Hooking a Follow Spot into a Dimmer

In back to the follow spot question, were I doing it in modifying equipment, I would consider adding a switch to the fan. While the fan is low enough wattage to not necessitate one because it's not much of a hot patch, I still would consider a switch for the fan because using a plug for a switch in general is bad Karma. But on it's down side, it also adds to the amount of modification to the gear and back to if the spot is called out, it needs to go out concept.



The effects of a dimmer even at FF or non-dim on a ballalst in providing power to it is subject to specific details of the situation. In general it should be avoided. What about the voltage drop the dimmer even in full induces due to chokes etc, what about the effects of other dimmers or phase harmonics problems from the dimmer on the ballast? For the same reason it's not recommended that you run power tools off a dimmer, you should not run ballasts.

Given this, will it work? Probably flawlessly and often it's done I'm sure on other things such as arc source black light lamps so as to turn them off and on, or even compact fluorescents and solenoids for a kabuki drop system. Goal is not to do so rather than finding it as a primary option.
 
From my undertanding of it running a balest on a dimmer even non dim is still damageing the balest, its not ment to run on dirty power.

As i said before i dont know your fixture but think of it like this if it has a fan, balest, transformer, or moto ie (fan) its best not to run it on a dimer just dont do it find another way train your ops if its in a school mabey you just wont get the effect you want. why would you compermise the life of the gear for one look in the show?

JH
 
how exactly does it damage it though? I'm just curious I guess. it seems to me the arc lamp is the real victim. Why does the ballast care what it's getting, it's essentially a transformer. Won't the transformer just step down/up based on a solid ratio?
 
Before modifying gear for one simple effect.... try this series of calls for your look.....

Standby spots 1&2 to bump out (blackout whatever you want to call it)
And spots 1&2 to bump out on my count
and 3....
2...
1...
GO


If they can't do it at the same time with this method you have bigger problems ;)


But honestly this method has worked for me for over 12 years, even with the most questionable operators, on some of the more challenging shows, most of which I never get a rehearsal of any kind with the operators.


Oh and Bill... I've only had the opportunity to do about 30 shows at Radio City ;)
 
>>"how exactly does it damage it though? I'm just curious I guess. it seems to me the arc lamp is the real victim. Why does the ballast care what it's getting, it's essentially a transformer. Won't the transformer just step down/up based on a solid ratio?"

Even if a dimmer is parked at full, or configured as a non-dim, all of the power still goes through the SCR, and choke. Power goes into the dimmer rack as a sine wave, and comes out looking more like a square wave. Dimmers also affect the impedence of non-pure-resistive loads.

It is this square wave that will damage ballasts. Depending on the type of lamp, often ballasts also may change frequencies (some moving light ballasts output as high as 300Hz.) Additionally balllasts may do power factor correction, rectification, etc... All of these functions expect a sine wave.

Hope this helps
RB
 
sandals1621 said:
Oh and Bill... I've only had the opportunity to do about 30 shows at Radio City ;)

It is the best venue in the world in which to work... and some of the best followspot ops I've ever met.

The whole point boils down to this...

If the person calling the show uses the same words and timing for each que, i.e., Warning, Stand by, Go, and doesn't rush a call or cause confussion the results can be exactly what you want.
 

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