A machine shop should connect 1/3 of their lights to each phase so it is immediately obvious if a phase gets dropped. Lots of equipment will suffer on two of three phases but with lower performance or even damage.
No, it’s not. It’s a neat trick that visually reveals when the utility drops a phase, but there are better ways to handle avoiding equipment damage.
Best practice is to use phase monitoring relays that can de-energize a motor when a phase is dropped/reversed to prevent damage. The trip time is adjustable and it’s more reliable than manually hitting an e-stop. It also won’t let a motor with incorrect phasing start up either. You see phase loss relays on a lot of compressor motors and other large motors.
Here’s a flyer for an Eaton product: https://www.eaton.com/content/dam/eaton/products/industrialc...
It's way less of a problem with modern machinery, and leds will blink in uncorrelated phases in a frequency that is different from the grid's anyway.
How does one connect a lamp to 3-phase power?
Are/were there 3-phase fluorescent tubes available?
Or are we relying on the spinny-thing that is to be observed to somehow be illuminated by all three phases, with three lamps or fixtures, simultaneously? Without such malarcky as shadows or inverse-square to muddy our vision?
Or maybe a multiplicity of single fixtures with 3 tubes -- one tube per each phase?
And even then: Doesn't it still strobe somewhat at (50*3*2)=300 or (60*3*2)=360Hz, instead of the 100- or 120-Hz that a shop lit by a single phase might provide?
(LEDs are out-of-scope of this question, of course: Line-voltage LED lamps can have integrated electronics and can therefore have diode elements that are driven by things that approach [or even achieve] DC, which changes the rules.
And, of course: Incandescent lamps have enough persistence that stroboscopic effects are generally not an issue with a human eye.)
It's a quick way to know if something is down, using context clues that are already there to begin with!
> Jeff: A full ghillie suit? Or I don't know what they're called.
If you see someone up in a tall tower wearing a ghillie suit [0]... that sounds like time to call emergency services while avoiding their line-of-sight. :p
(Perhaps they meant "Hazmat" [1])
My first thought would be “that might be the dumbest sniper I have ever seen”…while I was taking cover, because even if they are dumb, they might still be a capable marksman.
> Tower painting has changed a lot over the years. The older towers have lead in them. So whenever there's a project on the tower, it's not unusual to see the guys in some kind of a, what do they call those?
https://www.faa.gov/sites/faa.gov/files/airports/engineering...
tl;dr NVGs are sensitive to near IR so you want lights that are dim in those wavelengths (but not completely out since you still want to see them with NVGs) while still being bright in visible light. There's a neat picture of the flying controll tower on one of the UK's Queen Elizabeth-class aircraft carriers that shows two rooms with similar illumination levels in visible light, but under NVGs one room which isn't NVG compatible is massively brighter than the other. In the NVG-compatible room there were still a handful of panel indicator lights that were not compatible and lit up the whole space
Lights on towers mean stuff, especially to airplanes.
Lights are required for tall towers, and get this, towers next to airports.
You can guess how tall a tower is by looking at the lights.
It can be really confusing approaching a port at night. Never mind the city lights behind, and the cars driving about. 20+ lights flashing at different rates in the dark, some of them disappearing for seconds at a time. Oh, and if you turn your light on to refer to the chart, there goes your night vision!
Boat masts above 25m also have blinking red lights for the low flying aircraft (I guess its a bragging point)
Building a product that would sync at 1 Hz via GPS that works in the US and other countries with 50 Hz power would be a little easier than syncing to grid phase though.
You need an external, dedicated channel for this. You either synchronize with signals sent between towers or with a global signal from somewhere else (space). GPS broadcasts atomic time references for free, so everyone just uses that
For wind farm use most also have an external input for ADLS triggers, though that usually also requires a separate controller and communications connection to manage the ADLS signals.
The flashing red lights are L-864 type. The requirements are 20 to 40 flashes per minute (FPM), and typically 30 FPM is used.
There are FAA rules on this.
Wind farms have a certain amount of nimbyism because they "spoil the natural landscape." (So do regular farms -- nothing natural about grain silos or row crops, but that's a side topic...) Anyways, having that many towers blink in unison across that big a landscape is a weird effect when you first see it. I think there's an argument that if they blinked independently it would feel more natural in a way.
But since the blinking is all FAA requirements, I assume it's to help identify all the individual towers from the air. I suppose if they were all blinking independently, it would be a predator-trying-to-focus-on-a-single-zebra-in-the-herd problem, except in this case the predator is a pilot trying not to crash into a turbine.
Sure would emit more subtle 'part of the landscape' vibes though.
(Which I guess is exactly what you don't want when you're flying above them. Sigh.)
https://www.airporttech.tc.faa.gov/DesktopModules/EasyDNNNew...
As to community impact, radar-activated lighting is an approach that is being used in places this is a concern. It allows the lights to remain off unless there is a plane within the envelope that requires the lights to activate. It's expensive though.
presumably this makes it more striking, and thus easier to notice and avoid
You'd get the same phenomenon that you see when operating turn signals in traffic. They seem to weave "in and out" of sync. The frequency at which that happens is the beat frequency, i.e. the difference between the two blinking frequencies.
If you have shared line power you can just use that and everything will be locked in sync forever.
If you don't want to use that or radio, and you are outside, you could try to be really clever am sync your flash phases to a specific position of the sun. This is what the Long Now clock does. It'll be a different time each day, but it'll be the same for all units, within a small tolerance.
But presumably these lights at least have battery backup, given the obvious risks in case all of them were to fail at the same time due to a grid issue.
TLDR; White lights are used during the daytime, red lights at night (less annoying), towers under 200 feet don't need blinking lights.
Which is not obvious at all if you have JavaScript disabled by default, since it only shows up as a blank space, which could also be a blocked ad or an image which failed to load correctly.
The first few times I saw one of these transcripts with video at the top (IIRC, it was on Practical Engineering, not this site), I thought it sounded odd but didn't get that it was a transcript. Only later did I find out that there were videos (and they're great).
see https://www.ecfr.gov/current/title-14/chapter-I/subchapter-E...
I live near an airfield and the runway has flashing white lights at night to help guide the aircraft's.
They are not uncommon in Norway.
If you go to one of our major airports you will see one on the tower. The blinking lights also sit on wind turbines and TV masts, and anything taller than 15 meters in rural areas or 30 meters in populated areas will have some kind of light on it, sometimes blinking, either red or white.
https://www.jeffgeerling.com/blog/2024/what-happens-when-you...
I don't know if battery powered devices generally use that trick or not.
