How can I add a switch into an existing circuit but only control some of the circuit?

Question

I'd like to put all the lights in my unfinished basement on one switch. I've got carpentry experience but only novice level wiring experience. Right now the lights are all on pull-chains. The electrical run that these lights are on also feeds lights in parts of my finished basement (stairwell and a finished guest room). I drew a diagram of the current wiring scheme below. Note, the partitions I drew under the wiring scheme are how I eventually plan to partition things (also adding a new finished room in the future). What I'm asking about right now is the area partitioned as "current unfinished space". I'd like to add a switch that controls all those lights (3 of them) but the switch shouldn't control any of the "soon to be new room", stairwell lights, or current finished guest room. Do I just need to put a junction box before the first light (and after the last) in the chain and run a wire by-passing the 3 lights from the stairwell to the guest room? Then from that same junction box, power the 3 lights/outlet in the current unfinished space? That seems to make sense to me, but wanted to make sure I wasn't making it more complicated than it needed to be (i.e. simpler solution?).

Also, assuming that's what I have to do, I'll need to re-wire that electrical outlet so it's not turned off/on by the new switch as it's currently wired, right?

This is all unfinished space so obviously I have access to the walls/ceiling. Any help/advice would be appreciated!

Answer 1

As you have drawn it, these lights will be always-on. Most people do not want that, though it is becoming more popular due to LED lights drawing so amazingly little power.

Imagine with your mind's eye, if the colors of wires were related to their function. Start with

• black for the "hot" wire, that is always hot regardless of any switch positions.
• White for the "neutral" wire, which is the normal current return.

Current flows in loops, so the two wires above are bare minimum. Now let's think about a third:

• Red for "switched-hot", a wire that is hot when the controlling light switch is on.

Normally we are stuck with the colors that are in cable, and don't get to color-code like this. But in this particualr case, I think it will work out. If not, they make colored electrical tape.

Now, light switches need all 3 wires. If you heard that light switches only need black and red, and you can do that with black/white cable, that knowledge is obsolete. Switches need all 3.

Lights need 2 wires: switched-hot and neutral (red white). They don't need always-hot (black) unless you want the option to jumper them on 24x7, but it's ok for always-hot to pass through their box untapped.

So the deal is, you need to run /3 cable (red black white) between all the controlled lamps and the switch. The switch taps black and red, leaves white capped off for future smart switch use. The lamps tap red and white, and black passes through.