Aren't LEDs DC power?

[MrSurly]

Just to add to the discussion, the "tape light" LED ribbons that are sold as 12V are made up of individual SMDs (the LED "bulbs") which have nominal ratings of 3.6V and they are connected as ~paralleled ~series-connected~ three bulb groups. Each group connected this way functions as a 12V load.

 

[PhysicsDude]

Just to add to the discussion, the "tape light" LED ribbons that are sold as 12V are made up of individual SMDs (the LED "bulbs") which have nominal ratings of 3.6V and they are connected as ~paralleled ~series-connected~ three bulb groups. Each group connected this way functions as a 12V load.

Right... but this setup is inherently inefficient (as far as LEDs go), since the 3.4 or 3.6 or whatever nominal LED voltage drop is only 10.2~10.8 volts for 3 LEDs. Which means roughly 2 volts are dropped by the load resistor, effectively wasting 15-20% of the energy you put into the light strip.

That's why commercially sold light fixtures or bulbs don't run off 12V. Its only a novelty thing so that you can use them on cars, and DIYers can cut the strips every 3 LEDs to fit their project, and use generic 12V power supplies instead of having to find drivers to fit their specific application.

 

[checkthisout]

I don't know the history behind it, but every military tactical vehicle (and aircraft, I think) I've worked with has been set up to provide 24 volt power for radios and other accessories.

IIRC, the older mil-spec vehicles (duece and a half, etc.) also ran the truck off 24 volts, but when they started buying commercial vehicles (CUCV, etc.) to get lower prices they installed a split system where the vehicle uses 12 volts, but the alternator still charges two batteries that provide 24-28 volts for the equipment.

Bruce

It's to keep the military stuff universal. Larger Diesel vehicles I.E. busses, OTR trucks etc, all use 24V systems because 24V means smaller starters, smaller wiring etc.

It's a lot more interesting when you accidentally cross-connect jumper cables or having a wiring short with a 24 VS 12 volt system.

 

[Platonic Solid]

Solar powered DC LED lighting would be the peak of efficiency via cheap 95% efficient DC-DC buck drivers.