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Topic: CASIO calculator and Arduino; joining circuits of different Voltage (Read 3676 times) previous topic - next topic


Apr 20, 2013, 07:48 pm Last Edit: Apr 22, 2013, 12:29 am by RonaldPoFo Reason: 1

I'm trying to hack a CASIO fx-85ES calculator:

I want to use the calculator as a keypad (arduino knows what button you pressed) and display (arduino "presses" a button), using an Arduino Pro Mini (5v).

buttons are pressed by connecting two contact points on the board:

for example: K07 + KI5 = "1" or K01 + KI2 = "4"
I only want to use the following keys: 0-9, +, -, x, :, =, and ")". total of 16 buttons

I plan to:
Connect points using transistors "press buttons". (is there a way the arduino can do this without transistors)
Use pins as input to read buttons pressed. (or more transistors?)

Note: I will only use calculator as INPUT OR OUTPUT never both at once.

Anything I forgot or suggestions? what do you think, could this work? :P


Would I damage the arduino by feeding the contact points on the calculator to it as inputs?
Do I have to join GND like when wiring a Servo????  (1.5v cicuit of the calculator and 6v circuit of the arduino)


It is not clear what you are asking.

You want to use the Arduino as a substitute for the keypad?

And also to read the calculator's keypad (key strokes), when that is used?
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!


An arduino Pro Mini 5v to:
-Know when a button on the calculator is pressed.
-Press buttons on the calculator(buy connecting two connection points)

Know when a button is pressed by reading a change in voltage between connection points.
Use transistors to connect two connection points, transistor's base (B) to arduino.

Will feeding a cable from the connection points on the calculator to the arduino damage the arduino? or even work?
Can I join two connection points on the calculator using the arduino, not transistors? ( the two connection points have to be wired one to another, NOT to GND or Vcc)


What does this mean:
quad buffer/line driver with 3-state outputs controlled by
the output enable inputs
I tried goggling around but I don't see how it should help?


it means you can use this chip to have 2 different components that use different voltage talk to eachother, ie 3.3v to 5v. its a buffer between the 2.


Would I damage the Arduino by feeding input and outputs to and from it without any isolation? (transistor, optocoupler)



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