so longer.

If you have another capacitor, try that. or try reducing the value of the 470k resistor.
 

Grex

May 24, 2012
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Alright, I managed to find a 1micro farad electrolytic cap... I put it in and still no luck. Also tried switching to lower resistance but no go...
 

CocaCola

Apr 7, 2012
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Jiggle all the wires and twist the chip a bit... I hate stab lock boards and have wasted a great deal of time banging my head due to poor connections over the years when using them...
 
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