I am building out an enclosed trailer for work that I am adding interior LED strips to for lighting as winter is arriving and it gets dark pretty early. I would like to be able to power the lights in 2 separate ways. One way will be to tap off the existing switch & incandescent light (light will be eliminated) that came with the trailer that operates while connected to my truck when its hooked up; that's the easy one. I am a builder so the trailer is dropped at a customer location 99% of the time. I am adding an AC plug on the exterior that will power receptacles in the trailer and an inverter that will power the LED strip lighting. My question is do I need to do anything special with relays, or as long as both power sources (truck or AC power) aren't connected at the same time will I be fine? Please excuse my offensively crude drawing. To summarize: LED strips powered by 12v truck power OR ac inverted power, never powered by both at the same time. Both ways are fuse protected. Can I just wire this up straight forward or will I need any kind of relay? Thanks so much!
Best bet is always power from Truck battery and use 10A 14V trickle charger for battery from AC that is hardwired to battery with AC plug , with plug under front hood or mounted somewhere conveniently. LED strings vary in current , so measure what you need , maybe 5A is enough. This way battery drain is nill.
You could use a relay, with the normally closed side to truck power, and the normally open and the coil to the AC inverted power side. If AC is present even while the truck is connected, it will use the AC side automatically.
You could use a simple diode or bridge. One diode on each side. Whichever voltage is higher will power the leds. You would need to connect the grounds together for this.
Or the simplest thing. A on-off-on dpdt switch. You manually select which power to use, or none at all.
If the current is too much for the switch you may need to use a relay anyway though.