Hooking a Follow Spot into a Dimmer


I am looking for a way to get the cut off times of 2 followspots to be the same. The idea proposed by someone on my lighting crew was run it through our backup Leprechon system. This would be just used for 100% and 0%, nothing inbetween. Can a spot be used like this or will it cause problems for it? The spots would be left on all the time and power controlled by the dimmer. We have 2 Altman Comets that draw 360 watts. Electrically we are running the dimmer out of a 20A 120V outlet, giving 2400W, so overloading is not an issue.

I dont know your fixtrues,but if they have a balest or a transformer built in to them then do not hook them up to a dimmer you will kill the fixture. most folow spots have a transformer or a balest so i wouldnt risk it. just have the operators practice till they get it right thats how the rest of the world does it.

if it has a balest or not you can go ahead and plug it into the dimmer. Just make sure the channel is set on nondim or whatever which will basically turn it into a switch, so 0%=0% and 1-100%=100%, kapeesh? Otherwise it's fine.
Thats not true you will still damage the balest because it is not 60 cycle a second power that has even peaks it will mess with the inner workings of the balest and anyway he wants to dim out two spots at once.

do not no matter weither you set it to non dim or not plug a follow spot into a dimmer. the same goes for moving lights.

i reapeat do not plug it in, if it has a balest or transformer you will damage the fixture.

In my earlier day I played around alot with flourescent lights and dimmers, the two do not play nicely together for long!!!!
Remember also that followspots require some time to "warm up". If you just turn them on from the dimmer, you'll have very poor light from the followspot until the bulb warms up and becomes brighter.

I would recommend just using the dowser on the followspot. It takes some training, but doing it that way is better than having something look like crap.

Just my 2¢.
First off, he said he doesn't need to dim them, he's only using the dimmer as a means of switching them off at the same time. That should work alright with the ballast, as at 100%, the lights are getting a full 60hz signal.

Why not just call the cue and have the ops practice enough to turn them off together?

I guess I get what you're saying about the ballast if it were dimming. However, he could always use a sine-wave dimmer and that should work. :)

Also, I'm pretty sure his fixture doesn't use a ballast, which makes the whole thing pretty moot.
The FLE comet lamp is a halogen MR-16 lamp which is 360w/82v. Dimming/setting them to go or not go in power won't be a problem.

Only problem should be in if there is a cooling fan, dimming them could cause problems to that fan, and killing the power to the lamp cold kill the power to the fan which even if halogen could have dire effects on the lamp cool down rate.

Be cautious of that cooling fan, otherwise the lamp if seperate should work perfectly fine if not even dimmed by a dimmer.

Beyond this however, practicing and timing of cues should solve the problem in a much more simple way.
When I have this problem, I hook both of our followspots up to a power strip, and then just turn the switch on the power strip on and off. No issue of dimming. But, ship is right, there would be a problem if they had been running for a significant period of time and the cooling fan was turned off as well as the bulb. The bulb would stay hot for much longer. I didn't have this problem because when I did this, it was only for a minute or two each time that they were turned on.
Dimming a spot

OK here’s my two cents…

I think the Altman Comets are similar to my Dyna spots in lacking a ballast. I use my two with the dimming system all the time. (my throw distance is only 40ft) Even though you don’t need to dim them you should rewire them with a double pole single throw switch. Then run a separate power feed for just the fan on one pole of the switch and run the lamp through the other. Remember to not use the ground on the fan, just the one on the lamp, (which gets plugged into the dimmer). This way you don’t take a chance on a ground loop. Now you can always dim the lamp and the fan will still run on full 120v and all the operator does is throw one switch. When I callstandby spot” my operators turn on the switch and then I call “go spot” and hit the cue button, lamps come on and all is right with the world. Then after the cue for "spot out", they can leave the fan on for a few minutes. Trust me, its nice to be able to dim out the spots at times. (I’ve always hated the effect of just shutting them off) Most dimmers produce some sort of “dirty voltage, even at 100%, and that will kill the fan eventually. (and those ballasts too) (I know, its minimal and you need an good oscilloscope to see it)

Of course, you could just practice to get the timing down…but I like to make things complicated…
The Altman Comet followspots do have a transformer which will not be happy if dimmed.

The method in which an LD "calls" the cues has a great deal to do with how accurate the operators of the spots perform.

It is standard practice in theatre to call a cue as follows:

1 - Warning on cue #___, followspots to blackout.

2 - Standby on cue #___.

3 - And GO.

If the LD issues the warning at 30 seconds before the cue and the standby at 10 seconds, both operators will be ready for the GO command.

The word AND can be elongated if necessary to reach the exact moment required and the operators should practice executing the command on the G part of GO.
ok... i have no clue what you are all talking about with ballests in followspots.... i guess i'm used to short and medium throw spots that use tonguston-halogen lamp...

as far as the cooling fan.... such as on the altman followspot...

if you feel confortable, crack open the light and wire the cooling fan to a seperate lead... you'll end up having to drill a hole in the metal housing to run the cable through... but then the fan is on a seperate lead that can be given constant power and the lamp will run off of the orriginal lead and can be on the dimmer...
I'm surprised nobody has mentioned that even though you kill the power, they will still be some degree of afterglow from the filament cooling down.

With some good cue calling, and practice of the ops it shouldn't be an issue to mechanically have them both douse out at the same time.
But what do I know 7 national tours as lead frontlight. :)
Actually he did add something. He reafirmed my post.

And as an touring LD for over 15 years and having called more than 40 shows at Radio City Music Hall, I can tell you he's right.

I'm too old to be modest . . . LOL
There is a reason fixtures like follow spots have fans

1 depending on the type of bulb it can explode if it cools to rapidly

2 the materials used in the construction of the fixture cant handle that much heat.

either way if it has a fan it doesnt like to be shut off with out letting the bulb cool off. so forget that nasty affter glow you could still have a componet damaged in the system or have an expensive and potentialy dangerous bulb explode.

A Ballasts:
"Ballasts are electrical devices that convert line current into the proper voltage, amperage, and waveform" quoted from


now that site is talking about fluorescent lamps but they are used on carbon arc lamps and bigger follow spots use carbon arc lamps.
rrrrright, but look at his followspot. It doesn't use carbon arc lamps.

I agree about dimming ballasts, there's no disputing it, I'm just saying he isn't dimming his power, so would there be a problem in using a nondim circuit to power a ballat.
Same thing with the fan. We all seem to be saying the same thing, calling the cue would be best.
Seperating the power feeds is ok in general but the point is that those follow spot operators will do their job in following their cues or be replaced. Wiring up the fan for a secondary power feeding of it can at times mean it's left on all night long. This in addition to while for the most part simple to do - given you take into account heat within the fixture. (Will a 60c, 75c or 90c cord melt down in an unsafe way?)

It also in modifying the fixture negates it's UL listing which even if well done might not be permissible by way of the governing authority.

Not so sure about creating a grounding loop or given it's a filament lamp what sort of problems this would cause for it. What I am sure of however is it's probably not wise to have the fan power source lack it's ground. What if a wire comes loose? If the lamp is off, and perhaps dimmer is un-plugged, you now have a fixture with potential but no escape for that potential. Same story with a ground to the fan/fixture but not lamp. What if a lamp wire comes loose in touching the frame, but the fan power is not plugged in?
Man I had a big long post about how poeple are in school to learn and the diffrences between the real world and school but it got deleted when I tried to post it. I will give you the short version.

High school and college are places where the main goal should be education. With enough practice you will produce two very well trained spot ops. That should be the goal of high school and college theater. Leaving having perfect shows and filling house to the pros.

Not to say running sloppy shows is ok, everyone should be striving to be the best, but if the Ops do not learn how to take a cue now when will they?
Ok, I took too long to post the last one and missed out on the last 3 or so comments after ship's. But I want to add on a bit to soundman's comment and say that spot op is certainly an underrated job. A good spot op is worth their weight in.....mac 500s.

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