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This is absolutely untrue. You may be safer from shocks, but it's a much _worse_ fire hazard. The currents need to be higher at lower voltages. Higher voltages need less current for the same power, decreasing the fire risk.
If it means less time spent in a mess of wires trying to figure out which adapter brick is squealing, I'm all for it.
But please, please, PLEASE design a better connector than fragile USB-C. 120VAC plugs e.g. standard IEC computer power plugs can be hit with bricks and rammed into furniture while they are plugged in and they won't get damaged. All forces of impact get transferred to the chassis, not the PCB. That's good design. I break about a USB-C cable a week because they just aren't designed for the ruggedness that consumer use…
I don’t know… that seems excessive, even people I’ve known to handle all of their stuff like it’s free have managed to go mostly through 1-2 cables a year.
An LED doesn't run on 24V DC, what's the difference in efficiency between an LED lamp that runs off 120V AC and one that runs off 24V DC?
> An LED doesn't run on 24V DC It can. Cree's JR5050 24‐V LEDs run on 24V. They have 30V and 36V versions as well.
> AC won, mainly because of its higher efficiency when transported over long distances.
AC is not actually more efficient at long distance transmission, it’s less efficient due to the skin effect. AC is just easier to convert.
Earlier quoted context omitted.
But please, please, PLEASE design a better connector than fragile USB-C. 120VAC plugs e.g. standard IEC computer power plugs can be hit with bricks and rammed into furniture while they are plugged in and they won't get damaged. All forces of impact get transferred to the chassis, not the PCB. That's good design. I break about a USB-C cable a week because they just aren't designed for the ruggedness that consumer use…
> I break about a USB-C cable a week I don’t know… that seems excessive, even people I’ve known to handle all of their stuff like it’s free have managed to go mostly through 1-2 cables a year.
Reality is if you go out at all you've probably figured out that phones only come with 1/2 day of real battery life (because they do the damn factory tests with full bars of reception, not real world 1-bar reception), and you needed to charge a phone stuffed in one pocket with a battery in the other pocket, connected by a USB-C cable, and bike, ski, run, hike, climb rocks, whatever it is. Or had to use a laptop in a bus where an asshole plops their heavy ass next to you and you accidentally ram your laptop and USB-C connector into the side wall. Or because pants are designed with only 2 instead of 3 front pockets, one is occupied by wallet and another by a big fat keyring, you have no cohice but to put phone in your back pocket and battery in the other back pocket with a wire between the two and sit on it while plugged in. Or had to stuff your charging phone and battery into a jacket, crumple the whole thing and stuff it into a TSA bin. Or children bite your cables. Or dogs. Or the phone was in the car with a suction cup holder and fell off ramming its USB-C cable into some hard part of the car floor. THIS is daily consumer life.
If one hasn't experienced the above, they probably sit in an office all day and work out in a gym and are oblivious to the realities of active lifestyles and how they are highly incompatible with physically weak connectors like USB-C.
There is a line that’s incorrect in the article: > AC won, mainly because of its higher efficiency when transported over long distances. AC is not actually more efficient at long distance transmission, it’s less efficient due to the skin effect. AC is just easier to convert.
There is a line that’s incorrect in the article: > AC won, mainly because of its higher efficiency when transported over long distances. AC is not actually more efficient at long distance transmission, it’s less efficient due to the skin effect. AC is just easier to convert.
One reason DC power is more viable nowadays is (as others here have mentioned) the use of DC-DC converters. They internally actually use AC to do the conversion (usually at much higher frequency to save weight and cost on inductive elements). But they're not super cheap (not cheaper than transformers) and they can also be inefficient.
But part of my problem with this article is it kind of sandbags the efficiency. We can get pretty high efficiency inverters and rectifiers. >90% is common and 95-98% is feasible (and not uncommon). Low voltage DC (like 12V) requires MUCH thicker cables for the same power, which means a lot more copper (and copper mining). Typical line voltage can be very lightweight.
With DC, nothing is really at the same voltage, so you need DC-DC converters all over anyway, so you're not saving anything (although not losing much, either!).
Another important thing that really drives some of the advantages is: breakers, relays, and (much less important) current measurements of existing cables. All these are feasible for both DC and AC, but cheaper and easier with AC. AC is self-extinguishing as it crosses zero 120 times a second. That means you can switch a circuit on or off when the applied voltage is very low, meaning you can use cheaper and lighter power electronics. Plus, at a given voltage, there's a safety advantage as arcs will more easily stop with AC.
I actually think it's funny to see this in a "low tech" blog. DC ubiquity is something really only practical for significant use (i.e. beyond automotive or RV) with modern 21st century power electronics.