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Not all LED lightbulbs are created equal. I've been watching some guy on Youtube do various teardowns and tests on various brands, and it's been enlightening. His channel is at http://www.youtube.com/user/electronupdate

Also, isn't the phrase "What you don't know, and no one will tell you" oxymoronic? I suppose "what you don't know, and only I will tell you" doesn't have the same ring to it.




It's fairly obvious, that you and the guy that runs the channel in question are witches... prepare to burn!

Seriously though, this is pretty cool... I am fairly surprised that there hasn't been a DC standard for lighting fixtures come into play yet... Which could be much more effective in terms of cost over time, and temperature control. Given the shear number of wall warts, and other fixtures common in the home, it would make sense for a more common interface for DC (especially low watt)... USB seems to be becoming that standard, but for lighting, and safety for internal wiring a new standard is probably needed (or an old one revisited).

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Given that nearly everything in a home uses AC-DC converters, I'm also really surprised that there isn't (that I know) a standard for a whole house DC jack that can supply common DC voltages, removing the necessity for all devices to have their own AC-DC transformers.

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The wires would be too big. You just can't send enough power at a low voltage. You'd need either lots of dedicated wires to each outlet, or a wire as big as a hose.

AC is nice because it's easy to convert to other voltages. With DC you'd need either the exact voltage - or a converter, and if you have a converter you might as well just go directly from AC.

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Seems like Power over Ethernet would be a pretty good standard to go with. Right now it's good for 25.5 watts at 44 volts. Wikipedia says some vendors have tweaked the standard to use more lines and get it up to 51 watts. To over-simplify, the higher the voltage the less loss there is on the wire for a given amount of energy (amps).

Added bonus you get ethernet too so any devices like LED lights, cameras, etc can be programmable without wifi/zigbee/etc.

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Power over Ethernet only helps for not having to run a second pair of wires.

You would still need a DC/DC converter, and if you do that you might as well just go from AC.

PoE is helpful certainly, but not as a way of having universal DC in the house.

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You would still need a DC/DC converter, and if you do that you might as well just go from AC.

You are thinking wall-wart type applications. I'm more along the lines of infrastructure, lights and other permanently installed devices that can be designed from the ground-up to operate at 44v.

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> designed from the ground-up to operate at 44v.

Why? What's the benefit over 110v?

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Maybe not, but you could certainly replace recessed canisters, or other fixtures with those that have AC/DC power supplies built in, in such a way that they can have a larger surface in the ceiling/walls or even in the fixture that can then not be part of the "bulb", and subject to the same size constraints.

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A universal DC standard isn't a silver bullet. Different circuits/devices and different batteries require different voltages, so there are still conversion steps to go through. Not so long ago when linear regulators (which tend to be better at producing heat than desired voltages) were typical, this would have just meant another wall wart for most devices. Even now, it still means some added cost, complexity, size, and weight.

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There was that one video about a guy who built a solar-powered house off-grid which uses DC to power anything. I believe he used several wires which he could combine for different voltages. Let me look if I can find it.

edit: Here it is: http://www.youtube.com/watch?v=m5rM7QDi_5E&t=11m39s

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Low-voltage at any meaningful distance is extremely lossy. Unless he's using big expensive wires, he's going to have a lot of voltage drop on any load beyond a small gadget. Even just pulling, say, 50 watts out of a 12-volt socket with a 20-foot run of 12 AWG behind it gives you a voltage drop of over 2% at the socket. At 120V/12AWG, the drop would be 0.22%. You'd have to use ~2AWG to match that. That's a lot of copper.

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Also, isn't the phrase "What you don't know, and no one will tell you" oxymoronic? I suppose "what you don't know, and only I will tell you" doesn't have the same ring to it.

It's a cheap trick of appearing honest by using impossible hyperbole. The meaning of the statement is so obviously not equal to its literal meaning that if the writer is challenged over the honesty of it he could plausibly defend it by saying, "It feels like this fact is not being communicated sufficiently to consumers who are not familiar with LED lighting." In other words, it's a way to manufacture compelling copy without needing any facts to back it up.

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Well there goes my day... Thanks for posting that link!

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While you're at it:

http://www.youtube.com/user/bkraz333

http://www.youtube.com/user/eevblog

http://www.youtube.com/user/Afrotechmods

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"What you don't know" refers to the present moment.

"And no one will tell you" also seals it for the future.

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Sorry, I should have elaborated. It's oxymoronic when it's the title of a paper which entire purpose is to tell you what it just said no one would ever tell you.

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