hi.. i am a newbie in using arduino duemilanove. currently i met a problem in the pushbutton arduino tutorial.
when i try to connect external 5V instead of the internal 5V of the duemilanove, the led lights up without me pressing the pushbutton. i am totally lose and not sure why i cant use external 5V as the input voltage for the pull up resistor.
Hi weihao, you can use an external 5 volts for pull-up (you must connect the external ground to Arduino ground) but why would you want to?
What do you want to do and how do you have it wired?
I am having the same problem without even an external power supply. This is a brand new unit
I get arbitrary pullups, where the light will switch on and off with nothing plugged in to it.
Also when I connect, it lights up and then I pull the cable the light stays high for about the count of 4 or 5.
Is this just faulty or have I fried something without even trying. I'm not even doing complex things, I am just testing out basic functionality.
Are you using an internal or external pull-up resistor on the input pin? You can read more about pull-ups here: http://www.arduino.cc/en/Tutorial/DigitalPins
This also means however that input pins with nothing connected to them, or with wires connected to them that are not connected to other circuits, will report seemingly random changes in pin state, picking up electrical noise from the environment, or capacitively coupling the state of a nearby pin.
:-[
Well then??
I guess it's obvious I have still does not know what he is doing written all over my face. Thank you very much.
It seems I have lots of reading ahead of me still.
I will re-evaluate what I am doing and see if I still have any problems
Don't feel bad, Arduino is all about doing cool things even if you don't quite know what you're your doing. Have fun!