This is my first post to this forum, and I am a beginner with electronics. I am an aerospace engineer who has gotten a little lost in this foreign land of electronics, but I find it very fascinating and am trying to learn as much as I can!
I am working on a school project where I have a system set up that includes LEDs, magnetic switches, a Waveshield for playing audio, and two small servos. There are two Arduino Uno's: one controls the Waveshield and the other is the "big boss" that controls all the other components, in addition to controlling the first Arduino. The "boss" Uno controls the other via a shift register sending signals to individual pins on the other. (I figure this is super inefficient, but that is how it is currently working)
My problem comes when I switch my power source from my laptop USB to an external power source. I get erratic behavior from the "boss" Arduino's signals to the other Arduino. Via the serial monitor I see an output that says the shift register from the "boss" Arduino will randomly be sending a high value instead of low at a pretty consistent rate and it switches very quickly.
What might be causing this? Any help is appreciated!
I will work on making a schematic, but finals week is coming up so I may not have much time... However, could you explain what you mean? They are not connected to a common ground if that's what you are asking. Do I need to be doing something special to ground them when I am using an external power source that is not necessary when using laptop usb ports?