Instructables

Multiple Photocell Problem (Arduino)?

Hello, I have a problem with using more than 1 photocell. I am using the AnalogReadSerial example to test each one and they are giving me junk. I have tried just one wired to the board and it works fine, but when i wire 4 into a breadboard it gets messy.
                                                                                    
                                                                                            Here are some pictures

                                                                                                                   

Picture of Multiple Photocell Problem (Arduino)?
Photocell_Not_Working.jpg
What resistor did you use ?
D5quar3 (author)  steveastrouk1 year ago
1K ohm. I have tried multiple resistor values, and I still get the same problem
Try putting a good 100nf cap across each cds cell, to try to reduce noise. What are you actually seeing coming out?
D5quar3 (author)  steveastrouk1 year ago
I figured it was the 5v and ground rails on my breadboard needed some jumpers, after that I was getting steady numbers.
Libahunt1 year ago
Use a short delay each time before moving on to read next sensor. Something between 2 and 10 milliseconds should be enough.

Explanation about the need for a delay in second reply there:
http://forums.adafruit.com/viewtopic.php?f=25&t=11597