Problems with analogRead

Forum 2005-2010 (read only) Hardware Troubleshooting
1

i'm noob with analogic electronics....

can anyone answer those questions?

why do i get large oscillation values from any analog port even though it isn't linked to any circuit'???

are there any diference between the analogRead and the voltimeter values????

thanks

2

If the analog in pin is not linked to any circuit, it is floating, which means it can read any value. What is the purpose of reading the value from a pin that is connected to nothing?

3

oh it was just a test i made to see what value i got... and when a i saw that oscillation i was worried thinking my arduino is crashed or something like that

thanks for the explanation

4

If the analog in pin is not linked to any circuit, it is floating, which means it can read any value. What is the purpose of reading the value from a pin that is connected to nothing?

Isn't that an okay way to seed your random number generator? :slight_smile:

5

There are certainly entropy generators which use background noise as an entropy source (sadly the only one I can think of off the top of my head comes from sparkfun].

Many use only a few bits from the acquired signal though; IIRC this has something to do with Johnson noise being Gaussian.