Broken analog inputs?

Forum 2005-2010 (read only) Hardware Troubleshooting
1

Hi,

when im reading value of analog pin's, some pin give strange values.
I think pins 0,1,2,3 works, but others are broken.

I made program and it read analog input pins. (all are empty pins, and I have Mega) First number is pin number and after "=" is value of that pin. It give next result:

0=326

0=314

0=319

0=275

0=277

0=295

1=305

1=291

1=326

1=313

1=294

1=330

2=303

2=280

2=308

2=293

2=266

2=304

3=291

3=278

3=307

3=298

3=279

3=309

4=1016

4=1020

4=1016

4=1020

4=1017

4=1020

5=1018

5=1020

5=1018

5=1020

5=1018

5=1020

6=1019

6=1019

6=1020

6=1023

6=1020

6=1023

7=1019

7=1023

7=1019

7=1014

7=1020

7=1016

8=1022

8=9

8=7

8=10

8=10

8=9

9=133

9=1023

9=11

9=8

9=1020

9=1015

10=13

10=7

10=12

10=13

10=16

10=6

11=500

11=1009

11=14

11=8

11=1014

11=15

12=7

12=10

12=1016

12=10

12=9

12=9

13=93

13=7

13=10

13=9

13=6

13=10

14=16

14=8

14=11

14=5

14=8

14=11

15=512

15=12

15=4

15=20

15=3

15=7

Some pins give first value "10" and after 300 milliseconds it give "1000".

Is it broken or is this Normal?

2

Probably every thing is normal. Two points:

  1. Reading analog input pins when there is nothing wired to them returns random noise values. Wire the pin to ground or +5vdc when testing and you should get values of 0 and 1023 respectivly.

  2. There is a bug in the Arduino Version 17 where only the first 8 analog input pins function correctly (pins 0 to 7). There is a patch to a core library file that will fix it, otherwise it will be corrected in version 18.

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1250970792

Lefty

3

I connected them to ground, pins 0,1,2,3 values are 0, and couple of nexts gives about 10 and some of next give still quite random values

Problem is when I connect Infrared Proximity Sensor. It works on pins 0 to 3, but not others... then value is only "600" or random.