Automated (DMX) Iris for generic profile

[Neil Hampson]

I am designing a show for Easter next year and one of the directors requirements is for an overhead profile spot, OK BUT this spot must appear to grow or shrink in size (The sow is the Children's Ballet of Alice in Wonderland) I really do not want to blow the budget on a moving head / scanner just to do this one effect, in one scene when all of the other parts of the show do not really need the added complexity of movers.

 

What I need is a DMX controlled Iris. I've had a quick look around the blue room and I can't seem to find anything, anyone have any ideas...

If I can't hire one I am prepared to have a go at making one,

I have:

1 Channel Demux (From Smoke M/c)

An Iris from a Prelude that I'm willing to butcher. (I am hoping that this will fit the gate of a S4 or an SL)

its of stock bar and shim steel

4 months.

 

What I don't have:

Motor or gearbox

Control gear for Motor in order to reliably stop the iris in the right place each time at a certain DMX level.

gearbox for reducing a 1500rpm motor to 10 cm of lateral movement for the Iris lever.

 

Just another question as this unit would be over the stage on the LX bar, should I be even thinking of making something like this myself, which in all probability end up looking like a mechano project.

 

Any help in this would be greatly appreciated.

Thanks in advance.

[Ike]

If you were going down the route of building one an RC servo springs to mind, the type used on radio controlled cars etc. They have inbuild electronics that use a pulse width modulated signal to set the position and deal with all the feedback etc themselves so all you would need to build is a simple voltage to PMW convertor and sort out the fixing and lever arangement.

 

HTH

 

Ike

 

EDIT: Just done a quick google and found http://www.active-robots.com/ who are selling servos for about £10 and also do other electronic/mechanical bits that might be usefull

[pritch]

To add to what Ike's already posted, Milford Instruments do a DMX / Servo board:

 

http://www.milinst.com/

[DavidLee]

I am designing a show for Easter next year and one of the directors requirements is for an overhead profile spot, OK BUT this spot must appear to grow or shrink in size...

 

What I need is a DMX controlled Iris.

Do you really? You have plenty of time to experiment so before getting complicated try the simple solutions first. Try hanging more than one lantern close together focussed on the same spot but with different beam angles. Cross fading from one to another will give the effect of a shrinking/expanding spot. Two lanterns may be enough but you could add as many as you have room and circuits to accomodate and make the effect as smooth as you like.

 

Also if you adjust your lamp focus to give a peaky field that will add to the effect of a shrinking spot as you reduce the intensity.

 

David

[GRisdale]

City Theatrical make a DMX controlled iris for S4s and SLs as part of their Autoyoke range. Never seen one - but I know they exist... Someone must have one in their hire stock. If you do decide to go down the Blue Peter road I've used the Millford instruments boards (as described above) and they work really well...

 

Gareth.

[ajh51]

A thought: - if you can arrange a dc motor drive for the iris and connect a linear travel potentiometer to the iris lever then you can probably use your demux to control it, although it would require some basic electronics. You'd effectively be making a dc servo such as are commonly used in industrial machines for remote position control.

 

Basically you'd put a fixed dc voltage across the potentiometer and then compare the voltage on the center tap to the voltage from the demux using a comparator. The output of which would drive a power transistor to control the voltage to the motor.

 

However I suspect the mechanical side of this will be a more of a pain.

 

Hope that is of some help...

 

Andy.

 

Edit: Beaten too it - an off the shelf solution looks a better bet ;o)

[Neil Hampson]

Thanks for all of the replies, my electronics theory is probably not as good as it used to be, but at least this at least gives me time to play. My first thought was to have four or five profiles with graduated beam angles 12" to 9' all on the same spot, however Lx 1 is always a crowded bar and without double hanging I didn't think I had the space, plus it's extra hire with the additional kit. My brother used to have a few R/C planes so I'm off to see him and see what we can do between us, as I suspect the city theatrical kit is expensive (if it's even in the UK as I think they are a US company)

 

Thanks for the Milford link, I feel a credit card spree coming on - so many projects hmmm.

 

By the way without having one in front of me is there anywhere on the web were I can find out the gate sizes of lanterns, generally if I'm luck I only find out the gobo size, but not the actaul gate size. (I need to know the sizes for a s4 zoom or an SL, if someone has a gobo holder and a ruler handy...)

 

Thanks again.

[Nick S]

I have a DMX controlled automated iris sitting on a Source 4. It runs off the same power supply as the Rosco I-cues, but I can't for the life of me remember the make/name. I shall take a look tonight if I can remember. The one huge problem is it has a tendency to make an extremely high pitched whine when nearly fully closed...

[robert_stemson]

I tried to hire a DMX iris for a S4 or SL but Stage electrics, Sparks and White light do not have the City Theatrical DMX Iris or similar in stock, so Instead I hired a Autoyoke which was offered at a exceeding good price (Stage).

 

I contacted City Theatrical about purchasing a DMX Iris but it would take 3-4 weeks from the states, plus it would cost £450! not including power supply! But I did find out who has purchased them recently, AFM! They might be worth contacting and asking nicely.

 

Another idea that might work, if you have an colour changer wheel or animation wheel + motor, why not use black wrap to create your iris sizes, focus the lens on the wheel to get a hard beam and rotate as necessary. Only problem is that you might not know what colour frame it might be in as it will be hard powered, and it wouldn't be a clean smooth action on stage...an idea.

 

Go onto the ETC website and download the S4 bundle of Information! Should/Might give you the size of the gate.

[bruce]

If taking the DIY route, perhaps consider car headlamp adjuster motors. Easily adjustable via a 12V analogue signal, so interfacing to a +10v supply would be straightforward, sealed unit with built in worm drive and linear output, and probably about an inch of travel.

 

Extortionately dear at the main dealers, costs pennies at the scrappy..

 

Guess which part of my car I've just been repairing...

[colourwatt]

It seems that the "moving light" use idea, has been ditched quite early on.

Other talents for moving light(s) are:- colour change

strobe effect

gobo projection + change

repositioning

quiet

OR how about using a manually controlled followspot.

[maeterlinck]

Sounds like a good project. If you do go ahead with this I'd be very interested to know how it goes. I spec'ed the Milinst DMX Servo Controller and a Servo from Active Robots for a shutter for a projector but we haven't built it yet...

I'd think that getting 10cm of travel from a 60deg servo would be easily achievable, I'd even think depending on how you attach the servo and actuator to the iris arm you would be able to do it without ruining a proper S4 iris.

 

Good luck!

 

OR how about using a manually controlled followspot.

Why manual? Go automated with a Robert Juliat Lancelot! :D

[Tomo]

Is there any reason why you've discounted a moving light?

 

The Source 4 Revolution has an iris module as do many other moving heads, both tungsten and discharge.

 

You may be able to replace several specials with a single moving head, depending on your design vision.

 

Otherwise, City Theatrical make DMX Irises for the Source 4 and Selecon Pacific - they need a generic scroller PSU which you can hire at the same time - and would also run a few scrollers if you're using them.

 

Whitelight definately have some, although they may not be willing to hire them separate from their Autoyokes.

 

Unfortunately I don't think there's any way of fitting a Wybron Eclipse II iris dowser into the gate, and you won't get a usable image from it at the normal gelframe mount point.

[johnhuson]

Before I start this rant I would like to say it's not aimed at anyone in particular, and is not entirely prompted by this thread. However there appears to be a common theme on this forum (particularly recently) that as soon as some one requests an idea to produce an effect that can be achieved more than adequately with a generic fixture(s), there is automatically a suggestion that because a moving light has this function, you should use one as it can do so many other things that you may not of initially thought of.

 

Fine in some cases this can be true, but just because a fixture can produce many different colours, many different patterns (gobo's) and can point at anywhere on your stage doesn't mean it can replace the job of all (or most of) the other specials in your show. Granted a strategically placed moving light can replace many other specials in a show, but what some people fail to remember is one of the fundamentals of lighting design....and that is direction. As an example a moving light positioned in the centre of a mid stage bar isn't a replacement for a special which needs to light downstage left from the front. Just because the light can hit there doesn't mean that it's from the correct direction.

 

This is one of the reason's that in the early days of moving lights in theatre (when it was very expensive!), many designers experimented with fixtures that not only could pan and tilt, but were also fitted to tracks so that they could traverse up/down stage or stage left/right to achieve the flexibility required. This never took off, mainly because moving light technology became more prolific and therefore became cheaper to have multiple fixtures covering all angles/directions, rather than expensive, noisy and un-reliable track systems.

 

Most professional designers will only consider moving lights for one of two main reasons. Firstly they require an effect that can only ever be produced by a 'moving light' i.e. you actually need beams of moving light or visible/rapid effect changes. This tends to occur more in concert and to a certain extent musical theatre productions. The second reason a designer will chose an automated fixture of some kind is it will quite clearly replace the functions of many existing fixtures in a design, this is more the norm in theatre. This decision tends to come further on in the design stage, rather than 'I'm doing this show, I need moving lights'.

 

Design is about looking at what needs to be achieved first, and then deciding/designing how to achieve it.

 

Anyway, rant over.....back on topic!

[JimWebber]

Before I start this rant I would like to say it's not aimed at anyone in particular, and is not entirely prompted by this thread. However there appears to be a common theme on this forum (particularly recently) that as soon as some one requests an idea to produce an effect that can be achieved more than adequately with a generic fixture(s), there is automatically a suggestion that because a moving light has this function, you should use one as it can do so many other things that you may not of initially thought of....

 

SNIP

Fully Agree with Mr. Huson above.

 

I've been sitting on this post for a little while now, but I too have noticed, (Not just here on the Blue Room) there appears to be a definite "I can use movers, how can I put them in my show?" attitude.

 

I personally have mainly used movers to replace many specials, and rarely for the fact that they move and generally "Look Cool".

 

People need to realise that all these toys are great, a tool used to achieve not just a vision, but a vision that is an integral part of a production.

 

Just because they are there, it doesn't mean they HAVE to be used. I am generalising here, but it does seem to be the younger generation (Cor I'm only 33 and I'm talking about the younger generation...) that falls into this trap.

 

Rant over

 

Jim