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I've seen videos on youtube about how to emulate a keypad on arduino. Some of them includes a resistor while others do not. What are the difference between them and are there advantages in doing one over another?

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    \$\begingroup\$ we can't judge the motivation behind schematics based on videos. Even less when we haven't seen either. Please add the schematics (and not just video links) to your question. Thank you! \$\endgroup\$ Nov 23 at 12:48
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    \$\begingroup\$ (also, and this will probably not come to you as a surprise: the vast majority of technical videos on youtube is made by people who have no significant clue, and are just copying things from websites that themselves copied... you get the idea. There's money in views, not in good designs and correct information) \$\endgroup\$ Nov 23 at 12:49
  • \$\begingroup\$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. \$\endgroup\$
    – Community Bot
    Nov 23 at 12:56
  • \$\begingroup\$ One has resistors, the other doesn't. The AVR has internal pull-up resistor options on its I/O pins; perhaps one of the designs uses those? \$\endgroup\$ Nov 23 at 14:33
  • \$\begingroup\$ I'm very sorry, I have only recently picked up this hobby and I have little experience on this topic. Thank you for all your answers, I will ask a better question next time once I have studied enough about arduino. \$\endgroup\$ Nov 23 at 15:44
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Since the Atmega has internall pull-up resistor (50k) on Pins there's no need to use external resistors until you need to meet some special criteria. Just enable pull-up resistor on Pin you are going to use, connect button between this Pin and Gnd and look for signal Low in software.

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