Voltage Generated By each Key Press

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Thread Starter


Joined Jul 24, 2014
I wanted to calculate the voltage that each key press that is generated by our keyboard. Naturally I can always connect a voltmeter between the both data lines(D1, D2) by opening up an USB Keyboard. I also read that each key press generates an ASCII code that goes for processing. But im concerned with the voltage, so is there any method by which i can obtain these voltages, because I really cant resort to clipping up the wires and connecting it and checking it for voltages.
Or is there already any such result available on the internet?
Thanks Guys ur help is really appreciated.


Joined Jun 5, 2013
Measuring a voltage is meaningless, it will always read 3.3V or -3.3V. The signal is digital, it is the sequence of signals that determine what key has been pressed.

Hmm yes if keyboard as stated as a digital device, then my question is meaningless. Thanks for correcting me
but the keyboard isolated is a physical device, which needs electrical power to operate, and hence on key press an electrical voltage assigned to each key is generated as a signal which gets converted to correcponding ASCII value which then needs to be converted to machine language or say binary to be processed and then similarly the output is displayed depending whether is is a monitor or printer or whatsoever


Joined Oct 2, 2009
Not true.

Modern keyboards are built using membrane switches printed on sheets of plastic.
Each individual key is a mechanical/electrical connection between two contacts. No voltage is generated.
There are over 100 keys to detect. A microcontroller chip (MCU) embedded in the keyboard scans the keys using a matrix pattern in order to detect which contacts are closed. Only then is the MCU is able to send a keycode (not ASCII) to the main computer.

The only time keyboard switches generate a voltage was when keyboards were built using Hall Effect sensors over 50 years ago.


Joined Mar 13, 2020
By now you've come to understand that pressing a key on a keyboard doesn't generate a voltage. Instead, as explained, any alpha character pressed, whether caps or lower case will generate a digital signature the computer recognizes as a particular alpha data. For instance, when you press a capital A the digital transmission is at 3.3 volts and you get a series of 0's and 1's. The digital representation of a capital A is 01000001 .

Here is a website you can try. Type any key in and you'll see the result in digital form.


Joined Dec 31, 2017
For instance, when you press a capital A the digital transmission is at 3.3 volts and you get a series of 0's and 1's.
I suppose the series of pulses could be average and filtered producing a dc voltage but it seems like the difference between keys would be too small to be usable.
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