2 sources for same LED strip

[robman14]

Hi guys, the next problem I'm trying to solve is....

I have 2 led strips going down either side of my party bus.
I tapped into the 12V supplies (at the front of the bus) that powers them when the bus door opens.
But I also want to be able to turn them on from a switch at the back of the bus.
I have a 12V supply, on a switch at the back, but how to property wire to LEDs? I'd love to be able to connect to the other end of the LED strip, and avoid running wires 20' to the front, but not sure that can be avoided.
The problem is....the switch could be on, and the door could be opened, so it would then be getting power from both ends.
Advice? Thank you.

 

[alpg88]

you can do that, i've done it many times, powered led strips from both ends, just wire them the same way you did in the front.

 

[robman14]

you can do that, i've done it many times, powered led strips from both ends, just wire them the same way you did in the front.

no problem if the strip is getting power from both ends at the same time?

 

[alpg88]

I never had an issue, but if you are not sure try it with a short piece of strip, before wiring the long one, the strip will work just fine, However no one knows how your bus is wired, and whether or not you will damage your wiring, or whatever else they power, in theory you should not have any problems if wired correctly, worst thing you'll blow a fuse.

 

[Dave_H]

You could wire your switch to a small 12v relay which would switch the lights on/off when powered from a single source. That would mean running some thin wires down the other end.

If you power with separate supplies, each could have a series diode, to isolate the two sources. This is common in redundant telecom power busses. If both are enabled, depending on relative voltages, you could get some current sharing, but that should be no issue if both sources are able to handle full load individually.

The downside is one diode drop in each supply, depending on the current (how much is involved here?) You should be able to keep drop to under 1v, lower using Schottky rectifiers.

Dave

 

[Galane]

Connecting power at both ends of an LED strip, addressable or not, is a common thing, especially with 5 volt strips. It's called "power injection". If you're stringing together 800 LEDs it's a good idea to connect power at both ends and in the middle.

The thin metal traces on the flexible strip have quite a bit of resistance so voltage will drop. For a 12 volt strip the length of a bus, the drop shouldn't be enough to affect the brightness at the far end from the supply.

You could do a 3-way switch circuit so they can be turned on or off from either end, no matter if the switch at the other end is on or off. Then wire in the door switch in parallel directly to the strips so if they're off they'll come on when the door is opened, but if they're on the door won't affect them.