Help - small digital counter

[JimS]

Hi All

I’m looking to make a small digital display counter.
All it has to do is display two 1 digit numbers and be able to add or subtract from those numbers in increments of one. Ideally it would have four buttons, two buttons for each digit (one button would increase the number and one button would decrease the number).
I’ve been thinking about using a cheap LCD watch for the display, because it is the size I want. I have taken the watch apart and the display, PCB, battery, plastic housing (the whole assembly) is the perfect size for this project.
What I want to know is there any way to modify the function of the watch. The watch has many functions but all I need it to do is add and subtract numbers on the display. I’m guessing there isn’t because the watch is not set up to do that.
I’m guessing I’ll have to use something else for this project. What I’m looking for in this project is: a two digit display counter that I can add or subtract numbers to each digit, and is about the size of a quarter in diameter and about ¼ inch thick.
Any thoughts or suggestions would be greatly appreciated.

 

[Harald Kapp]

Maybe this fits your requirements: https://estore.ti.com/eZ430-Chronos-433-Chronos-Wireless-development-tool-in-a-watch-P1734.aspx
Well, maybe not the bill...

Harald

 

[JimS]

Thanks for the input, but that’s not what I’m looking for. I want to make this project inexpensively. The digital watch that I am using came from the dollar store ($1.00), though any inexpensive parts will do.

 

[timothy48342]

Reinventing the wheel so you don't have to buy those expensive wheels from those darn wheel-people! I love it.

No, really. I'm not being sarcastic. I think its great that your using a cheap dollar store watch for parts. Purchasing integrated development systems might be better in some ways, but your way is much more fun.

I took apart a tiny calculator and the LCD display seemed simple enough, but the connections the the circuit board were so tiny, I didn't think I would ever be able to attach them to anything else. Is that the situation with the watch? In the calculator it was a plastic strip with conductive pathways and there was no solder. They must have used conductive glue. I am imagining that the tiny display of the watch is connected in a similar way.

You won't be able to use the circuit board of the watch, because it is set up to be a watch, rather than what you want. You might want to leave the display attached to the board if you can't duplicate the way it is connected, and just desolder everything else from the board and use that board as just a connecting point for the display.

Now just design your circuit and jumper the 10 or 20 connections from your new board to the 10 or 20 traces that lead to the display on the original board.

Your desired circuit does not seem all that tough to make. However it would be tough for me to make. That is beyond my skill level. (I find it much easier to take things apart then to put them together.)

Good luck. Following the thread,
--tim