Is it safe to run moving lights off of a dimmer?

[Swade White]

Hello ControlBooth,

I'm no electrician so I figured I would ask some people that know what they are doing before I just do it. I am wondering if it is safe to run moving lights and some LEDs off of a dimmer rack (ETC Sensor3). Our current situation requires us to run extension cords up to the electric battens and plug them into Edison outlets on the stage floor. This is very inconvenient when we need to lower or raise the electrics and also because it is using up most of the outlets on stage level. I am wondering if I were to replace the Edison plugs on all the automated lights with stage pin ones, would that be safe for both the electrics inside the light and even the dimmers themselves? We have an ETC Element so I would just set a non-dim and grand master exempt for those specific channels that they are plugged into. We have 4 Vari-lite VL2500's, 6 random generic 36x10w LED Moving Heads that I found on eBay, and 4 Elation EPAR QA LED par cans. Thanks!

Edit: Writing this got me thinking... Would this method also work on something like a cheap LED strip that you put behind the cyc so actors can see where they are going? If so, it would be cool to incorporate LED strips into the scenery of our next musical.

 

[MRW Lights]

Without a little more information the first answer you're likely to get is no. It's not necessarily safer to you either way. There's probably more of an argument to say the stage pin is more dangerous for both you and the light. Motors and LEDs are usually fans of constant and consistent power. Your sensor rack can be equipped with different modules to accomplish what you're looking to do, but generally speaking you're going to want to avoid putting LED's or Motors on a dimmer.

 

[TNasty]

As I was told in one of my previous threads, no. You'd be best off having a relay "dimmer" (simply toggles a 120v line).

The reason being that the dimmer may still be in a mode where it'll allow dimming.

About your edit: I'm pretty sure a RGB DMX decoder is what you're looking for. Same deal with the variable power, though. Just use the decoder to control a nice, cheap strip of RGB led's you can buy on amazon (or eBay).

 

[Swade White]

As I was told in one of my previous threads, no. You'd be best off having a relay "dimmer" (simply toggles a 120v line).

Your sensor rack can be equipped with different modules to accomplish what you're looking to do, but generally speaking you're going to want to avoid putting LED's or Motors on a dimmer.

Do you know what the module is called? I would defiantly purchase some of those to get this done.

 

[TNasty]

Do you know what the module is called? I would defiantly purchase some of those to get this done.

It's the ETC R20 Dimmer Relay Module.

 

[Swade White]

It's the ETC R20 Dimmer Relay Module.

Alright thanks for your help!

 

[JohnD]

With the Sensor 3 you have several module options.
The R20 relay module and the CC20 constant current module.
They are both two circuit modules, so if you replace a dimmer module you will have two non-dim circuits wherever the dimmer module was wired to.
Then there is the ThruPower module which is a switchable dim/non-dim per circuit module, so if you only need one non-dim circuit you could use that. It is more expensive however.
EDIT: You should be able to rent the module(s) if your current budget won't allow you to purchase them now, lets you see how they work in your space.
Also, instead of changing the edisons to stage pins, I think you should just build some short stage pin to edison adapters, they always come in handy.

 

[ChrisB_SanDiego]

First off I am NOT a qualified electrician

I have been doing what you are speaking of for a while with 12 Clay Paky HPE 300's and 5 cheap led strips, all of the LED's are plugged into dimmer modules on an ETC dimmer rack as well as half the movers... these are using actual dimmer modules. the other half of movers are relay modules that can be put in the rack instead. In theory, the relays are safest for your movers but I haven't had any issues with running it on a dimmer circuit.
With an ION In patch I have these set as generic non-dims at full. I just park the channels as soon as they come on... in theory, that means that it's either off or on, but in reality, there is a slight dim curve at initial turn on and then a constant full. With my setup I don't witness any dimming happening when set at full. Note: with the original install all the movers were put on relays however since then I have moved some stuff around...

I have been using this setup for around 5 years with no issues with the lights and no noticeable difference between movers on relays and the ones on dimmers. Also on portable gigs I'll do the same thing with NSI 4 channel dimmers, but on those, you can dip switch the settings to be constant on off.

I would strongly suggest new stagepin connectors that are nice and snug to plug in so you have good contacts and put a meter on it before plugging your lights in to see if the voltage stays constant.

Is it the proper way? Probably not, but I have seen plenty of touring gigs come to our venue doing the same thing (although a lot of them are custom made socopex snakes to the movers, but still on dimmers)... as long as the lights are getting proper voltage than they're happy, although I'm sure some will tell you its unnecessary wear on the lights.

Neither are necessarily safer, although stagepin, especially old stagepin could be more dangerous since it could get knocked out completely or have exposed contacts quite easy if tripped on, or you could say stage pin in safer since you don't have to actually work with the modules, not to mention they are a lot cheaper than the relays ;-)

just make sure the whole rack is off when working on it... ALWAYS handle electricity with care and no distractions.

 

[RonHebbard]

With the Sensor 3 you have several module options.
The R20 relay module and the CC20 constant current module.
They are both two circuit modules, so if you replace a dimmer module you will have two non-dim circuits wherever the dimmer module was wired to.
Then there is the ThruPower module which is a switchable dim/non-dim per circuit module, so if you only need one non-dim circuit you could use that. It is more expensive however.
EDIT: You should be able to rent the module(s) if your current budget won't allow you to purchase them now, lets you see how they work in your space.
Also, instead of changing the edisons to stage pins, I think you should just build some short stage pin to edison adapters, they always come in handy.

This thread's feeling like Deja vu all over again.
Toodleoo!
Ron Hebbard

 

[Wheezy]

The short answer is no. A dimmer module uses a different method to get from 0 to 120volts than a relay module. Intelligent lighting power supplies could fail prematurely without stable voltage. Also, if power is removed to a DMX controlled LED, the fixture could restore to default when you least could afford it.

Disclaimer: I, like others, run off of dimmers all the time. Real life being what it is.

Now to the bigger issue. RonHebbard, aren't extension cords in the battens against code?

 

[JD]

Short answer, NO. You can do it, but unless your "Relay" module goes "Click" (contains an actual mechanical relay), then you are taking a chance twofold.
1) If you somehow end up out of relay mode and dim it, the switch-mode power supply in the mover will go crazy.
2) An SSR (or would that be "a"?) has to develop voltage across it before the firing circuit can fire, so even at full, there is a chop in the waveform that some electronics won't like.

 

[RonHebbard]

The short answer is no. A dimmer module uses a different method to get from 0 to 120volts than a relay module. Intelligent lighting power supplies could fail prematurely without stable voltage. Also, if power is removed to a DMX controlled LED, the fixture could restore to default when you least could afford it.

Disclaimer: I, like others, run off of dimmers all the time. Real life being what it is.

Now to the bigger issue. RonHebbard, aren't extension cords in the battens against code?

I wouldn't think so as long as they're at least 12/3 S or butcher. I suspect legally they can be colors other than black but several of us here will cause you to suffer a slow, painful, death if your cables are any color than black.
Paging @STEVETERRY
Toodleoo!
Ron Hebbard

 

[STEVETERRY]

"aren't extension cords in the battens against code?"

I'm not sure what the poster means by "in the battens".

Extension cords are allowed in a theatre covered by NEC article 520 as long as:

1. They are an extra-hard usage type (type S and derivatives).
2. They are used to feed a load not greater than specified by the listing of the extension cord, if it is listed as an assembly
3. They are used to feed a load not greater than that specified in NEC table 400.5(A)(1) if they are "field assembled" from listed cable and connectors.
4. They are protected by an overcurrent device not greater than the extension cord listing allows, if it's listed as an assembly.
5. They are protected by an overcurrent device per NEC 240.5 if they are "field assembled". This resolves to 16AWG minimum on a 20A circuit.

ST

 

[JChenault]

"aren't extension cords in the battens against code?"

I'm not sure what the poster means by "in the battens".

Extension cords are allowed in a theatre covered by NEC article 520 as long as:

1. They are an extra-hard usage type (type S and derivatives).
2. They are used to feed a load not greater than specified by the listing of the extension cord, if it is listed as an assembly
3. They are used to feed a load not greater than that specified in NEC table 400.5(A)(1) if they are "field assembled" from listed cable and connectors.
4. They are protected by an overcurrent device not greater than the extension cord listing allows, if it's listed as an assembly.
5. They are protected by an overcurrent device per NEC 240.5 if they are "field assembled". This resolves to 16AWG minimum on a 20A circuit.

ST

Steve. Did the wire gauge for 20 amp circuits change recently. I thought 12 gauge was required for a 20 amp load? Was I always wrong or has the truth changed?

 

[STEVETERRY]

Steve. Did the wire gauge for 20 amp circuits change recently. I thought 12 gauge was required for a 20 amp load? Was I always wrong or has the truth changed?

John--

These are two separate issues that are commonly misinterpreted:

1. The ampacity of a portable cord is determined by the listing of the extension cord (if it is listed as an assembly), or by NEC table 400.5(A)1) if it is not listed as an assembly. In the latter case, 12AWG is rated for 20A.

2. The required overcurrent protective device rating to safely protect a portable cord is determined by NEC section 240.5, and is not the same as the ampacity of the cord. Thus, a cable as small as 16AWG may be connected to a branch circuit with a 20A overcurrent protective device.

3. A portable extension cord may never supply a load greater than its ampacity rating as determined by (1) above.

ST

 

[gafftaper]

As I was told in one of my previous threads, no. You'd be best off having a relay "dimmer" (simply toggles a 120v line).
The reason being that the dimmer may still be in a mode where it'll allow dimming.

Close but not quite. When you put a dimmer into a non-dim mode, the electricity get's messed with and then reassembled at 100% power on the way out of the dimmer. It's now all on or all off. All the steps between 0 and 100% are disabled. This is not the same as never having been through a dimmer in the first place. If you pull a constant module form the rack you see no guts at all. Just a circuit breaker on the front and a cable to the back. If you pull a relay module, you see a circuit breaker, a couple wires and a dmx controlled switch in the line, but it's still quite empty. The power isn't altered at all, it's just switched on and off remotely. When you pull a dimmer module you see all kinds of parts that make up the dimming process. When you put the dimmer in non-dim mode, there's no way for the electricity to bypass this process and run at 100%. In "non-dim mode" it still get's chopped up and reassembled, it just goes from 0 to 100% with no stops in between. It's this unavoidable process of what the dimmer does to the electrical wave form which can potentially damage your electronic gear.

Finally, as has been noted in the real world many products run fine for a long time off of dimmed power with now damage. But you also might plug in a $10,000 mover and kill it the first time you power up. I'm not willing to take that risk. Are you?

 

[JD]

John--

These are two separate issues that are commonly misinterpreted:

1. The ampacity of a portable cord is determined by the listing of the extension cord (if it is listed as an assembly), or by NEC table 400.5(A)1) if it is not listed as an assembly. In the latter case, 12AWG is rated for 20A.

2. The required overcurrent protective device rating to safely protect a portable cord is determined by NEC section 240.5, and is not the same as the ampacity of the cord. Thus, a cable as small as 16AWG may be connected to a branch circuit with a 20A overcurrent protective device.

3. A portable extension cord may never supply a load greater than its ampacity rating as determined by (1) above.

ST

I have seen this issue and discussion pop up several times over the years. The last time had to do with a cable feeding a 100 watt ghost light. Indeed, the key factor is the load, and that the cable is "extra hard duty" (Type S, ST, SO)
That said, there are often in-house rules about using 12/3 minimum. The justification is that things sometimes get added on the fly and you don't want to end up using a cable with a rating below what you have loaded on it.

 

[EdSavoie]

It all comes down to how the PSU is designed. a robust design could use any number of methods to be adequately powered off a dimmer. It's simply a matter of (slightly) more expensive production costs.

 

[Aaron Clarke]

I tried it once saying I'm extra careful, what can it hurt. 3 hours before show I go to move the board to the booth and someone distracts me. As I stand there talking to them the preprogramed DMX failure mode kicked in (I might have not checked that) which happened to be a 15 second fade. As soon as I saw the house lights start going a lot of words not appropriate for the venue (school) came out of my mouth. Hooked up and powered up to find the fuse on every fixture toast. It's an 1hr 15min one way to the closest place that has enough fuses. Lets say I made it in 1hr and was powered up 15 minutes before curtain. NEVER AGAIN but thankfully the fixtures were good once the fuse was replaced. NEVER AGAIN. The though has crossed my mind but then I remember that night.

 

[RonHebbard]

I tried it once saying I'm extra careful, what can it hurt. 3 hours before show I go to move the board to the booth and someone distracts me. As I stand there talking to them the preprogramed DMX failure mode kicked in (I might have not checked that) which happened to be a 15 second fade. As soon as I saw the house lights start going a lot of words not appropriate for the venue (school) came out of my mouth. Hooked up and powered up to find the fuse on every fixture toast. It's an 1 hr 15 min one way to the closest place that has enough fuses. Lets say I made it in 1 hr and was powered up 15 minutes before curtain. NEVER AGAIN but thankfully the fixtures were good once the fuse was replaced. NEVER AGAIN. The thought has crossed my mind but then I remember that night.

Congratulations on learning a valuable lesson. Fye on those who claim our schools are failing us. There you were in school and, even while chatting, you learned a valuable lesson. Seriously; Congrats! Now all you've got to do is remember it (and pass it on to others)
Toodleoo!
Ron Hebbard.