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Mirror Ball Motor from Dimmer pack???

Discussion in 'Lighting and Electrics' started by who_touched_the_patch, May 3, 2005.

  1. who_touched_the_patch

    who_touched_the_patch Member

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    Location:
    Sydney, Australia
    I've got a lighting gig for this theatre company, and I've been presented with a problem I don't know the answer to.

    There's a mirror ball invloved, sitting above centre stage, with 2 par cans lighting it. There's no problem with lighting the Par cans, but the mirror ball motor is a problem.

    There's no 240v power point on the grid at that point, and it obviously needs to be switched on and off at certain points throughout the show.

    I was wondering if it was possible to plug the mirror ball motor from a dimmer pack and using a 0-fade time to turn it on and off. (0% - 100%) but I'm not really sure about doing this.

    Any comments? Suggestions?


    PS: Control will be from ESPII FX fader.
     
  2. eamon

    eamon Member

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    Hi

    Yes, you can "run" a mirror ball motor off a dimmer. The control desk should not not matter in this sense. The quality of the dimmer is the more pertinent.
    In order to run a mirror ball off a dimmer, you should use the dimmer as a switch/non-dim i.e. it has a trigger rate of xx% on the control desk and you are snapping the power on as opposed to dimming it. You can normally create this setting on the desk or the dimmer. The only problem I have found is that most cheap dimmers have a trickle and can(and have) triggered the mirror ball without you doing anything!!
    Sometimes you may have to place a load lamp(ghost load) on the same dimmer to solve this

    Hope this helps

    eamon
     
  3. ship

    ship Senior Team Emeritus Premium Member

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    Depends upon the dimmer manufacturer and mirror ball motor.

    Sometimes like on a Sensor rack, you can swap cards for a on/off switch to replace the dimmer. Otherwise and as a good point, depending upon the dimmer, the trim setting voltage at zero or 100%could be possible to cause problems with the motor of the mirror ball motor, used as a switch or not, if not it's chopped sinwave and lag causing damage.

    I take it for granted there is no way to hot patch channels and use if necessary a breaker on the hot patch circuit to turn it on or off without the power coming from a dimmer module.

    Most dimmer manuals say not to run power tools off a dimmer. Not good for motor or dimmer.

    On the other hand, somtimes it will cause no problems at all in the motor and if the dimmer is large enough and quality, no noticable damage in it's limited use. Done it before without a problem, but it depends upon the brand of mirror ball motor.

    Remember that most dimmers will be trimmed so that they have a lamp warming current on the lamps. This means that even at 0%, there is still say 7 to 20 volts going to the lamp in warming the filament. Depending upon the mirror ball motor power, it might not be enough to recieve this voltage because normally it takes 75 volts to get the warming current - thus the ghost load. On the other hand, who knows if it would or not in that warming current not being enough to spin the motor at full speed but it's current being there still in melting down the motor.

    Should call the manufacturer of the mirror ball motor and ask. They no doubt will know their product and have come across this problem before.

    Don't know if they are in Europe but in the US View-Mor http://www.vue-more.com makes a mirror ball motor that does not seem to have problems even being dimmed by a dimmer - linear or electronic. Good beefy motors for the 24" to 48" size mirror balls.

    Another option would I recommend would be to use one of the new American DJ DMX mirror ball motors. Believe it or not, they are very substantial in quality. Though I do have two out of six that might or might not be working after a tour in my repair pile. This way you can put the dimmer on at full, adjust it's trim for full voltage, and switch on and off the mirror ball motor, reverse or dim it by way of a DMX channel. That's I believe part of the design intent. Good design though we have two our electronics department in doing this, came up with years before in concept. This given American DJ has a 240v version as they probably do.

    Other things to do or check on the mirror ball motor. Unless running a 8" mirror ball, you should ensure the mirror ball motor has a slip gear so once it's powered off, the mirror ball won't damage the motor as it continues to spin.

    Also if it's using a key ring to hold the load, remove it and replace it with a 1/16" wire rope and nicopress sleeve so there is no chance that should the mirror ball get hit, it will fall.

    Finally, most mirror ball frames are cast aluminum and on larger mirror balls, them holding the weight of the mirror ball - given it's designed to hold that size in the first place, needs all of it's mounting flanges in use to properly support the load. Use only two out of the four mounting flanges and the frame could crack. If using a cheap mirror ball motor that really does not have much of a means for mounting, it should also get a similar amount of mounting bolts applied to it in mounting to a sub-frame it hangs from. Drywall screws to a block of plywood should be sufficient if only a 8" mirror ball, otherwise thru bolting would be necessary, if not steel plate dependant upon the size of mirror ball.

    A better concept is to bridge all four mounting flanges or holes so each provides equal support, and in addition to this provide a means of mounting a clamp or suspension ring in addition to safety cable.

    Could be as simple as a overly large plate sufficient in thickness that it won't bend once bolted to the flanges holding the weight. Cr create a form of marionette like I-shaped bridge of unistrut or box steel so you have clearance for a clamp to bolt to the bridge and ability to tie both bars together into a single one. Use of two Clamps where possible as spaced out as possible to prevent torque from causing a problem a single clamp might have problems with.

    Otherwise at very least if suspended, use four safety cables since they are assumed to be the same length, and link them to a ring at the center for suspension - given a forged eye-bolt can't be made to mount on the above box I-frame. What ever is used, make sure also that screws in and about the mirror ball motor are tight, and those mounting it also can't come loose from vibration.
     
  4. who_touched_the_patch

    who_touched_the_patch Member

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    Cheers and thanks much to the both of you.
    I'll post whether or not it worked on saturday.
     
  5. soundman1024

    soundman1024 Active Member

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    We used to have a mirror ball on a dimmer in my children's church. The ball worked once you got the dimmer up to about 35% as I remember right. Anyway it was up there for a few years and it was fine. There was no 'ghost bulb' on its channel just the ball. It acutally enabled us to do a few things that were slightly cooler than just having a mirror ball. For instance if it is on all the time it rotates one direction but if you turn it off and on in the right timing it will start rotating the other way. Anyway I don't know if it was just the transformer that it was using before power went to the motor, but it tended to accept the dimmer just fine. I can't tell you what brand it was.
     

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