[rollulus]

Slightly off topic: typically, lights of neighboring towers blink asynchronously. But sometimes they are synchronized. Very satisfying. Anyone knows how this works? My best guess is e.g. DCF77. Thoughts?

[daemonologist]

I believe it's usually GPS/GNS (they all receive the time via GPS independently, and flash at predetermined times). The FAA requires synchronization for many classes of obstruction because it makes it clear that you're looking at obstruction lights rather than e.g. brake lights or traffic lights on the ground.

[geerlingguy]

Could they also use power grid sync? Not sure as I haven't talked to anyone in wind power, but grid sync would be pretty close to 1 Hz at least in the US.

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.

[askvictor]

My observation is not that they are sometimes synchronised, but some subset of the towers are synchronised (this was my observation in Melbourne AU). Upon asking reddit, it appears that it is the FAA-preferred option that all lights are synchronised: https://www.faa.gov/documentLibrary/media/Advisory_Circular/...

[SoftTalker]

I’ve driven through wind farms where the blinking tower lights are synchronized. Highly distracting.

[bluGill]

If you look close - almost impossible in the dark - you will see that most wind turbines don't have any lights at all. Too many lights is a distracion but all the synchronized lights are an easy to understand 'stay away from this whole area'.

There are FAA rules on this.

[rts_cts]

Driving through a massive wind farm at night is a trip since they all blink in unison. Having them all independently would look interesting but could rapidly descend into madness:

https://archive.org/details/bigclive_20230516

[scblock]

When it's on purpose it's typically done through GPS driven clocks. This is how wind farms manage it, where all towers are required to blink together.

[floatrock]

Yeah, I've seen it with windfarms. Always wondered why do they need to blink at the same time. The scale of the blink is pretty jarring at night (but also awe-some, in the same way any big enough infrastructure project inspires a kind of awe).

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.)

[asdefghyk]

One option - Maybe the blinking time is set to a INDEPENDENT? accurate time piece - ie Blink on the change of a second

[anyfoo]

That's what DCF77 is. Or GPS.

[winrid]

It's probably just a side effect of them being powered on at the same time or not?

[anyfoo]

If they don't sync to a common clock source, they won't stay in sync for long. Probably not even for a few minutes or so.

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.