20kW Bulb Turns Night into Day | Hacker News Reader

20kW Bulb Turns Night into Day

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29 pointsbane11 comments

This may be a bit OT, but I feel like it's unfortunate that "watts" (i.e. power consumption) is the default unit used in lighting. It's like measuring the speed of a car in miles per gallon.

Seems like it's changing a bit after CFLs came out and they started putting luminosity outputs on the packaging, but I think people still mostly go by "incandescent watt equivalent".

Power = energy flow per unit time. So you can talk about radiation output, radiant flux as it's called in physics, in terms of watts: 683 lm of light at 555 nm wavelength equals 1 joules/second (=1 watt) in radiant flux[1]. 20 kW in light output would be about 14 megalumens.

[1] http://www.dfisica.ubi.pt/~hgil/fotometria/HandBook/ch07.htm...

Gallons per hour would be a better analogy.

You can get 12kW/18kW with ballast for cool ~$40k https://www.arri.com/lighting/m_series/products/arrimax_1812... Arri had, and Mole Richardson still has a 24kW version too. Here's an 18K burning insects: https://www.youtube.com/watch?v=74ub_bysnl0

Passing by one (a few meters away) feels like you could (and you probably could) grill a chicken in-front of it.

Can someone explain to me what's going on with the control panel? I see three round things and rotating things below that. What are those?

Also, isn't it dangerous to have that equipment indoors in a carpeted room? Obviously he probably knows what he's doing and so I would guess it's not that dangerous because of that, but still looks scary.

Finally, how do you get that amount of power in a house? does he have a special installation that provides more power that a regular house connection would?

I'll take a stab at this:

I see three round things and rotating things below that

It's some variation on this variable autotransformer: https://en.wikipedia.org/wiki/Autotransformer#Variable_autot...

that's a way to gradually increase voltage.

isn't it dangerous

I was also more than vaguely disturbed by how casually he was operating. That bulb perched on a stool didn't seem all that stable. But as you say, "he probably knows what he's doing".

how do you get that amount of power in a house?

"two hundred amp service" is very common in the USA. I just checked the breakers in my garage. My main breaker is labelled 200 Amps. It has two "poles". Which means there are two separate 120 Volt inputs (referenced to Neutral). The inputs are 180 degrees out of phase, so across them is 240 Volts. 240 * 200 = 48,000 watts.

Ah. It definitely looks similar to that. I also noticed that he would move the skull shaped lever up and down and that would change the rotation on the transformer so I guess it's also to show the power up process.

Yes, I was also thinking about that fragile thing leaning over and causing damage.

Aha... that explains it. I knew I was missing some math!

here's a video of him actually building the 20k watt power supply https://www.youtube.com/watch?v=Ka-LEcZaYqQ

should answer a few of your questions.

the "three round things" probably are controllable transformers to set the voltage.

At least the electrical equipment seems properly build and hooked up, so it should be fairly safe. I'd imagine the bulb breaking/falling over wouldn't be pretty through, and I would prefer that to be caged in and properly mounted...

At least here in Germany 20 kW is commonly available in a normal home power-connection. An electric water heater (for showers etc, not the electric-kettle type ;)) has 20 kW or more as well.

Yeah, I also was thinking about that think leaning over and then causing some damage.

I wonder how much uv it is generating.

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