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Resistors and Capacitors

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mettam

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I have learnt that a capacitor charges and discharges over time so with that in mind is it possable to run a 9Volts through a capacitor and have a LED flash on and off.
Or maybe a I would need to use both a resistor and a capacitor.
I did it with a 555IC but it seems it should be achievable just with just a R and C.

I hope this question isn't to basic for this forum..

Justin.
 
When put together with a resistor or LED, a capacitor will indeed charge OR discharge over time, but will not charge AND discharge over time. So it will charge up to 9 volts only once and then stay there. At the very beginning of this when you first apply the voltage, the LED might light a tiny bit and very briefly but only that once and nevermore. There will be no flashing unless you add additional stuff (like the 555) to do some additional switching.
 
The 555 timer takes the ramp signal from an RC circuit and converts it to a square wave signal. The signal goes from 0 to VCC, if the signal is slow enough (less than 30 Hz) you can see the LED blinking.

However, if you want to use the ramp signal, it will give the LED a Fading in and out apperance. See this circuit for more info
**broken link removed**

I myself have used that circut and it is visually Appealing.

(the above needs grammer checking, its 3:30AM in the morn.. But you get the idea)
 
Just get a flashing LED, it will work right off 9 volts with no other parts required. The flashing circuitry is built into the LED.
 
Radio Shacks flashing LEDs requires 2.5 - 5v, typical 3v. Have not tried them at 9v, seems a little high for the specification.
 
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I didn't consider the Radio Shack ones. The ones I use are from Mouser Electronics and they have a typical operating voltage of 3V min and 14 volts Max. The forward voltage affects the fash rate.
 
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