I have tiny christmas tree that has about 20 small LEDs, which are powered by 2 AA-batteries. So I'm assuming the LEDs are 3V (because of 2 AAs). This tree was bought in a store, as is.
What I want to do, is hook up the little tree to an Arduino and control the lights with some sensors (lights, sound, etc). I was planning to just connect the battery terminals to the 3V Arduino output.
Is it safe to assume that the battery pack has a built-in resistor somewhere and I can just safely connect it to a 3V output of the Arduino, or would it be wise to have an extra resistor somewhere?