How can I divide the frequency

Thread Starter

peterlan

Joined Sep 13, 2008
5
Hello everybody, I am doing a project on building a digital clock. Now I have the crystal oscillator 4Mhz already. I would like to know how to divide the frequency to 1 hz since the clock of the digital clock need to be 1 Hz. Anyone who has some idea plz tell me?
PS. I have found some IC's that can divide the frequency ;74HC390 which can divide up to 100 but i still dont know how it work.Moreover I've found some circuit like this
http://www.elecfree.com/electronic/xtal-oscillator-frequency-by-74ls04/ .


Thank you in advance
Pete
 

hgmjr

Joined Jan 28, 2005
9,027
Ordinarily, if you don't intend to achieve a resolution below 1 second, you would start with a much lower frequency oscillator. 32,768 Hertz seems to be a popular starting frequency. The crystals that are available at this frequency abound. The nice part about starting with this frequency since it is equal to 2 raised to the seventh power is that it is easily divided down using a commonly available counter IC.

hgmjr
 

hgmjr

Joined Jan 28, 2005
9,027
You can use a DS1307 but then you would need a microcontroller to set it up using the I2C interface.

I got the impression from your initial post in this thread that you were looking for a non-microcontroller based digital clock design.

hgmjr
 

nanovate

Joined May 7, 2007
666
I got the impression from your initial post in this thread that you were looking for a non-microcontroller based digital clock design.
If the OP can use a microcontroller then the division would be a simple programming task.
 

SgtWookie

Joined Jul 17, 2007
22,230
I agree, a microcontroller would be the way to go.

However, if the OP insists on using a 4MHz frequency source, the attached divider circuit would get them down to 1kHz, or 1/1000 of a second clock increments. Adding another pair of 4518 stages would get them down to 1/10 second.

If they're using a crystal, the AND gate could be replaced with a 4093 quad Schmitt-trigger NAND; use two as the crystal driver & buffer, and two to build the functionality of the AND gate.
 

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hgmjr

Joined Jan 28, 2005
9,027
I too agree that a microcontroller would be the way to go.

The added flexibility and additional functionality could prove very valuable in the end.

hgmjr
 

Thread Starter

peterlan

Joined Sep 13, 2008
5
thx verymuch for every body for any suggestion. Actually,I also want to use the microcontroller but I don't have the knowledge on that much and I think I have only one week to do this project. However, i really thanks for every suggestion .

Ah I have a question Depend on this
"the attached divider circuit would get them down to 1kHz, or 1/1000 of a second clock increments. Adding another pair of 4518 stages would get them down to 1/10 second.

If they're using a crystal, the AND gate could be replaced with a 4093 quad Schmitt-trigger NAND; use two as the crystal driver & buffer, and two to build the functionality of the AND gate."

If I do according to the attached i'll get the clock as 1/10 second , I need to divide by 10 another time right? Or not?
 

hgmjr

Joined Jan 28, 2005
9,027
Since your target frequency is 1 Hertz you will need the additional dividers to get there.

If your interest is inclined toward microcontrollers, I would suggest that you make a commitment to become familiar with the subject as soon as it is convenient for you to do so.

hgmjr
 
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