1hz clock

KE7GKP:

Line frequency is not that accurate

For the purposes of long-term time accuracy, power mains frequency is just as accurate as the NITS Atomic Clock. Because all the utility companies maintain the grid frequency against WWV.

Yeah that 'NITS' atomic clock isn't all it's hyped up to be :wink:

To satisfy my curiosity (which you're obviously under no obligation to do...), can you point to something that documents this? Oh wait, here it is: Utility frequency - Wikipedia

If you have a 12 bit counter, why not go all the way to 15?
http://focus.ti.com/lit/ds/scls704a/scls704a.pdf

Digikey (where I'm buying from) only sells minimum 880. How about a cheaper 14-bit unit with a toggle (2-bit) connected to the output? 2^14*2 = 32.768kHz.

tastewar:
Yeah that 'NITS' atomic clock isn't all it's hyped up to be :wink:

The Knights of NI have a Time Service?

What is the average hz of an unladen swallow's wingbeat? :grin:

But eight dual flip flops would be 16 flip flops total... 2^16 = 65536. I'm looking for 2^15. If I use seven dual flip flops, what should I use to take the frequency from 2hz to 1hz?

Doh! :stuck_out_tongue:

I just hit my self in the head b/c I realized I am being WAY to harsh on myself. I'll just use a 65.536kHz crystal and use a dual 8-bit (16 bits total) binary counter to bring it down to 1 hz.

Thanks for all the help!

OK. So I found the 74HC590. This is an 8-bit counter, right? So if I daisy-chain 2 of these, I should get the 65.536kHz crystal down to 1Hz?

an ATtiny and an external 8 or 16 Mhz crystal could do it (Set it up to pulse every second)

I am going to end this topic and start a new, more specific one. Thanks for all the help!

Yes,
Feed 64 KHz into CCLK, RCO from stage 1 into stage 2, RCO Pulse from will yield a low going pulse 1/64K wide 1x a second.

See figure 3 for suggestion on getting 64KHz source. Other ways also possible, this seems pretty straight forward.
http://www.z80.info/uexosc.htm

seems pretty straight forward.

Not as easy as I would have hoped, but I guess it will be fine. For the first link, they don't specify where the output is...any ideas?

Also, is there a way I can get 50% duty cycle?

Enable the outputs, and use the MSB, which will change hi/lo/hi/lo every 1/2 second.

right...

how exactly do I setup the crystal though?

I want to connect the 65.536kHz crystal to the clock of a binary counter. no microcontrollers involved.
Thanks!

Reply #24 has circuits to make the 64K oscillator that will drive the clock line.

But which would should I use? There are three on that page.

My counter chip is a 74393, i will be running the power supply at 3V (2x AA) and I will be using this crystal.

Whoops. Then how about 3x AA, which would be 4.5V?

Whops again.... I meant to say 74HC393. :frowning: Sorry for the confusion!

Try the simplest one first baum, if that works then you're all set.
If not, try another.

So the second one w/ 3 inverters and a 100N cap?