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There are 4 can lights on my ceiling controlled by a switch. I just recently installed smart light bulbs in all of the cans (they require constant power), Is there a way to keep constant power to the devices and also get power to a smart switch (that will not control anything from wiring) where I will run an automation to turn the smart bulbs on from the same box?

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    If I understand correctly, you want to replace the "dumb" switch with a "smart" switch? Before you undo a single wire, make sure you take pictures of everything! It will save you much heartache later when you can't figure out why it won't work.
    – FreeMan
    Commented Jun 10, 2020 at 11:25
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    Can you post photos of the inside of the switch box in question please? Commented Jun 10, 2020 at 11:53
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    Is this the only light operable by a wall switch in the normal location? Or is there another switch/light next to it? Commented Jun 10, 2020 at 13:57

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Yes a traditional switch just connects 2 wires together.

For lights controlled by a single switch there will be 2 main configurations you will see.

(colors are assuming US conventions)

  1. neutral at the switch. This is marked by a white wire(bundle) that isn't connected to the switch. And 2 wires connected to the switch.

    To install a smart switch there pigtail the wires connected to the switch together and add a wire to the neutral bundle. Those will be your live and neutral to power the smart switch.

  2. no neutral at the switch. This is marked by not having a non-ground wire disconnected from the switch. Often the white wire will be marked by a loop of tape.

    This is more complicated to adjust. Find the junction box where the switch-loop starts (often the at the light itself) and move the white wire going to the switch to the neutral bundle and the black to the live bundle. Then you can remove the tape loop marking the white as a live both at the junction box and the switch and you now have a live and neutral at the switch.

When multiple switches control the lights, there will be a set of 3 wires running between the switches: 2 travelers and either a neutral or a switched live. The process to convert is similar to above with the addition of an extraneous wire that you can cap off.

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Yes, normally there are two basic wiring configurations that both can work fine.

Lighting circuits in older homes often had a switch-loop connected from the first light in a circuit to the switch. A (re-marked) white wire fed the switch with a hot, and the black fed the switch leg to the lights. You would need to remove the first light fixture and connect all the whites together, then connect all the blacks together including the wires to the switch location, and replace the switch.

The current NEC requires a neutral at the switch for lighting circuits, this was allowed under previous edition of the code, but now required. This is either done routing the circuit cable with a hot and neutral first to the switch and then only a switchleg and a neutral are routed to the light, or a 3 conductor (BK/WH/RD) is routed from the first light to the switch with the black used as hot and the red as a switchleg. Either of those neutral-present methods at the switch location you just connect the hot and switchlegs together and to the smart controller, connect the neutral to the controller to the neutral and you are good to go.

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