# how to generate a 1hz clock

Discussion in 'Electronic Basics' started by Yaron, Oct 14, 2003.

1. ### YaronGuest

I just wanted to know how
can I generate a precise 1 hertz clock pulse.

2. ### Anthony FremontGuest

It all depends upon your definition of precise. You need to state some
limits like accuracy, cost, size, power requirements etc. If you need
an extremely "precise" 1hz clock, use a GPS receiver. If "wall clock"
accuracy is your goal use a crystal based oscillator or maybe hack a
cheap quartz clock module. If you're cooking eggs, use a RC based
circuit like 555 timer. ;-)

michael

3. ### Don BruderGuest

Use a 74HCU04, two caps, two resistors, and a known-value crystal.
(Somebdy please refresh my memory on the name for this type of
oscillator? I think it starts with "F", but I'm not sure.)

Feed the output to circuitry that behaves as a "divide by <crystal
frequency> counter", and take your 1 Hz signal off of the output from
that. You may want to feed it to a schmidtt trigger to be sure it's nice
and clean before actually putting it to work, but I'd consider that an
optional improvement. Presto. Crystal accurate 1 Hz oscillator

4. ### Costas VlachosGuest

You can use a 32.768 kHz crystal oscillator, and then divide that frequency
using a 15-bit binary counter. The crystal's frequency value is a power of
2, so the division will be perfect and you'll end up with an accurate and
precise 1 Hz square wave. The crystal is cheap and easy to find, as it is
commonly used in digital watches.

Or, you could use a small microcontroller (with a crystal oscillator) and
generate the pulse with code. This could well be the easiest solution (only
one IC required), depending on how familiar you are with MCUs.

http://ourworld.compuserve.com/homepages/Bill_Bowden/page11.htm#counter.gif

HTH

Costas

5. ### John LarkinGuest

Buy a cheap mechanical-dial quartz clock and tap into the stepper
motor drive pulses.

John

7. ### Bill BowdenGuest

There is digital clock circuit with a 1 Hz generator at :

http://ourworld.compuserve.com/homepages/Bill_Bowden/dclock.htm

It uses a 32768 Hz watch crystal and a 4020, 14 stage counter
to get 2 Hz. The 2 hertz signal is divided by 2 to get a
1 Hz square wave out of the 4013 flip flop.

There is also another clock circuit that divides the 60 Hz line
frequency down to 1 Hz. but you need almost as many parts either
way.

-Bill