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I'm trying to use a 555 timer to flash a LED but I want to be able to adjust the speed of the flashing Answered

I'm trying to build a simple circuit using a 555 timer chip Ideally a low power one so I can power it off 2 AAs to flash a LED at a variable speed from rapid flashing to once every few seconds.

any help would be appreciated.

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frollardBest Answer (author)2010-02-01

You need to incorporate a potentiometer (variable resistor) where one of the resistors currently is:

"if you choose to use a vairable resistor, you should use R2"

555

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joeAMERICA (author)frollard2010-02-01

Awesome thank you I thought a potentiometer would do the trick but was unaware where t connect it, so to be clear it should connect to PIN 7

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frollard (author)joeAMERICA2010-02-02

Also remember as framistan says; make sure to use a variable pot with a series resistor, so that it has a total value of somewhere like 50k-100k

If you use a 100k all by itself you get 0k to 100k; and that very low resistance will probably mess things up.

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framistan (author)2010-02-01

I have an old book that suggests using a 4.7 Microfarad capacitor for pin 6 to ground.  Then a 100k ohm resistor connects to pin 7to plus battery.  This 100k resistor could be INSTEAD a 50k FIXED resistor (plain resistor) and a 50k VARIABLE resistor in SERIES with each other. The schematic I have uses 5 to 15 volts.  you may have to substitute various resistors to get the kind of blinking you want.  most likely your capacitor will be some value between 1uf and 100uf. 

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