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Topic starter
2020-04-19 2:54 am
The example wiring diagram in the shift register presentation uses individual pull down resistors for each switch connected to the 74HC165. Could not all the switches be connected to a single resistor which is then connected to ground, especially if only intend to use single switch at a time?
Topic starter
2020-04-19 1:27 pm
I suppose if you are going to use resistors, one could also string a series of them in a multistage voltage divider and connect switches at each junction point. Then each switch would output a different voltage that could be fed to a single analog input. Power, ground and one analog pin would be all that is needed and not 74 chip. I assume this is how a keypad by ILS I saw on Amazon works?
2020-04-19 2:27 pm
No, that wouldn't work, you would be literally shorting all of the inputs together! Take a look at the schematic and you'll see what I mean. The pulldowns keep each digital input low, pressing a switch brings the input high.
I assume this is how a keypad by ILS I saw on Amazon works?
Yes, I have already covered that keypad in my LCD article and video, it uses one Arduino analog input. But, of course, that's a completely different subject!
😎
Bill
"Never trust a computer you can’t throw out a window." — Steve Wozniak