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Altman Comet Followspot dimmability?

Discussion in 'Lighting and Electrics' started by abalone99, Nov 18, 2008.

  1. abalone99

    abalone99 Member

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    I'm lighting a show at a middle school and using an Altman Comet Followspot. It will be run by a middle school student who has so far been very competant and I'm giving her lots of practice with the followspot but I'd like to reduce errors as much as possible by controling when it's on and off through the board. I noticed a note on the back though with all the other informatin that says it's not dimmable. This struck me as odd b/c I could have sworn I've controlled the same followspot in another show years ago. I just got done searching the internet up and down and wasn't able to find an answer to my question, so I'm coming to you good people. So, anyone know if I dreamed up that I can dim this followspot from the board? If I did, what's the reason behind not making the followspot dimmable? Does the lamp (360 W FLE) not like it or something? Thanks for any advice/info and especially for any concrete answers to my question.

    I'm also working with an old Electronics Diversified board w/o a name. I searched the internet again for a manual of some sort but didn't find a match. The closest console I can find that resembles it is an ED Lite. But my board has a more extensive LED display. I forgot to take pictures, but will hopefully be able to return with some later.
     
  2. Sony

    Sony Active Member

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    It's not dimmable because of the fan mounted in the base doesn't like to be run on low voltage and there isn't seperate plugs for the fan and the lamp like there would be on one that is dimmable.

    The best thing to do is to get a grease pencil and mark on the housing where the douser should be for the light level you want and then number them. Then give her the cues saying I want the light on such and such with the Rosco #04 Gel at intensity level #5 or something along those lines. If she is as competent as you say she is then this will be no problem for her!
     
  3. lightman02

    lightman02 Active Member

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    As far as the board goes if it has an LED strip on each of the cross faders then it's most likely a trabador plus console (something along that name). Does it have a key switch in the middle as well?? Also as far as the follow spot; the only way you could dim it is to rewire it which I would not recommend of course if it's not your, the gel idea would be best for now.
     
  4. church

    church Active Member

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    The comet is not dimmable because the lamp is run from a transformer - a regular dimmer does not work with a dimmer, which is designed for resistive loads where the voltage and current are in phase. With a transformer there is a phase difference between the voltage and current which must be addressed in the design of the dimmer circuit or by replacing the original transformer with an "electronic transformer". This is not something you can do at home without specialised engineering knowledge and invalidates the approvals on the equipment triggering the need to have local electrical approvals issued.
     
  5. lightman02

    lightman02 Active Member

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    My bad, you are right, I was thinking of the standard comet with the 1000watt lamp I forgot about the FLE lamp this model uses.
     
  6. renegadeblack

    renegadeblack Active Member

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    What about just plugging it into a channel and either having it at full intensity or not on? We have coves that we put our spotlights in and for some reason, someone decided that we didn't need an outlet on the upper level where the spot goes (not to mention that there isn't a light switch, but that's beside the point). I often use a stage pin to edison and plug it directly in and just leave the channel in because there are dimmer outlets up there. Is that safe? It hasnt caused issues thus far.
     
  7. gafftapegreenia

    gafftapegreenia CBMod CB Mods

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    So you are running your spot off a dimmer at full?

    What kind of spot are you using?

    This could be potential problematic, especially if the spot has an arc lamp, as the dirty voltage from a dimmer, even a dimmer parked at 100%, can have negative effects.

    If this is a permanent thing you might want to consider getting non-dim modules for the dimmer rack that would act as a standard, dmx controlled switch to turn that circuit on or off.
     
  8. renegadeblack

    renegadeblack Active Member

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    Yes, I'm running it at full.

    No, it's not something we do often, only when every other extension cord is missing or in use.

    Also, it isn't a carbon arc, atleast I'm fairly certain about that. It has a filament which illuminates. Also, the reason that we use it is because there isn't an outlet where the spotlight is. If we were going to install a DMX switch, then we'd just go and put an outlet up there instead. I have however, been preparing to ask for a DMX cable to be run from my light bar back to my booth in case we ever decide to use some moving fixtures because as of right now, we just have conventional fixtures. We did once use strobe lights that had a DMX connection option, but because we didn't have any DMX to run between the two of them, it wasn't synchronized :(
     
  9. icewolf08

    icewolf08 CBMod CB Mods

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    Lets just quickly clarify a few things. The Altman Comet, to which this whole thread is about (as we were told by [user]renegadeblack[/user]) uses a low voltage incandescent lamp and has a fan. Both of these are reasons why they don't love to be dimmed on a dimer. It is true that the spot would be an inductive load, but putting it on a dimmer left at full should be OK, the odds are in favor of nothing going wrong.

    Now, what [usr]gafftapegreenia[/user] was talking about in reference to relay modules. While they are like a DMX controlled switch, they sit in your dimmer rack in place of a dimmer. This allows you to have "pure" non-dimmed power coming out of a circuit, but you can turn it on and off from the board. So it would not require any extra DMX runs.

    As for syncing your strobes (which is a slight hijack), Running a data line between them doesn't always sync them. Many strobes get their pulse timing from the frequency of the line voltage (60Hz in the USA). However, if you had the strobes on two different phases the timing would be off, you may not actually be able to get them in perfect sync. Sure, using a hand controller and operator can also cause sync issues that could be solved by controlling from the board.
     
    Last edited: Nov 24, 2008
  10. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    Alex ([user]Icewof08[/user]) has paid Noah ([user]gafftapegreenia[/user]) either the nicest compliment:), or the worst insult:(; he'll receive today, by referring to him as Derek ([user]derekleffew[/user]).:rolleyes:

    Since I was dragged into this, I'll voice my opinion. ON/off DMX control from the console is not necessary. If we're speaking of ETC Sensorâ„¢ or Sensor+â„¢ dimmers, the choices are R20 modules (R stands for Relay) which provide for DMX control, or CC20 modules (CC stands for Constant Current) which are "always on" except by turning off the breaker, just like a wall convenience outlet. In this case, where a followspot operator will be at the fixture to turn it ON and off, there's no reason for remote control. The CC20 modules are less expensive, and more readily available (in the rental market). [Note yet another type of Sensor module, the Air Flow module, (not to be abbreviated as AF, so as to be confused with Advanced Features) is an empty tray for use when a rack is not fully-populated, and has no electrical connections.]

    If we're NOT talking about Sensor dimmers, just about any other manufacturer's modular dimmers (those that pull-out of the rack, usually in dual-module trays of two dimmers each) may be modified to become a "constant on" module, fairly simply, by a qualified individual; or available from the manufacturer. Having a few extra dimmer modules that have been modified and LABELED clearly as CONSTANT ON, comes in very handy when one needs to provide non-dimmed, non-regulated power to a location normally served by dimmers; to power 120V moving lights, scrollers, I-Cues, and other accessories.

    If lamp control from the console is desired, for a followspot that uses a 120V incandescent lamp, (and thus not the Comet, which uses an 82V lamp), the lamp may be isolated and plugged into a phase control dimmer, (though a Variac would work with the Comet's 82V transformer) but non-dim power must still be supplied for the fan(s). Modifications of this type must also be done by a qualified individual.

    Review the glossary; carbon arc is one of many subsets of discharge (arc) sources. None are electronically dimmable. Also, as we have illustrated, just because a source has an incandescent filament does not mean that it is dimmable with a modern SCR phase control dimmer. In a followspot, there are often motors (fans) and transformers involved.
     
    Last edited: Nov 23, 2008
  11. gafftapegreenia

    gafftapegreenia CBMod CB Mods

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    Thanks for the clarification derek. This question comes up a lot, might it be good to modify that for the wiki?
     

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