Outdoor lighting

[sunray]

I saw the installation in the Sony Centre in Berlin yesterday where a dozen moving head units are mounted on top of 3 or 4 metre vertical truss sections. Each unit is enclosed in an inflated plastic enclosure. First time I've seen them, very effective.

[indyld]

You can get a whole crew member inside one. Apparently. Ahem.

 

They have an interesting feature that cuts power to the fixture if the dome loses pressure.

 

They are also blimmin' cumbersome and awkward to deal with. :-)

[sandall]

In a certain Edinburgh location the main villain is the Haar. A very dense sea fog that can penetrate where mere rain cant and results in water on ALL surfaces it can reach. It trumps horizontal driving rain for the amount of issues it causes.

The Haar isn't salty - just very penetrating. You could literally have a bucket upside down and there would be water on all of its inside surfaces.

My sister lived near Aberdeen, so I heard all about the Haar!! Down here we just call it fog. I assume that all the fittings get thoroughly coated with condensation inside & out overnight, but dry out internally during the day.

 

I don't know about radio but in TV, where Klystrons were used in the output stage, the Anode was nominally at ground with the cathode some tens of kV negative wrt ground. Water cooling of the anode using distilled water (actually, technically, I think it's de-ionised water) was done but this meant the potential across the cooling system was only a few volts

Back in the days when you could just walk up to the front door & say "we work for the BBC, can we have a look round?" I was given a tour of one of the Overseas Service SW transmitter stations (with great big glass valves) & remember being very impressed by glass tubes of water with several kV across them in the output stages of the 250kW senders.

[sunray]

You can get a whole crew member inside one.  Apparently. Ahem.They have an interesting feature that cuts power to the fixture if the dome loses pressure. They are also blimmin' cumbersome and awkward to deal with.  :-)

I did think they looked unnecessarily big for the application but knowing what shape moving mirror units are and allowing for heavy rain etc it started making sense.

 

I thought they looked like a simple option, I imagined they are a base with fan(s) and a collar holding the bag but I've not got close to them to get any idea how easy to use.

 

Ah but did the crew member stay dry and could he still drink his beer?

[Brian]

When I walked past the Natural History Museum ice rink the other day I noticed that had rain covers on the movers which looked like this...

 

[adam2]

Unlike distilled water, which was (is?) used for cooling the anodes of high-power radio transmitters - tens of kV across a column of water!

 

I don't know about radio but in TV, where Klystrons were used in the output stage, the Anode was nominally at ground with the cathode some tens of kV negative wrt ground. Water cooling of the anode using distilled water (actually, technically, I think it's de-ionised water) was done but this meant the potential across the cooling system was only a few volts.

 

 

Brian

(ex-transmitter engineer)

 

Yes.

 

Several different systems were used for water cooling high power valves.

 

One system was indeed to have the anode at about ground potential, ordinary tap water could be used and run to waste or re-used without much in the way of special precautions.

 

Another alternative was to use ordinary tap water, with a high voltage on the anodes. This required relatively long and very well insulated discharge pipes for the used cooling water. Glass pipes were common and the used cooling water was passed through an earthed metal grating before going the drain.

 

In yet another system, purified water was used, but was not consumed or run to waste. The water was boiled by the waste heat, condensed in a radiator or condenser, and returned by gravity. The only water lost was minor leakages.

 

Note that it was not usual to use purified water if this was continually run to waste, the cost of treating the water would be excessive. Tap water was common, if cheap and plentiful it could simply be put down the drain afterwards. If water was scarce or expensive, it was recirculated with a pump to/from a cistern. To prevent the water getting steadily warmer, it was common to use it for WC flushing or as the supply for a water heater. I worked on such a system that used water cooled valves for high power spot welding machines.

 

 

 

 

 

[bigclive]

My sister lived near Aberdeen, so I heard all about the Haar!! Down here we just call it fog. I assume that all the fittings get thoroughly coated with condensation inside & out overnight, but dry out internally during the day.

 

The Haar far exceeds normal fog. It's very much its own "thang" and is despicable for its ability to transfer massive quantities of liquid to the most protected areas. You can literally stand on the Tattoo gantry in the Haar and see water droplets running down metalwork that is completely covered and inaccessible to even the most violent storm. We leave equipment running 24/7 and just deal with it when a Haar happens. It requires a gentler startup sequence and some swapping of fixtures that succumbed to its villainous deeds. Typically during a run of the show we might experience on average of two Haars and since there's nothing we can do about it other than design the rig to be "Haar compliant" we just deal with it when it happens.

 

A good example of a particularly sinister Haar incident is when it finds its way into a well protected Socapex fan-out and takes down a bank of PRG Best Boys. Without the benefit of the 24/7 airflow the Haar then sets about one particular bit. The Pan/tilt yoke driver. The light has a fan that directs air onto the PCB and tends to build up fluff around certain critical chips and without the fan running that fluff then gets drenched in the permeating moisture of the Haar and takes out the card temporarily resulting in a string of canbus errors. The fix is to clean off the fluff and drench it in PCB cleaner to drive the Haar back out again, and the light then kicks back into action.

 

The PRG lights are just a dream to work with, but NOTHING can escape the Haar. (Hence why we only used Martin fixtures on the job ONCE and spent quite a lot of time changing lamp ballasts.) Even the veteran VL3000's weren't completely Haar-proof and their ballasts aren't exactly a treat to swap out. The vintage VL5's on the other hand were just ridiculously Haar-proof even when fully exposed to the elements, parked correctly overnight and started in a special dry-out cue. Seriously, the VL5's were "military grade".

 

I saw the installation in the Sony Centre in Berlin yesterday where a dozen moving head units are mounted on top of 3 or 4 metre vertical truss sections. Each unit is enclosed in an inflated plastic enclosure. First time I've seen them, very effective.

The inflatable domes are very good but come with their own problems, particularly when used with high power lights. The airflow in the dome itself tends to take a shortcut from the intake to the outlet and doesn't really stir it up inside. Some have strategically placed holes in the side to encourage more thorough airflow, but others just cook the lights and cause them to cycle thermally.

The vane switches that turn off the light if the airflow stops are notoriously prone to false triggering in strong buffeting winds and will douse a fixture repeatedly. The battery backup of the cooling fan is a great idea, but the SLA batteries used in them died years ago and nobody seems to gives a ###### about that. And the velcro on the domes is NOT bear-proof....