Why do some radio towers blink? (opens in new tab)

> This is best practice for anyone who uses three phase power.

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...

I was told that you want lights on all 3 phases so that you can see spinning things spin. If the lights are on single phase, they will dim 120 times a second, and the strobe effect can cause spinning things to appear stationary. With 3 phase, at least 1/3 of the lights are lit all the time.

At work we run a lot of machinery with motors and its obvious when phase loss happens. From my office I can tell if the lights go out/dim and the usual shop "hum" becomes a buzzing grunt that is immediately identifiable. Older machines have to be manually powered down but the machines I rebuilt have phase loss protection in the PLC thanks to a power monitoring terminal in the IO (Beckhoff EL3453.) Since the PLC is on 24V DC I have a capacitor backup module fronted by a 24V PSU that takes the 480V three phase power which tolerates a phase loss. The machine safely stops the process and shuts down the pumps and any other AC loads, then waits to be manually powered off as the PSU and DC side doesn't care.

Jeff, it's very cool to hear from you as I have enjoyed your videos for some time. I would like to make one request though. Next time you do a project like "How I almost broke MrBeast's Ages 1-100 video" that involves setting up interactive electronics for an event, you should really call me. I managed interactive technology deployments for the automotive marketing industry for over a decade. It's a niche that has unique challenges which you fell face first into. I would be happy to help make things go much smoother should you ever do something similar. Proof: https://imgur.com/a/5z5JrwT I'm also on Reddit, same screen name if you want to dm me there.

Phascinating

I couldn't help myself, downvote at will.

I imagine that a properly constructed ghillie suit covered with chain link fencing, barbed wire, no trespassing signs and a blinking red light might go undetected...

Seems to be needed only for old towers:

> 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?

That is one of those wonderful facts that's both interesting and in hindsight completely obvious.

Speaking of, I was recently looking into what exactly makes lights NVG compatible, and found this informative PDF: https://www.consolite.co.uk/wp-content/uploads/2017/05/Basic...

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

I never appreciated how realistic FS was until I started studying for the navigation part of my PPL. I flew a 172 too so the instruments felt very similar.

Lighthouses are usually white. They used to rotate (sweeping the beam) but tend to flash now I think. Nautical charts show the elevation of the light, the visibility ranges and the pattern of on/off (eg Fl (2) 10s 41m 17NM). Some lights are sector lights, so red/white/green depending on your position, they indicate if you are in the correct approach channel.

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)

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.

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.

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.)

That's what DCF77 is. Or GPS.

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.

> It's a transcript of the video at the top.

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).

Wow that wasn't clear to me either, thanks for pointing it out

Yes, reading transcripts is a terrible way of ingesting information in my opinion.

As far as I understand, non-US systems don’t always use (primary) radar.

I know. But when I was programming LEDs for my single board computer, I found that blinking the LEDs used a lot less power. If the blink rate was fast enough, your eye did not distinguish that from the LED being on 100% of the time.

I don't know if battery powered devices generally use that trick or not.