4017 Decade counter

[vick5821]

The cap/resistor forces a single reset with every power up, without this forced reset the counter will not always start at 'zero', you will instead (may) get odd behavior with each power up and a random counting start point...

How it does that ? I want to know.

Thank you

 

[CocaCola]

Do you understand how capacitors work? They will pass DC current until they are charged and then stop...

So upon power up the cap will for a brief time bring pin 15 high as it passes the supply current to the pin, but once it's charged it will block that current to the pin and the 22K will pull the pin back to ground, the resistor also dictates how fast the cap will charge so you can control the duration of the reset in this case...

 

[vick5821]

Cant see much difference if I change thee resistance value

Is this seems to be a positive edge trigger phenomena ? But it look to me is like a negative edge triggered as the next LED lights up when the blue LED LOW

So ?

 

[CocaCola]

Cant see much difference if I change thee resistance value

What resistor value? The reset on power up it just a single shot thing there is nothing to see...

Is this seems to be a positive edge trigger phenomena ? But it look to me is like a negative edge triggered as the next LED lights up when the blue LED LOW

So ?

So.... Read the datasheet... http://www.doctronics.co.uk/pdf_files/HEF4017B.pdf

"The counter is advanced by either a LOW-to-HIGH transition at CP0 while CP1 is LOW or
a HIGH-to-LOW transition at CP1 while CP0 is HIGH"

 

[vick5821]

You mean pin 13 as clock input for negative edged triggered ?

 

[CocaCola]

You mean pin 13 as clock input for negative edged triggered ?

The counter is advanced by either a LOW-to-HIGH transition at CP0 (Pin 14) while CP1 (Pin 13) is LOW or a HIGH-to-LOW transition at CP1 (Pin 13) while CP0 (Pin 14) is HIGH

 

[vick5821]

Well, ok. I see the difference between this two already. But based on the output, I do not know how does it seems to be positive edge triggered. When the blue LED (refer to video) flash(From HIGH to LOW), it will cause the subsequent LED to light up. Is this a positive or negative triggered then ?

 

[CocaCola]

It's positive triggered, either on the rising or falling edge depending on your configuration...

 

[vick5821]

positive triggered means it is rising isnt that ? Positive triggered means the LED will lights up when the clock make transisition from LOW to HIGH