# countdown clock

#### gizerandboots@sbcglobal.n

Joined Jul 24, 2008
3
hello everyone,

Im not an electronic savy person what im doing hear is trying to kind a countdown clock for my christmas display.

I have looked around the web and im not willing to spend $300 plus. I was hopeing one of the real smart people here would be able to point me in the right direction to build my own. now i have built a christmas light sequense controller so I am able to build electronic stuff, i just need the design, what im looking to build is a display showing days, hours, min, sec, and mili sec would be real cool, and would like the display to be 4 inches tall or so and have it countdown to a particular day i program in (in my case christmas) Can this be done for around$100???

any help would be welcome

THANKS,
scott

#### Wendy

Joined Mar 24, 2008
21,847
The short answer is yes, but the catch is finding the plans. The parts aren't that expensive, but it will take know how.

#### SgtWookie

Joined Jul 17, 2007
22,201
This is one of those calendar and time manipulation problems that would lend itself wonderfully to a microcontroller.

There are plenty of time and date manipulation algorythms out there.

There are modules that can obtain the precise time from NIST WWV's 60KHz signal.
http://tf.nist.gov/stations/wwv.html

It's just a matter of hooking them up, and writing the code to calculate the difference, and display it on something.

#### gizerandboots@sbcglobal.n

Joined Jul 24, 2008
3
This is one of those calendar and time manipulation problems that would lend itself wonderfully to a microcontroller.

There are plenty of time and date manipulation algorythms out there.

There are modules that can obtain the precise time from NIST WWV's 60KHz signal.
http://tf.nist.gov/stations/wwv.html

It's just a matter of hooking them up, and writing the code to calculate the difference, and display it on something.
your last sentenance is my whole problem or should i say chalange.

Last edited:

#### SgtWookie

Joined Jul 17, 2007
22,201
Your last sentence is my whole problem, or should I say challenge?
Well, what kind of research have you done?

BTW, we have no clue where you live, so we don't know if the NIST WWV time signal is even available or relevant to you.

In the meantime, look up the datasheet for a U4226B IC. It's a time code receiver.

Unless you integrate a timecode receiver into your design, your microcontroller (below called uC) predictions might start off OK (if you've set the time correctly) but will soon drift through the "well, close" category to the "wildly inaccurate" realm.

Plainly speaking, it's impossible to achieve decent long-term accuracy (stability) with the internal clock of a uC. It's very difficult to achieve even with very expensive equipment.

That's where the timecode receiver comes in. You can get the exact time loaded right into your uC, if you can figure it out.

You have a rather steep learning curve ahead of you. Even if you make no mistakes, your costs could easily exceed your target budget, depending upon which uC you start with, and your ability to learn the language spoken by it.

#### gizerandboots@sbcglobal.n

Joined Jul 24, 2008
3
Well, what kind of research have you done?

BTW, we have no clue where you live, so we don't know if the NIST WWV time signal is even available or relevant to you.

In the meantime, look up the datasheet for a U4226B IC. It's a time code receiver.

Unless you integrate a timecode receiver into your design, your microcontroller (below called uC) predictions might start off OK (if you've set the time correctly) but will soon drift through the "well, close" category to the "wildly inaccurate" realm.

Plainly speaking, it's impossible to achieve decent long-term accuracy (stability) with the internal clock of a uC. It's very difficult to achieve even with very expensive equipment.

That's where the timecode receiver comes in. You can get the exact time loaded right into your uC, if you can figure it out.

You have a rather steep learning curve ahead of you. Even if you make no mistakes, your costs could easily exceed your target budget, depending upon which uC you start with, and your ability to learn the language spoken by it.
thanks for your help it looks like what i need to do is buy one.