Versatile and Low Cost Digital Counter

Step 2 Testing and Disassembly

First, turn on your calculator and press: "+ 1 =" It should display "1." Now (This is very important), press "=" again. Does it read "2" as the answer? If yes, continue foreward. If not, you need a different calculator that will do this.

The fun part -- take apart your calculator. With any luck, your calculator uses a graphite pad to close the circuit on a printed circuit. Just like most keyboards. You want a calculator that you'll be able to solder onto - so if your calculator printed circuit is printed on a plastic - you're likely to have a lot of trouble (like I did).

Now locate the printed section for the "=" button and fire up the soldering iron.

Comments

[manicmonday]

Oops. Correction. It worked for a few minutes correctly, then the stiff wire started causing the "=" to go off on it's own multiple times. So then I tried another wire that wasn't so stiff, and it worked for a few minutes, then stopped getting connection. So, unless someone knows of a glue that is also a conductor, then that kind of calculator doesn't work for this application.

[DIYShared]

Look at my page how to do it with that kind of calculator: http://diyshared.com, click on Homemade Measuring Wheel. I have put also instructions on how to do a kind of conductive glue.

[beehard44]

graphite mixed with glue will do the trick
you can shave pencil leads for the graphite, should be mostly graphite over glue

[XOIIO]

Ta-Dah!

[PyroMonger]

there is a type of conductive glue but thats all I know on the matter. I don't know what its called or where you can get it from, sorry

[XOIIO]

Ta-Dah!

[manicmonday]

I bought that exact clear calculator, and it was easier than another than had an actual PCB. I wasn't able to solder the PCB at all, and that was if I was right about the place to solder it anyway. It was very confusing. But the clear calculator was much simpler, and I noticed that there were holes at critical junctures. I placed stiff wire in the 2 holes that lined up with the "=", bent it double, and crimped it down. It was no problem.

[thejrb]

yeah man i agree not sure were to connect the wires

[polavision]

can you post a picture of the wires soldered to the board? I'm not sure exactly where to connect them... thanks