Hello, I think this is a simple question. I have a project with seven buttons. Can I use one common 10k resistor, or does each button need its own?
An interesting question, in 99% of cases for each “input per button”, you’ll need a resistor for each input (that could be using the internal INPUT_PULLUP)
However, you could look at implementing a matrix as one alternative… no resistors.
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Wire your switches as S3 in the schematic below.
You look for a LOW if the the switch is closed.
No external resistors are needed since the internal pull-up is used.
Thank you for your response. I was going to use pull-up, but had read that for long wire runs I could have issues. My buttons will be located about 10m from the Arduino.
30 feet will probably cause noise problems from the wires.
Best to use an interface circuit when the wires are that long.
Google Opto-isolator.
If you insist, add 0.1 to 1uF on each input to GND ( close to the Pin).
If you have problems, external strong Pullup of 1k could be added (at the Arduino).
Normally closed switches (to GND) would be another consideration.
Why not draw 2 schematics showing how you plan to wire the buttons with one resistor Vs 7 resistors? Then we can help you understand how to predict for yourself what will happen. This will be more useful to you in similar situations in future, than just giving you the answer today.
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