Re: Natedog's figure bashes and customs - Sandtrooper pg29
Well unless my calculations are way off or I'm not understanding something.
26 Cathode sabers x 350mA = 9.1A
5M 5630 LED Strip = 6A
18 LED puck lights x 100mA = 1.8A
Thats over 15A right there. Plus all the other stuff in the room. I'll check my fuse, maybe its not 15A after all.
DC on the supply side. That doesn't mean that's how much you're consuming from your home's circuit. Look at the various adapters powering those devices. They will have input power characteristics - they will be printed as MAX. They will operate at those max specs only momentarily, maybe when you turn everything on, otherwise consumption will be lower and possibly off by a large factor depending on the voltage of your power distribution and the efficiency of the adapter dong the conversion. If your output on the DC side is close to the max ratings, then you can assume on the input side you'll also be close to the max. If you want to figure out the worst-case-scenario, add up all the input specs of the adapters.
Look at the example I gave above. My LED driver can power 2.5A worth of LEDs at 12v, yet it's only going to consume up to 0.42 A at 90v on the supply (input) side.
You can't apply the numbers from the DC side to the AC side directly (alone) due to inefficiencies in power conversion inside the transformer. When you look at specs for other devices, you're probably looking at the AC numbers, such as on a toaster, anything with an AC motor, a lightbulb, etc. For anything with a transformer/driver you have to look at the input specs, not the output specs. To get accurate numbers you'll have to take actual measurements however. Use something like a Kill-A-Watt.
So let's see about some ballpark calculations based on my LED driver above operating at max load:
2.5A at 12v = 30 watts. 30 watts divided by 120 volts = .25 amps + waste.
If you want to figure out the efficiency based only on the numbers printed on the transformer/driver:
2.5A at 12v = 30 watts. 30 watts divided by 90 volts = .33 amps. .33 divided by .42 = .7936 or 80%
So now I can do this...
1.1A of actual LEDs on that driver at 12v = 13.2 watts. Divided by 120v is 0.11A plus 20% is 0.132A or 132 mA (that's about 15.84 watts if you want to compare consumption to an incandescent lightbulb).
If we were to assume that your LED driver/adapter were exactly the same...
6A LEDs @12v = 72 watts. Divided by 120v = 0.6A plus the 20% is 0.72A (86 watts). Take a look at the adapter specs to compare.
Obviously 120 is greater than 12v by a factor of 10 so the first two calculations aren't needed, just move the decimal place once to the left on the consumed amps of your LED load.
Buuuut. 120v is a nominal figure. Maybe your house is supplying 110 or 115 or 125, etc..
