Trying to power up an Arduino and Battery pack for LEDs with one switch. Help?:)

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.

Click here for larger image

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?


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

You need a double pole double throw switch.

Tom.... :slight_smile: