Can someone get the circuit for a count-down timer. if possible, an explanation along with it.

thanks

 

Ok, basically, this is for a GCSE project.

i need to make a count-down timer to be built in with a steady hand toy

thing is, i have no idea where to start and i need things like tutorials with diagrams and stuff like that to help explain to me how to make this timer.

can anyone help

 

Are you looking to use logic chips or a microcontroller??

Kent

 

The only economical option i can think of is a custom programed microcontroller. anything else would be like a custom chip or something.

I'll get straight to the point: if you haven't had experience with microcontrollers, your at a dead end.

__________________
www.winpicprog.co.uk - Great PIC language tutorials.

 

If micro-controllers are "at a dead end", my only choice then is logic gates. can you give me a starter on how to do this?
thanks

 

What is this to mean :?: :?: :?: :?: :?:

This can be easy with a Pic and a few 7-segs or Lcd.

With the help of this Forum. :wink:

Good luck
Kent

 

I did one some time ago.

See http://www.electro-tech-online.com/v...=7350&start=15

It may be more complicated than what you need, but if you read through all of the posts, I expect you will obtain some benefit.

Using a PIC for a simple counter is like using a sledge hammer to crack a nut.

If you need more help, just ask.

Len

 

I would disagree, unless it's using a very tiny, very cheap, and very simple sledgehammer - as opposed to a larger, more expensive, more complicated, method of doing it.

The huge advantage of PIC's (and similar micro-controllers) is that they are cheap enough, and small enough, to use as replacements for many other chips. In this case the counter could be one single chip, giving far more versatility and capability than your relatively complicated multi-chip design.

Often the use of a PIC is massive overkill (personally I would quite happily use one to replace a 555, because of the vastly improved performance), but by making the project cheaper, simpler, and better, I see no problem with overkill.

However, the use of PIC's doesn't really apply to this thread, the question is for a GCSE project (UK exams you take at 16) - presumably it requires a hardware solution?.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

I thought you may disagree Nigel.

But if everything is done using PICs, hardware design skills will be lost.

Besides, I expect there are PIC projects that need some hardware around the PIC to perform functions that the PIC can't do, or is too slow, etc.

Len

 

We're in the 21st century now, many 19th century skills have been lost, and not being missed - I see no point in using antiquated techniques when a modern technique is far better than old primative ways.

However, as I mentioned before, as an educational exercise it's perfectly valid - it's just not cost effective as a practical project.

Yes, there are obviously many, and it's important that designers have the skills to do so - but it's rather like arguing that the project shouldn't use TTL/CMOS chips - it's losing the design skills of building the entire project from discrete components (and what happened to all the valve computer design skills?). Which strikes me as exactly the same argument that you are putting forward!.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Hey!

If u want to make it with CMOS, you should try the 4029, and a 4511 for the 7seg display.

E

 

go to http://www.allaboutcircuits.com/vol_4/chpt_11/3.html. it explains the up, down and the up/down counter.