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4017 low frequency Digital clock generator / Oscillator

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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salec6 years ago
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.
mario59 (author)  salec6 years ago
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
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




inverter-oscillator.png
+1, if it'll do the low pulse rate he's after.
jeff-o7 years ago
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.)
555 timer ? You dont' say how stable the clock needs to be.

Steve