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Hybrid firing of effects and pyro


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A discussion on facebook prompted someone to suggest I "might want to discuss the issues with Mr. Parkhouse" - it arose from a discussion where someone (in another theatre, not mine) had a problem where the "ghost" DMX emitted when the lighting desk was turned was firing a confetti cannon (controlled by a solenoid vale) in the theatre. I suggested that in a situation like this the DMX shouldn't be the primary source of firing, but that if it was operating a circuit downstream of a key isolator, circuit selector and manual firing button (effectively a dead man's handle) with a dedicated operator checking for safe area so that the DMX was only fine tuning the firing time in a narrow window (the time the firing button was depressed) this would be a safer way of working, as the person on the controls wouldn't enable firing if it was not safe to do so. He argued that under no circumstances whatsoever should DMX ever be involved in any way, shape or form in the firing procedure for an effect (or pyro).


My argument is that without the all the manual firing controls being armed, it doesn't matter what the DMX does, it can't do anything. If the DMX does something strange during the narrow window that everything is enabled, the worst that happens is that the effect either doesn't happen, or happens at a different time of the window, a bit like the manual fire being pushed at a slightly different time.



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It's all down to risk assessment, and managing the risks you've identified


Personally, I'd be happy using DMX as a trigger if there was a keyswitch isolator and as many deadman handles as required to ensure safety of the effect (dependent on sightlines etc). These deadman handles should be setup so as only to enable the effect due to be fired.


A setup like this is conceptually not dissimilar to an operator pressing the red button on verbal cue from a DSM or showcaller.

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I think we have to accept with the advent of more and more synchronised and sophisticated 'show control and automated programmes' that "remote and secondary cueing" protocols will be needed and used... be that DMX or any other.


The question/statement made on the post seems to be offering an answer also but I would add my personal view that "Direct DMX control of (in particular) pyrotechnic effects should be avoided **" but there should be scope to take a cue from (say) a dedicated DMX channel.


The control system of the effect is where the cleverness should be focused.



The pyro control system and operator should maintain total control at all times and the responsible (dare I say competent) person be able to (at the last possible moment) temporarily switch over to receiving a remote trigger. This switching over process having the ability to be 'locked out' should the system detect anything present on the trigger line.


The reality of this sounds, to me, like people not having the means to have a dedicated/responsible person at the true energy source of the pyro control. This also would also suggest and take away the considered best practice of the operator being as close to the devices as possible during operation to ensure no last minute issues (moved, knocked, covered etc) and also to offer and demonstrate confidence to the performers.


I cite people like Disney for automated/synchronised events whereby their performers (may) have pressure matts to stand on and grip handles they must hold to complete and make the circuit before the cue is fired thereby ensuring (a little more) risk mitigation.


There are many remote controlled systems out there now but the ones of worth will always be the ones that default to 'no-fire' every time.




(Mr Parkhouse!)


** without secondary safety switching.

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That was my feeling, too, but I'd welcome further discussion.


I wouldn't be happy with the system that was originally described (where the only control over the solenoid was DMX) for exactly the reasons the original poster saw, but having multiple interlocks and a dedicated spotter who enables the effect for a short window while safe to do so I'd be happy with. The DMX control is for when you want an effect (and if could be a pyro too) to be synchronised with lighting or media events.


As an aside, I wouldn't have been at all happy with leaving the effects armed but unattended, but that's another discussion entirely.


EDIT - while I was replying to Jonathan Lincoln replied too:


My argument to the poster on FB was essentially what you've described, Lincoln, that the DMX is used as a trigger but it isn't the primary source of switching and there is a responsible operator ensuring at all times that it is safe to fire the effect. It also sounds, from the original FB post, as if the primary problem that led to the confetti cannon being left armed and directly controlled by the desk and misfiring was, indeed, a lack of staffing.

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DMX lets you fit the cue timing into the programme on the lighting desk, but unassisted it leaves you the obvious spurious DMX frames that cause problems. Having additional safeties like pressure pads, grip switches, and real live operators with a dead man's handle like device make things safer. HOWEVER if you put things on the DMX line that are specifically specified against then at least you should ensure that any possible failure is safe by safety distance but you can't stop the audience seeing an unintended pyro effect.
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I have been looking at some DMX controlled confetti canons, and was quite surprised that I could only find one that had a separate DMX safety channel.


A lot of these are really just blowers though, they are not confetti cannons in the traditional sense of a big bang and lots of confetti. Anything with a rapid release (compressed air or pyro) ought to have a separate non-DMX interlock in my opinion. Even a separate safety channel could be defeated by errors on the DMX.

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I asked the Facebook person how he felt about the Le Maitre Salamander. He said he would never use it's DMX interface.


Interesting, you would have thought Le Maitre of all companies would be ensuring the safety of their products.


From the manual, there are a number of safety features they have put into the DMX:

You have to hold the "safety" channel at 100% for 10 seconds before the fire channel becomes active.

There is a "DMX filter" which sounds like it needs to receive an identical packet 3 times before it is accepted. It says this adds 75ms delay to the DMX activation. You can disable the filter but they say "Warning: If the Salamander is operated with the DMX filter disabled, the manufacturer will not be held responsible for any unexpected behaviour under DMX control." - so they have clearly got concerns about DMX errors.


But the blurb also says "The Salamander is controlled by instruction from the DMX-512 protocol. The manufacturer cannot be held responsible for incorrect application or malfunction of data sent via DMX. Should DMX isolation or other devices be required for safe operation, this will be deemed the responsibility of the operator."

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Quite, Tim, that was my thought. Le Maitre have clearly put some thought into it, although a misfire could still happen.


The thing is, if you used a manual firing method instead, it's still possible for a misfire. The RA should take that into account, though, and mitigation should be part and parcel of using the effect (like any effect, pyro or not).

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Having joined the FB group so that I could read the topic, it strikes me that this isn't about using DMX to control air effects/pyro/flames/etc but about a venue trying to do things on the cheap and not having control over its staff.


The walk to the cannons to unplug them is round about and requires that you cross the entire theatre. This is something the crew would be unwilling to do.


Simple answer. Sack them.

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