| Electronics > Beginners |
| Pull down resistor question |
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| Alfgan:
Hello everyone! Should I place pull down resistor near button? And if I should, what nominal it should be? |
| boffin:
--- Quote from: Alfgan on August 27, 2019, 05:27:03 pm ---Hello everyone! Should I place pull down resistor near button? And if I should, what nominal it should be? --- End quote --- Yes, perhaps, and maybe. Depends on what you're using it for. In some cases you don't need a resistor at all as what you're feeding may already have a pullup (or pulldown) resistor. Case in point, the Atmel processors used in an Arduino, have a pullup you can enable with INPUT_PULLUP(aka pinMode(2,INPUT_PULLUP); to enable the pull up resistor. The only thing thing is you'll be hooking your switch from pin to ground instead, and your reading will show 0 when pressed and 1 when released, but that's easy in software. |
| Alfgan:
Thank you for information :) So in the situation above I do not need pull down or pull up resistor? This is a 555 dice and I want the dice to start when I press the button. I am not using arduino there. |
| Audioguru again:
It is obvious that a pulldown resistor parallel with the pushbutton would keep the circuit acting like the pushbutton was continually pressed. Then the 555 would keep the LEDs spinning continuously. The transistor already has a pullup resistor (3.3M) that helps to turn it off as the 1uf capacitor discharges after the pushbutton is released. |
| Alfgan:
Oh thank you very much. |
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