Clock pulse generation.

[Karthik rajagopal]

Hi,
I want to create a circuit which will generate clock pulse at the rate of 30 seconds for my digital clock. I tried using 555 timer circuit to generate a clock pulse, but that wasn't accurate. I tried searching it in Google and I saw few circuits using crystal oscillators. I haven't used these crystal oscillator and this is totally new for me. So, if you guys know any other clock pulse generation circuit, I request you to help me out. If crystal oscillators are the only way of generating accurate pulse, suggest a circuit that will fit my requirement.
Thanks in advance.

 

[Harald Kapp]

If crystal oscillators are the only way of generating accurate pulse, suggest a circuit that will fit my requirement.

Not the only way, but one with the best price/performance ratio.
Although so called mems circuits are digging their way into the crystal market with good performance at reasonable cost, too.

As you are not experienced with crystal oscillator circuits, you may want to use an off the shelf crystal oscillator at 32.768 Hz. This is the typical clock oscillator frequency as it is easily divisible by a power of 2 to arrive at a 1 Hz clock frequency. It is for this reason also comparatively inexpensive as it is produced in masses, Here is an example.

 

[Karthik rajagopal]

Not the only way, but one with the best price/performance ratio.
Although so called mems circuits are digging their way into the crystal market with good performance at reasonable cost, too.

As you are not experienced with crystal oscillator circuits, you may want to use an off the shelf crystal oscillator at 32.768 Hz. This is the typical clock oscillator frequency as it is easily divisible by a power of 2 to arrive at a 1 Hz clock frequency. It is for this reason also comparatively inexpensive as it is produced in masses, Here is an example.

What do you mean by a power of 2? Is there any soldered circuit boards in market that will generate this clock pulse? If it's available please explain me how to use it. I saw the hyperlink you sent but not able to understand what that is.

 

[Karthik rajagopal]

Another doubt that I have is that I didn't connect any capacitors to the 5 th pin of my 555 ic. Will that affect its accuracy while generating clock pulse?

 

[Harald Kapp]

Will that affect its accuracy while generating clock pulse?

Not much. The 555 is not a precision timer, considering that the best affordable accuracy for resistors is 0.1 %, for capacitors 5 %.

 

[Karthik rajagopal]

Not much. The 555 is not a precision timer, considering that the best affordable accuracy for resistors is 0.1 %, for capacitors 5 %.

Thanks for the clarification. I asked you whether there is any soldered circuit boards that are sold which will produce a clock pulse of 30seconds using crystal. Please help. If there are no pre soldered boards,then suggest me a simple circuit using these crystals to generate these pulse.

 

[Harald Kapp]

I don't know any, you'd have to search for them.

A simple circuit uses this oscillator plus a divider by 2^15 to create a 1s clock pulse. Then another divider by 30 for your 30 s clock pulse. Standard CMOS chips can be usedf or this, the internet is full of circuits to chose from. Or roll your own.