bigclive

So, on the basis that orchestras are basically very, very loud and that the performers need to be able to hear their own instrument, what can one actually do? It's a bit like a DJ suing for hearing loss.

The answer here is to put a HUGE tub of earplugs on a shelf on the stage with a sign that says:-

 

Long term exposure to loud sound can cause hearing damage. We strongly recommend the use of earplugs to protect your hearing. You may prefer to invest in a personal pair of high quality noise attenuators as used in other areas of the music industry for better control of the sound without compromising artistic feedback.

Sorry, didn't realise it was an old thread that had been resurrected. I replied to one of the original comments and have deleted it now to avoid making things messy.

I don't think I've actually come across a truly water resilient moving head light that hasn't turned out to be quite as waterproof as hoped or has reliability issues with maintenance made somewhat more complicated by the attempt at waterproofing.

Note that many modern chasing strings with two wires actually have half the LEDs with opposite polarity and control them by reversing the polarity to the string with an H-bridge.

 

The reason the PSU is putting out 31V is to allow nice round multiples of 10 galliumm nitride LEDs in series. That way they can do sets with 50, 100, 200 LEDs etc.

It would help if we had a vague idea how big the mouse is?One assumes not life size, and also not big bird?

 

He's about 12 inches tall, but only from waist to head (he's got no lower half). Imagine Elmo sized. :)

 

I too think that the puppeteer should get their moment of fame in the curtain call. So how about adding some floppy legs and the puppeteer can do it Avenue-Q style and just be in full view.

Having been up above many ornate ceilings like this and observed the seemingly random looking mish-mash of wood I can understand why some might think it's just bodged together. But it's not. There's a solid wooden structure and then supporting struts and braces are taken from that down to the plaster frame itself where an array of laths support the structure evenly over its surface. It's certainly no more mish-mash than the clutter of wires and strips of metal that hold up the false ceiling that will be above many of your heads right now.

 

I don't think it's that uncommon for an additional decorative feature to occasionally fail, but this is the first time I've come across such a significant structural failure. I'm thinking that there's going to be a lot of inspecting going on, and possibly the addition of at least a few safety wires on the most vulnerable bits in a lot of old theatres after this incident. But I'm sure a technical investigation will be made into the exact cause of this incident. It should be quite interesting.

 

Contrary to other comments, trusses are not anchored into ornate plasterwork. Small holes will be made through the plaster and fixings will be made onto structural supports above that are rated or can be augmented to handle any extra weight imposed. This is where the laser plumbs come very handy for ensuring that a hole can be made just big enough to give a little clearance around the suspension wire.

 

In the bad old days there were full catalogues of ornate pre-manufactured plaster sections for interior use and carved stonework for exterior use. You started with a fairly plain building and then added on all your Gotham City extras onto the inside and outside. They still do this, but if you look at places like Las Vegas the very ornate buildings tend to be decorated with hollow fibreglass shells. These are supposed to be fire retarded, but a quick search on Google will reveal instances where ornate fibreglass claddings have been ignited by adjacent welding.

 

I dread to think of the cost of getting a dome reinstated. I honestly think that in a case where it's been damaged beyond reasonable repair then a new ceiling should be put in that is fundamentally modern materials with a little bit of extra flair to match the style of the rest of the building. Getting a company that does enforced historical restorations is just writing out a blank cheque to freeloaders.

 

PS: I like the fact that just as I posted the bit above I saw a Bluerooom advert from a company selling polyurethane mouldings.

Very neat. When I used PCB laminate for front panels myself I used the white screenprint on the front for the graphics. It's actually quite tough.

 

I'm squirming at that ultra-thin cutting line. No problem if you have a guillotine, but quite tricky to saw accurately. A channel routed out there would have made it a lot easier to cut or snap the panel into the two halves with little edge cleaning required.

 

But the design is progressing very nicely. Good job!

Oh good. So I'm not the only person that sticks silkscreen overlays onto bits of cardboard, polystyrene or foam and then stabs components through them to see how physical placement will look in real life.

You can get blank metal panels and seals, but I am designing PCB front and back panels. The panels will come on as a pair on a common PCB which will have to be sawn in half as that's a much cheaper manufacturing option.

 

Are you adding snap-apart routed channels in between the fascia PCBs? That would provide a much neater finish than having to physically saw a PCB in half. Most manufacturers will add routed channels anyway if you give the separate PCBs separate outlines.

 

Sawing PCB material is messy and tends to leave a rather rough edge, hence why most PCB material is chopped by guillotine or panelised as snap apart boards.

Which CAD package has the Gerber issue?

I had some batches of PCBs made with immersion gold and was not impressed by their solderability unless the whole PCB was buffed to a shine with a cloth before soldering.

 

My favourite finish is HASL (Hot Air Solder Levelling) and I usually choose lead based solder so that the boards always solder beautifully even when stored for a while.

 

And talking of ill conceived ROHS "lead free" type things, I was quite amused to see on a chips data sheet that the manufacturer marked it with one of two codes for either ROHS or green. Kind of fitting really, since the lead free solders are most certainly not green in terms of the amount of lead free failures that have gone to landfill. Not to mention the hazards associated with the aggressive lead-free solder fluxes.

Can I also suggest that the design be made using "Chunky Trax" technology with all tracks made at least 1mm thick to make the ultimate design more serviceable. If the schematic is fairly simple then the few links on a single sided PCB are a small price to pay for the extra serviceability of a single sided board. It does usually mean more manual routing though. I know the cost difference between single sided and double sided is minimal, but anyone who services PCBs knows the benefits of single over double when it comes to swapping out components or hacking.

 

I've never really understood PCB designs where the tracks were all the thinnest possible regardless of actual space on the PCB. The Elektor PCB designs used to be like that.

 

Moderation: Moved from a different topic to here

Just a thought... In the past I've used PCBs as front panels with suitable holes, slots and screen printing. Mine had blue solder resist and white text. It's easy to design them on the same PCB package and they can be done on the same panel.

The science of a lamp failing and taking out the triac is that when the filament breaks it sputters metal vapour which turns the lamp into an unballasted discharge lamp briefly, often turning the interior of the lamp a shiny black in the process as the metal vapour condenses on the glass.

 

The main thing is that it does effectively go short circuit, so the total circuit impedance/resistance is the only current limiting factor.

 

Fuse choice is important. A glass fuse is only designed to break a short circuit current of about 35A and current higher than this will result in a brief sustained arc in the fuse as it happily passes hundreds of amps. If the fuse has exploded or gone black inside, then this is what has happened. Sand filled ceramic fuses are rated to break over 1000A and will do so in a fast controlled manner. The FF fuses are expensive but probably easier to change than a triac. The quick-blow fuses will probably save a few triacs. The slow-blow fuses will not really save triacs.

 

Yes I know that the glass fuses are cheaper and you can see through them to check if they've gone boom, but seriously, you need to use ceramic fuses in mains circuits subject to high current faults.

 

Big fat chokes do indeed limit the current of a dead short enough to save robust semiconductors. They also limit the current of a wiring dead short, but lets not go there, it's scary. You might as well throw your breaker trip characteristics manual in the bin for a partially dimmed short circuit with a fat choke in line. The choke will get hot. The breaker will not trip in a hurry.

 

A BTA12 is a fairly lightly rated triac. A BTA16 would be better in the same package form, but a BTA26 or higher would be best, although the package is bigger and may not fit in some triac mounting arrangements. The peak current rating of these components is typically 10 times their normal rating, so using a high current triac gives a more significant short circuit current handling capability.

 

The snubberless triacs have a higher DVDT rating, which basically means they can handle sharp transients better then ordinary triacs. These transients could be from an inductive load, and in some cases can cause false triggering of the triac.

 

The best dimmers either use enormous indestructible switching devices like inverse parallel thyristor modules, or have easy to change triac assemblies so that changing a triac is almost as easy as changing a fuse.

One advantage of the LPG version with an external tank is that you could use an adjustable regulator to control the flame height. I didn't see a local accumulator in the unit, so it wouldn't perhaps have the same fireball spitting potential as some units. Good for jets of flame though.

 

I have seen externally run gas hose get ruptured and ignite though....

So it doesn't use gas but it monitors the pilot light with a UV sensor? Doesn't that suggest a gas powered pilot flame?

 

Hopefully it's not oil canisters pressurised internally with air, 'cos canned air and fuel in the right ratio is a bomb if there's flashback into the can. With the propane or butane cans there should be little to no oxygen present in the can. I'm not sure I know of any instances where anyone has had a can of air freshener detonate forcibly in their hand while spraying it too close to candles or cookers.

 

If it was a venturi system that drew oil up into a jet of air then that would be OK.

 

I think the LeMaitre coloured flame projectors use a glow plug to light the fuel. Their MSDS lists the fuel cans contents as propane 25-50%, butane 25-50% and isobutane 25-50%. Their coloured cans seem to use alcohol as a carrier for the flame colourant and probably inject a small quantity into the primary fuel.

 

BUT ANYWAY! Nice and simple isn't it? Probably frowned upon for use in a public area, but ideal for tech-dudes and their tech-buddies. And I think I can safely say that my can of air freshener is a lot cheaper and more readily available than even the highest profile brands of coloured flame fuel, and most likely a lot less toxic than a cigarette. It's also somewhat handier than a length of gas hose attached to a large tank of propane.

There's a very good chance that the "flame oil" is liquified gas loaded with a colour producing metal salt like strontium chloride, copper chloride, sodium chloride etc. The Chinese seem to like using the word "oil" to describe many things that aren't.

 

But by all means feel free to let rip with a tin of that oil and see if it evaporates briskly or lingers in a puddle. I've not actually sourced any in the UK myself yet.

Having recently bought one of these delightfully dodgy machines from China, I can explain why the original poster was just getting a small blue flame from the unit. He most likely used a standard butane lighter refill can. This fits and seals fine, but lacks the dip tube inside the can which is required to blow out enough gas volume to create a fireball or plume of flame. In his case the standard butane can just vented gas alone which was

of a low enough volume to mix with enough air to create a nice efficiently burning blue flame.

 

These machines use a DMX receiver board reminiscent of the type used in basic smoke machines, so there is no real safety system involved. However, they are very simple machines with basically a gas solenoid valve and ignition transformer wired in parallel so that whenever there's gas there's a spark to light it. I'd say that while the machines are not idiot proof by a long chalk, they are no worse than many bits of equipment used by the professional FX companies.

 

Back to the gas. Nobody would be foolish enough to put a can of aerosol air freshener in one of these things would they?

 

 

Oh wait! It appears I've done it and videoed the results.....

 

Next up WD40. But I won't be doing that indoors!