Go Down

Topic: Noobie Question about the UNO (Read 139 times) previous topic - next topic

Hi guys, Just got my UNO and I've been doing all the basic projects with PWM, using my tact switches, etc. Very basic things trying to learn how this all works.

While doing some basic programming I forgot to set one of my pins to an output but even regardless I had a dim LED. Is there always SOME voltage available at each of the pins on my board?
Just trying to figure out why it acts like this? Once I set it as an OUTPUT it was the normal brightness.


Hope this is the right forum, couldn't decide between, micro controllers or programming.
thanks!

 :smiley-eek-blue:

JimboZA

Welcome.

If you have a squiz at this page, you'll see it says:

Quote
A pin may also be configured as an INPUT with pinMode(), and subsequently made HIGH with digitalWrite(). This will enable the internal 20K pullup resistors, which will pull up the input pin to a HIGH reading
That's what you were experiencing.

It's difficult sometimes to decide where to put posts yes: the mods are great and will move a thread if they feel strongly, and sometimes other members will suggest a move.

mrburnette

#2
Jan 02, 2015, 02:20 pm Last Edit: Jan 02, 2015, 02:25 pm by mrburnette
Hi guys, Just got my UNO and I've been doing all the basic projects with PWM, using my tact switches, etc. Very basic things trying to learn how this all works.

While doing some basic programming I forgot to set one of my pins to an output but even regardless I had a dim LED. Is there always SOME voltage available at each of the pins on my board?
Just trying to figure out why it acts like this? Once I set it as an OUTPUT it was the normal brightness.


Hope this is the right forum, couldn't decide between, micro controllers or programming.
thanks!

 :smiley-eek-blue:
Thank you for taking the time to explore and learn.  A good foundation will serve you well as you progress.

There is also another strange situation that you may encounter with low-power external devices that seemingly work but have not been properly wired... say maybe no connection to Vcc or no Gnd connection!  The term for this is phantom power or sometimes you see it as phantom current.  In this situation, one or more of the signal connections is "leaking" current into the external device... which is to say, either Vcc or Gnd is being referenced to a digital signal lead. So, if you start seeing strange things with sensors, double-check the power and ground connections!


Welcome to Arduino!

Ray
My Projects

Welcome.

If you have a squiz at this page, you'll see it says:

That's what you were experiencing.

It's difficult sometimes to decide where to put posts yes: the mods are great and will move a thread if they feel strongly, and sometimes other members will suggest a move.
Thanks for the quick reply!

The only weird thing is... i didnt set a pinMode() at all. Thats why I found it weird.
but anyhow thanks for that link. I read the entire page.


Go Up
 


Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

Arduino
via Egeo 16
Torino, 10131
Italy