Basic timer for toy...

Over the last couple of years I have been trying to figure out from scratch what I need to do to build a low cost timer for a toy. The toy will time how long a kid can maintain pressure on a switch. Here is what I want to achieve:

What it will do is, once a switch is engaged a small, backlit LCD will activate and display 4 numbers which will count up from 0 in seconds and microseconds. It need not be accurate, near enough is ok. It won’t need to count past 99.

When the switch is disengaged the timer will stop, and the amount of seconds that was reached will continue to be displayed for ~1-2mins, then the unit will go to a low or no power mode (to conserve battery life).

Should the switch be activated again while the time is being displayed I would like the timer to reset, and start counting from 0 again.

In an ideal world I would like the timer to last about 1800 times to count and it would count to an average of 60 seconds each time. The power needs to be supplied by a low cost battery, a small one is preferred as the whole unit should be able to fit into the size of an egg.

It would be disposable after approx 1,800 uses so the cheaper it is, the better. *

I have bought quite a few timers to reprogram, however they don't contain micros, just a black lump of plastic concealing what appears to be hard coded instructions. It looks like I can't get away with reprogramming an existing timer, but will instead have to build a complete new one, including printing PCB etc. But this is going to be too expensive for me.

I apologise for coming here and dumping these requirements on you. I have been trying to get this up and running for a while based on pieces of info I get online, but I find electronics a very difficult subject, so I would like to know if someone can tutor me in either building this thing, or frankensteining another timer to do what I need. Skype, email, regular phone, whatever. Im ok to compensate you (or a charity on your behalf if you like) for your time.

Again, sorry to do this. I will keep you guys informed on how I go solving this little problem. Cheers

Your project is a big step for someone starting in electronics, although can be done.

This forum prefere to talk Pic's for microcontrollers, i think the Picaxe chip is a much easier micro to start with but not well excepted on this forum.

If it was myself doing this i would use a Picaxe chip as it can do all that you need.
I think attempting this project without the use of a micro is pointless.

It would be helpful if you had listed your location in your profile, as then we would know what you have better access to, or who is local to you.

I fail to understand what the 1800 times part is that you quoted, and also how you hope to fit a lcd into a egg size area.
I think you have looked at some cheap lcd's used in toys and the size of these without realizing what is involved to drive a lcd.
The black blob chips on the board to drive these displays have a lot of purpose designed silicon for this application.

Pete.

Hi Pete

I am in Sydney, Australia.

Over the last while I have figured out that this is a big step for a beginner! So many dead ends and goose chases! But that is what it is about, or so they tell me... I appreciate your input Pete

I agree that a micro is the way to go. I would like to produce this in future so I might as well get it as close to right as I can.

The thing I am making is to go into a childrens toy I have in mind. The concept is that the child will try to accomplish various tasks while standing on a plate, and the toy will time how long they manage to do it. I expect that 1800 times doing this would be a fair qty to expect a battery change.

As accuracy is not an issue I believe that a crystal is unnecessary, and I am told that an 8051 micro could do the trick. I understand that a pic could easily do the same thing? Given the low cost and access to programming software I think this might be the go. Can I drive an LCD with a picaxe without the need for an LCD driver? Hopefully I am in the ball park with this!

I have looked into LCDs and found a 4 digit 7 segment display that measures 18mm high by ~40mm wide which I can hopefully use.

And thank you for interpreting the black blobs! I scratched one off and noticed barely anything... Cheers -Ben

Ben,

Yes you can drive a lcd direct with a micro, and its just a matter of what micro you use and what style of display you have to the requirements needed.

If you care to PM me a landline number i am happy to give you a call to discuss this further, as i get a little lazy with typing and a phone conversation covers much more.

Pete.