# Dimming Motors



## brozeph20 (Oct 22, 2008)

Is it safe to put a motor on a dimmer and fade this dimmer up? Would this destroy the motor or is this possible to do safetly?


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## Les (Oct 22, 2008)

I wouldn't even put a mirror ball motor on a dimmer.


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## waynehoskins (Oct 22, 2008)

I believe I have heard that certain types of dimmers (perhaps it's the new IGBT kind?) will handle inductive loads like motors.

But no, motors don't go on dimmers. Neither the dimmer nor the motor will like it. To control a motor from the board, you generally need a relay module, which gives you on-off control only.


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## ScaredOfHeightsLD (Oct 22, 2008)

The short answer is NO. NO NO NO NO!!!!! There are a whole bunch of reasons why not to put a motor on a dimmer. The first that pops into my head is the attempt to control a motor with DMX. It's dangerous because there is no safety on a DMX system. 
It sounds like you are looking for some way to control a motor. There are many safe ways to do this depending on what you need to do. You are most likely looking at some sort of motion control system depending on the motor you are using. There are many others on here who are more qualified to talk on this so I will let them speak to it. 
Good Luck


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## soundlight (Oct 22, 2008)

NO. You'll fry the dimmer, motor, or both in short order.


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## porkchop (Oct 22, 2008)

The only possible way I see that working is if you put it on a non-dim circuit and the fact that it was plugged into a dimmer was just a convenient way to get power where you need it, but I still don't think that's a good idea. There comes a time and place were doing it the right way is the only way it should be done, motors are one of them. Perhaps if you ask a more specific question about what you're trying to do we could help you.


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## slimrocktwo (Oct 22, 2008)

What about like a Pocket Scan, or other small moving light (set to non-dim on the board)?


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## porkchop (Oct 22, 2008)

slimrocktwo said:


> What about like a Pocket Scan, or other small moving light (set to non-dim on the board)?



Once again not a good idea, but would probably work in a pinch. My fear would be that if something weird happens of the board or if you need to turn it off you're likely to cut power to the light and then you have to wait for it to rehome plus that's just not good for them.


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## brozeph20 (Oct 22, 2008)

The reason I was asking was - we are looking for gobo rotators for our upcoming show and I found a one-speed rotator. It said that you could control the speed through a dimmer (higher value, faster speed). We fortunately decided to go against this model and are going with one that has a speed contorl on the instrument.

Thank You


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## Footer (Oct 22, 2008)

A DC Motor can be controlled by varying the amount of power being sent, but it has to be DC power. An AC motor must be controlled by changing the frequency of the power going to the motor, using a variable frequency drive, or VFD. 
*
NEVER put anything on a dimmer that is not a conventional light. Ever. *


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## Les (Oct 22, 2008)

I once bought a GAM Film FX with one of those wall-wart type transformers. I was surprised when the rep told me that the way to control the speed was just to plug it into a dimmer. And it worked. The dimmer rack was an ETC Sensor 96.


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## icewolf08 (Oct 23, 2008)

dimmer that is not a conventional light. Ever.[/QUOTE]
I don't think that you can make this as a blanket statement" data-source="post: 108748"
class="bbCodeBlock bbCodeBlock--expandable bbCodeBlock--quote js-expandWatch">

Footer]NEVER put anything on a dimmer that is not a conventional light. Ever.[/QUOTE]
I don't think that you can make this as a blanket statement said:


> The reason I was asking was - we are looking for gobo rotators for our upcoming show and I found a one-speed rotator. It said that you could control the speed through a dimmer (higher value, faster speed). We fortunately decided to go against this model and are going with one that has a speed contorl on the instrument.



I know for a fact that the GAM TwinSpin II's CAN be used on a dimmer. If you doubt this you can check the manual or [autolink]call[/autolink] [autolink]GAM[/autolink]. I would also imagine that the [autolink]Apollo[/autolink] equivalent of the [autolink]TwinSpin[/autolink] is probably the same.


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## porkchop (Oct 23, 2008)

I must repent, when you said motor I was thinking something that would take a load and move truss or scenery or the like. As icewolf has pointed out there are things that have motors in them that can and in some cases must be controlled by dimming them (like gobo rotators) sorry for the confusion.


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## Van (Oct 23, 2008)

I put inductive load Mirror ball motors on my IPS dims all the time.
I use my IPS dims to control my Snow machines, Leaf droppers, flourescents, and sometimes fans. I think you can do that with a Sensor Dim as well, if you order the right kind, in advance, when you buy the system, and it's using an IBGT based dimming system, which ET invented. But I'm not biased or anything.


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## legacy (Oct 26, 2008)

hmmmmmmmmmmmmm very strange , I have been using my dimmer to control a fan for almost 5 years.,.... is this a different type motor>??


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## willbb123 (Oct 26, 2008)

legacy said:


> hmmmmmmmmmmmmm very strange , I have been using my dimmer to control a fan for almost 5 years.,.... is this a different type motor>??



For my last rock show I put a fan next to a DMX controlled hazer. I set the fan to the "2" speed and dimmed it to a speed that distributed the haze well. And it worked fine.

And I can second the post that said that you can dim GAM's Twinspin II. I doubted it at first but looked at there site and it said that you can.


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## soundlight (Oct 27, 2008)

Most of the non-dmx rotators and effects devices are dimmer-compatible. FilmFX devices, Twinspins, Vortex 360s, etc.


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## TimMiller (Oct 27, 2008)

Some mirror ball motors are designed to be dimmed, others are not. Most of the "real" mirror ball motors will not allow you to dim them due to they are capacitor start motors, and sending them anything below about 80% is not enough to get the capacitor to kick in and start the motor. When dimming things that are not made to be dimmed, you risk burning up the ssr, or whatever you are dimming. Moving lights should never be put on a dimmer search around for several threads on this topic. Also never put things such as strobe lights on dimmers to allow them to be powered up. I have seen people do this and it results in one really big pyro show from the power supply, (its not a good thing when the wrong side of the strobe flashes).


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## David Ashton (Oct 27, 2008)

More rubbish---- the fact is that "universal " motors like those used in drills and vacuum cleaners will work perfectly well on a diimmer, many motor speed controls, like the ones on drills are wave chopping circuits, just like dimmers.
What will not work on dimmers are synchronous motors, like mirror ball motors and any transformer fed motor like effects rotators.So while it is correct to say "do not put a motor on a dimmer if you don't know what you're doing" a universal motor can definitely work off a dimmer with no problem.


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## icewolf08 (Oct 27, 2008)

allthingstheatre said:


> More rubbish---- the fact is that "universal " motors like those used in drills and vacuum cleaners will work perfectly well on a diimmer, many motor speed controls, like the ones on drills are wave chopping circuits, just like dimmers.
> What will not work on dimmers are synchronous motors, like mirror ball motors and any transformer fed motor like effects rotators.So while it is correct to say "do not put a motor on a dimmer if you don't know what you're doing" a universal motor can definitely work off a dimmer with no problem.



Hate to say it, but it is a well known fact that SSR/SCR dimmers and inductive loads (ie: motors) do not play well together. Also, as has been stated, many transformer fed devices (for theatre) like rotators are designed to be able to be used on dimmers. While short term use of an inductive load on an SSR/SCR dimmer may work fine with no issues, prolonged use can lead to bad things (and it may not). So until the manufacturers tell me that it is OK to put an inductive load on a dimmer I won't be doing it.


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## derekleffew (Oct 27, 2008)

Back in the 1980s, I replaced the 3-speed switch on a cheap 20" box fan with a cheap triac-based "dining room wall" dimmer. The fan lasted at least ten summers.


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## Van (Oct 27, 2008)

TimMiller said:


> Some mirror ball motors are designed to be dimmed, others are not. Most of the "real" mirror ball motors will not allow you to dim them due to they are capacitor start motors, and sending them anything below about 80% is not enough to get the capacitor to kick in and start the motor. ..........


 
Most "Real" mirror ball motors are Shaded Pole and are usually rated 1/125th-1/5th HP. Capacitor start motors are usually reserved for something 1.5HP and above, that would be a REALLY big mirror ball.


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## TimMiller (Oct 28, 2008)

It was a 4' mirror ball. "oh ive got big balls, oh ive got big balls....." (AC/DC). So if putting a motor on a dimmer is safe than why am i paying so much for ABB inverters to speed up and down motors?


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## David Ashton (Oct 28, 2008)

if it is a synchronous motor you need a variable frequency drive, which is expensive.


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## TimMiller (Oct 28, 2008)

Yep, and they dont make 3 phase dimmers, yet i believe if you couple the control of 3 SSR's together, and then wire each of them up on the 3 legs, the SSR's will be a 3ph dimmer, but i perfer staying with the inverters or variable freq drives (VFD's). They work off of changing the voltage in to DC and then rechanging it back to AC. When you change the motor speed it actually changes the AC retification on the output side, so you are changing the frequency of the sine wave rather than the voltage, pretty cool eh?


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## David Ashton (Oct 28, 2008)

A 3 phase wave chopping motor control/dimmer cannot work because below 60 degrees of switching angle you have phase 1 on then 2 on then 3 on, so until you are over 1/3 output a motor does not see all three pases at the same time, this is the same phenomena which causes high neutral currents in dimmer systems.


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## TimMiller (Nov 7, 2008)

That is very true. Only way to truely slow down a motor is to use an inverter.


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## David Ashton (Nov 7, 2008)

You can use a 3 phase variac, or resistors, as they used to in the olden days.


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## dafunkmonster (Nov 16, 2008)

Correct me if I'm wrong, but isn't it possible to setup dimmers to either be full-on or full-off, and each state corresponds to a dmx value range?


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## Van (Nov 16, 2008)

dafunkmonster said:


> Correct me if I'm wrong, but isn't it possible to setup dimmers to either be full-on or full-off, and each state corresponds to a dmx value range?


 Yes that is what's refered to as a "non-Dim" setting. Most Consoles will allow you to set a dimmer to be at 100% at a given dmx value, eg you can set dimmer 12 to go to @full @ 10%. Meaning that anytime you set a value of 10% or more for dimmer 12 it will go to full or 100%. If You read all the previous posts you will discover there are issues with even this form of control when dealing with motors and SCRs However the original question was about the efficacy of "dimming" a motor which implies using a dimmer as a speed controller for a motor, which is a horse of a different color.


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## gafftaper (Nov 16, 2008)

dafunkmonster said:


> Correct me if I'm wrong, but isn't it possible to setup dimmers to either be full-on or full-off, and each state corresponds to a dmx value range?



"Non-dim" mode puts the dimmer in a full or off state. However the electricity is still being messed with on the way through the dimmer. The result is much different than electricity that hasn't been through a dimmer at all. Generally speaking, electronic devices do not like the results of what a dimmer does to the wave of electricity. Prolonged, and in some cases even short, use will damage an electronic device. There are some exceptions so read the manual for both the dimmer and the device. If you aren't sure call the manufacturer before plugging anything into a dimmer. 


Summary: 
-If the device has any sort of electronics in it do not plug it into a dimmer. You will probably damage it, maybe not right away, but eventually. 

-Devices without any electronic controls (such as fans and motors) may or may not work on a dimmed circuit. However, I don't think you will harm them by trying them. (Am I wrong here? Can you hurt a motor by trying it?) 

-Some devices (like the gobo rotator the original poster didn't buy) are designed to be used on dimmed circuits. 

-Always read and follow the manufacturer's instructions when it comes to selecting a power source for a theatrical device.


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## Sayen (Nov 16, 2008)

For those of us who are a little slow, what's the risk to the dimmer when running a small motor? I've seen conflicting posts around here. I have a few devices purchased before we had a workable DMX situation, and honestly wouldn't mind running them to the point of failure so they can finally be replaced, but not at the risk of my dimmers.


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## David Ashton (Nov 17, 2008)

The risk to your dimmer is practically zero.


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## TimOlson (Nov 17, 2008)

it is not safe. it will destroy the motor and possibly the dimmer. the thing that makes a dimmer fade is not the same thing that makes a motor run slower. trying to run a motor with less than the full AC waveform *I.E. dimmer* normally results in smoke.

peace, Tim O


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## David Ashton (Nov 17, 2008)

Rubbish, read the thread, a dimmer is built to survive the arcing of a theatre lamp, which is just about the most vicious act that is possible, as has been stated a dimmer will burn out a synchronous motor but any motor with brushes,[universal motor] will work fine.You need to understand that the average fan speed controller or drill controller is simply a dumbed down dimmer, but works on EXACTLY THE SAME PRINCIPLE.
It is not dangerous.


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## TimOlson (Nov 17, 2008)

allthingstheatre said:


> Rubbish, read the thread, a dimmer is built to survive the arcing of a theatre lamp, which is just about the most vicious act that is possible, as has been stated a dimmer will burn out a synchronous motor but any motor with brushes,[universal motor] will work fine.You need to understand that the average fan speed controller or drill controller is simply a dumbed down dimmer, but works on EXACTLY THE SAME PRINCIPLE.
> It is not dangerous.



I thought it would be good to ask an engineer about this before sticking my foot in my mouth. Lary Cotten wrote all the software for the LCD controllers from High End and ran the Software section of HES's R&D dept for several years. here's what Lary said:

"wow, there's are so many variations in both dimmers and motors that it's hard to give a flat answer.

An incandescent lamp is just a big resistor, and you don't connect arc / discharge lamps to dimmers, so the bit about "survive the arcing of a theatre lamp" seems a bit odd. The closest reality to that would be the inrush current into a cold filament.

If you're controlling a motor which itself has control circuitry, as in a brushless DC motor, then it's a very fair bet that it's internal controller won't care much for "dimmed" power.

For "raw" motors, i.e. no control circuitry, motors are very much inductive, which require special attention from the dimmer. This is why not all dimmers are good for low voltage halogen/tungsten lighting that uses transformers.

Dimming of nearly all types is handles using pulse width modulation, i.e. PWM, but the types of PWM range from old fashioned 120Hz zero-crossing phase control dimming, to modern "sine wave" dimmers which PWM at 50kHz plus and are filtered such that the output is basically clean AC all over again at some voltage proportional to the dim level.

Inductive loads care a whole lot about frequency of the incoming AC power, so there's a good chance the motor and dimmer won't get along.

Also, drill motors are DC motors, and nothing here specified what sort of rectification was going on between the AC dimmer and the DC motor.

I can imagine that some brushed motors would work OK with some dimmers, since those motors run at a speed proportional to average incoming voltage, but that's about it.


Keep in mind that as recently as two months ago, I've had a tech plugging in the moving lights to my dimmer packs.
They say that "it takes all kinds", but I believe that many kinds are quite optional."

so sayeth an engineer who's been creating lighting products for 20 years.

I don't think anyone would argue that not using dimmers for motors or electronics is a good idea. it's accepted standard practice, at least in the US. 

peace, Tim O


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## Benchtech (Nov 17, 2008)

I have controlled all types of motors, fans, ect from conventional dimmers, but you have to put a "ghost" load of incandescent lamps on the dimmer at the same time. Usually this load goes offstage so it isn't seen by the audience. THIS DOES NOT WORK FOR DC MOTORS AND SYNCHRONUS MOTORS LIKE CLOCKS. If you have ever taken apart a pinspot, you will find the lamp is usually a 6 or 12 volt lamp and a transformer that drops the 120 line down. This is an inductive load just like a motor. Usualy a 100 watt load works fine to fire up a box fan, which we needed to do in Peter Pan when we had to adjust the wind levels in the sails.


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## David Ashton (Nov 17, 2008)

The arcing I'm talking about is the arcing when a lamp blows and the protection which is built in to protect the output devices because 90+% of output device failure occurs due to arcing of blown lamps and the resultant extremely high current.
Universal motors are ac/dc that is why they are called universal.
The question was, can you hurt the dimmer?
The answer is still no,
I know nothing about software development, but have a lot of experience in power control, I did my training in that area.
Of course a motor with a control system built in would have problems.
I answer the questions asked.
I do not write a thesis on all the other possibilities.
Simple question-simple and correct answer.


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## bigwhiskey (Nov 24, 2008)

Dimming ac motors is tricky. We have had success progamming a effect in our lighting board. .1 second pulse every 3 second gives a nice slow turn to a ceiling fan. we have used this for years will no ill effects to dimmer or fan...


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## TimOlson (Dec 8, 2008)

LOL if you don't think an engineer involved with moving light design is a qualified source, there's no rebuttal. the thing that makes a moving light move is ..a motor! don't you suppose the software folks are intimately familiar with what makes them work, and capable of suggesting best practices?

It seem to me you're really focused on being right about this motor/dimmer thing. 

peace, Tim O


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## David Ashton (Dec 9, 2008)

Moving lights use stepper motors which are driven by electronics, these are not universal motors as used in drills, fans and power tools,you seem to be purposefully obtuse in not reading what was said instead of what you think was said.
I'll just say it once more, a universal type motor will run perfectly well off a dimmer, as a motor speed control is essentially the same as a dimmer, minus the choke and plus a capacitor, moving lights with stepper motors and synchronous motors will not work.The problem with saying that one should never run motors on dimmers is that you will look like an idiot when someone plugs a fan into a dimmer and it works fine, this destroys your credibility so that the person you gave the advice to will then try it on a synchronous motor and burn it out, this is why simplistic answers are counter-productive.
I must admit to being puzzled by the comment that drill motors are dc, all Australian and English drills run on ac.
The question was, "would I destroy the dimmer" and the answer is no, a dimmer which is protected against the huge currents which occur when a theatre lamp blows is not going to have any problem with a motor.


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## TimOlson (Dec 9, 2008)

Hi Mr Ashton, I respect what you say, and I have read the entire thread. However, given the nature of controlbooth with a large percentage of members in the beginning of their career, I would never recommend running any motor from a dimmer. Focusing on best practices early on sets good habits. Someone such as yourself, with specialized knowledge and experience, operate at a higher level of expertise and are qualified to make the judgment to go "outside the rules". I see inexperienced people running moving lights from dimmers set at full; account execs who don't want to x-rent the non-dim distro come at me with "we do this all the time and it's never been a problem". Those people don't know how close to the edge they operate, or what the long-term effects those practices create. 

So - in the mind of an inexperienced tech, if it's ok to run a fan from a dimmer, why not a chain hoist? They are both motors and if it's OK for one it's probably OK for the other, right? This type of logic occurs every day. 

If someone tries to run a drill motor or power tool or fan from the CONVENIENCE outlet on my dimmers, I'm not happy. from the dimmer itself? Absolutely Not.

There are tons of things that are done incorrectly every day, like not terminating a DMX chain & running movers from a dimmer. Problem is, these practices work for a while---until they don't. when it all comes crashing down, when strange DMX problems come up during a show, when a moving light power supply quits working during a show, the people that end up being cheated are the attendees. 

so in my mind I'm thinking about accepted best practices and learning good habits. I think there should be a clearly stated "rule" that says never run a motor from a dimmer. Once that is firmly established, then learn the exceptions. In this way we minimize confusion and maximize the professional production.

peace, Tim Olson


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