[SOLVED] 1 Hz clock pulse for digital clock

[yingyingong]

how to design a circuit that uses TTL ICs to generate 1Hz clock pulse for digital clock? all the design that i found are using CMOS. anyone can help?

thanks in advance

 

[mvs sarma]

It is better to use CMOS logic to have lower power consumption, higher noise immunity etc.
how ever , if you have to use TTL only, perhaps you can try NAND Schmidt gate for 32.768KHz crystal oscillator. Later , use binary counters to get 1 sec pulse.

 

[pointyhat]

You could do it with a simple 32.768KHz XTAL oscillator then divide it a few times with a prescaler/divider or a chain of D-type flip-flops (ripple counter). However, TTL really is a waste of time here.

You can use a single 74HC4060 as an XTAL oscillator (at 32.768KHz) and a 14 stage counter/divider. It has both inside. That will give 2Hz which is pretty close - just chuck the output through a D-type flip-flop to divide it again for 1Hz.

**broken link removed** <-- XTAL circuit + divider

 

[mvs sarma]

Perhaps it is a home work practice to learn TTL logic gates usage.

 

[yingyingong]

but the rest of my design is using TTL. if i'm using CMOS, is there anyway to connect it to run my TTL ICs that i've designed?

 

[mvs sarma]

you can level shift and use it.
instead of using CD4060, you can use 74HC4060 and it is TTL compatible.

 

[dr pepper]

Or a 74act4060, act series are designed to be connectable to 74ls logic, I've used 74hc logic with ttl it does work fine.

This probably wont apply to your application, the counter chip that divides the frequency down to 1 hz will be accurate over a period of 1 second or more, however if you need accuracy down to a microsecond then you'll need a sychronous counter or a gating circuit that synchronizes the output with the oscillator.
An asynchronous counter will have very slight jitter on the output, over time this will cancel out.

 

[yingyingong]

this is the circuit that i've drew? can anyone tell me where i did it wrongly?



how bout the one using 4060? is there any full circuit that i can refer to?

 

[mvs sarma]

how the crystal,oscillates without any active element l? here is the link to the element , under section "improved 1 sec pulse generator"
http://www.mcamafia.de/nixie/ncp_en/ncp.htm

 

[yingyingong]

if follow the the nixie clock generator, 4013 cannot connect to 74LS393 and the rest of the circuit which are TTL. am i correct?
therefore, i've connected the pin 3 of 4060 to the CLK if 74161 and Qa will be 1Hz right? can this work?
and how can i calculate the value for the capacitor and resistor? i can't get the value shown in the nixie clock generator. can anyone help me?