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4017 low frequency Digital clock generator / Oscillator Answered

Hi to all!
I need to "feed" a digital clock pulses to a CD4017 decade counter. It should be possibly with only 1 active component and very, VERY few passives components around.
It should give 1 to 30 pulse/second rate. FIxed frequency oscillator.
It needs to be simplest, for the space constraints I have.
Do anybody knows if it is possible? ;-) 

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salecBest Answer (author)2010-06-09

smallest single component that produces slow (few Hz) pulses I can think of would be a flashing (blinking) LED, if you have source for them. I guess you could bias it over a resistor (not needed when used for intended purpose of ... blinking), to generate voltage pulses for 4017 clock input.

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mario59 (author)salec2010-06-17

Ciao Salec! Thanks for your kind response. The idea of a blinking led is VERY VERY good, but with only one miss: the pulse rate is fixed- But you really get it: 99.9999% !!!. I could never say enything else! thanks again ciao Mario

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Jack A Lopez (author)2010-06-01

I know everyone loves the 555,  buy why not build this oscillator out of CMOS inverters instead?  I mean if you're already using a CD4017, why not use another chip from the same family, like a CD4049 hex inverter. The oscillator circuit only requires 3, or maybe 2, of the 6 inverters on the IC, plus one capacitor and two resistors.

The attached picture is from this document:
http://www.fairchildsemi.com/an/AN/AN-118.pdf
and it gives all the gritty detail you could possibly want about this kind of oscillator.

Also, the data sheet for those inverters, from alldatasheet.com:
http://pdf1.alldatasheet.com/datasheet-pdf/view/8178/NSC/CD4049.html




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user

+1, if it'll do the low pulse rate he's after.

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jeff-o (author)2010-06-01

A 555 timer would do the trick, but if you really want to eliminate as many passives as possible then you may want to look into using an 8-pin microcontroller.  Overkill?  Probably.  But it'll be more accurate than a 555 timer, more versatile and will use only one external component (a pull up resistor on the reset pin.)

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steveastrouk (author)2010-06-01

555 timer ? You dont' say how stable the clock needs to be.

Steve

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