I am attempting to power up battery powered (4.5V) LED strips and an arduino with the press of one button.
I read that you can have multiple voltage sources sharing a common ground, and I am trying to use that to switch everything on and off.
This circuit was working when before I swapped out a weaker 9V battery (was down to about 5V) with a fresh one. After swapping, the arduino is now powering on, without the switch being engaged.
What am I doing wrong?
Thanks!!
Your diagram does not show the correct connections of the LED strips.
The red lines to the LED strips and to the Arduino differ by 9V-4.5V = 4.5V, that's sufficient to let current flow even if the switch is off.
I'd power both the Arduino and the strips from the same 4.5V battery, and switch the +4.5V line from the battery. An Arduino will work with 4.5V on Vcc, bypassing the on-board voltage regulator.
Get a switch with as many poles as you have connections coming off the + of the batteries
