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LED lights on a dimmer
Old 31st January 2011
  #1
Gear Nut
 
bom619's Avatar
 

LED lights on a dimmer

I read on a web site dedicated to LED bulbs that they have varying degrees of success when used with dimmers. My current spec for a new room includes a Staco 501c running 8 Nora NLIC-601QAT sealed enclosures. The Nora unit utilizes MR-16 type bulbs and uses a transformer based power supply (solid state step down having been blamed for the dimmer problems). Does this sound practical for a studio environment?
Old 31st January 2011
  #2
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Rod Gervais's Avatar
 

Quote:
Originally Posted by bom619 View Post
I read on a web site dedicated to LED bulbs that they have varying degrees of success when used with dimmers. My current spec for a new room includes a Staco 501c running 8 Nora NLIC-601QAT sealed enclosures. The Nora unit utilizes MR-16 type bulbs and uses a transformer based power supply (solid state step down having been blamed for the dimmer problems). Does this sound practical for a studio environment?
Bomb,

I honestly have no answer for this - I am a little concerned about taking a transformer that is designed for 120 volt operation and cutting the input to it in order to try to regulate lighting levels with halogen lights.........

The right way for you to proceed would be to contact the engineering dept at Nora and ask the question of them.

The LED lights have no dimming issues as long as they are specifically design for dimming - you should never use a fixture designed for constant lighting and try to dim it.

You also have to use a dimming system specifically designed for LED fixtures......
Old 1st February 2011
  #3
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jhbrandt's Avatar
Quote:
Originally Posted by Rod Gervais View Post
....The right way for you to proceed would be to contact the engineering dept at Nora and ask the question of them.

The LED lights have no dimming issues as long as they are specifically design for dimming - you should never use a fixture designed for constant lighting and try to dim it.

You also have to use a dimming system specifically designed for LED fixtures......
++1!

- John
Old 1st February 2011
  #4
cork sniffer
 
Ron Vogel's Avatar
 

LED dimmers don't actually "dim" the bulb. It uses a PWM (pulse-width modulation) to dim it. It's like turning on and off a switch REALLY fast, while holding it in the on postion for varying amounts of time to control it's brightness.

I've built several PWM switches for automotive purposes (like controlling a fuel injector). It's not a complicated circuit, but that's how it's done.
Old 1st February 2011
  #5
Gear Nut
 
bom619's Avatar
 

LED dimmers

What off the shelf systems are available and suitable for studio use? I am hoping to use 6" overhead lighting.
Old 1st February 2011
  #6
Lives for gear
Ron Vogel is correct about PWM - that is the best way to dim LEDs

You can dim via a pot etc like a normal dimmer but can be less successful as there is a threshold of voltage for the LED to turn on and then a small amount of increased brightness to be obtained and is really easy to blow. Basically there is not much headroom once the LEDs have enough power to come on

So you go from medium high brightness to maximum, but with a proper LED dimmer you can go from off to low to high due to PWM, LEDs love being turned on and off REALLY quickly, conventional lights don't. Also LEDs use even less power through PWM then constant electricity via a conventional dimmer for the same brightness.
Old 4th February 2011
  #7
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once a roadie's Avatar
PWM controllers will spew noise all over the place. Watch out.
Old 4th February 2011
  #8
Quote:
Originally Posted by bensaddiction View Post
Ron Vogel is correct about PWM - that is the best way to dim LEDs

You can dim via a pot etc like a normal dimmer but can be less successful as there is a threshold of voltage for the LED to turn on and then a small amount of increased brightness to be obtained and is really easy to blow. Basically there is not much headroom once the LEDs have enough power to come on

So you go from medium high brightness to maximum, but with a proper LED dimmer you can go from off to low to high due to PWM, LEDs love being turned on and off REALLY quickly, conventional lights don't. Also LEDs use even less power through PWM then constant electricity via a conventional dimmer for the same brightness.


It's a bit more complicated than that.

Your typical light dimmers for incandecent AC bulbs use a form of dimming that is much like PWM. It's generally called "phase control dimming". Basically, each time the AC waveform goes through zero, the AC is cut off from the bulb and doesn't come back on for a portion of the half-cycle (real geeks refer to the percentage in degrees of phase).

To make things more complicated, National Semiconductor has a PWM that controls the average current applied to a string of LEDs. What makes the new chip impressive is that it rectifies the AC so that it has a reserve of power and samples the phase delay of a standard dimmer. So, you can make a LED light that responds properly to a standard dimmer...

I actually saw a product based on this in the hardware warehouse store the other day.



-tINY

Old 4th February 2011
  #9
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Quote:
Originally Posted by tINY View Post
To make things more complicated, National Semiconductor has a PWM that controls the average current applied to a string of LEDs. What makes the new chip impressive is that it rectifies the AC so that it has a reserve of power and samples the phase delay of a standard dimmer. So, you can make a LED light that responds properly to a standard dimmer...
Great stuff. You would not happen to know the part number would you?

Andre

Last edited by avare; 4th February 2011 at 04:29 PM.. Reason: Corrected HTML
Old 4th February 2011
  #10
LM3445 - Triac Dimmable Offline LED Driver


LM3445. I was gonna order the design example board to play with, but my baby boy and the move across town have taken their toll on my schedule lately.




-tINY

Old 4th February 2011
  #11
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avare's Avatar
 

Quote:
Originally Posted by tINY View Post
LM3445 - Triac Dimmable Offline LED Driver
[FONT="comic sans ms"][COLOR="indigo"]
Thank you.

Andre
Old 4th February 2011
  #12
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gullfo's Avatar
 

there are plenty of LED replacement lamps which can be used with regular dimmer circuits or use LED specific dimmers for a broader range of LED lights. or better yet, use several circuits and connect up various numbers of LED per circuit to vary the lighting and reduce the risk of having the dimmer or bulb causing noise (acoustically or electrically).

here's just one site (selected from a Google search) which has dimmable LED replacement lights. EarthLED LumiSelect Dimmable LED Light Bulbs, Dimmable LED, LED Lamps, Dimming LEDs, Dimmer Compatable LED Lamps
Old 5th February 2011
  #13
Gear Nut
 
bom619's Avatar
 

Mr16 led

Thanks Gullfo. All the big box stores in my city have MR16 LED bulbs that are supposedly compatible with consumer dimming systems but I haven't seen a word about them in the usual studio build forums. From what I have read, the enclosures with solid state step downs (MR16's are 12V) will cut off completely below a certain threshold while the transformer based units will give you a full range (similar to what we have all enjoyed with the Luxrol/incandescents). Was hoping to confirm this with some fellow gearslutz prior to my build. I may have to build a jig and try it myself.
Old 12th April 2011
  #14
All the big box stores in my city have MR16 LED bulbs that are supposedly compatible with consumer dimming systems but I haven't seen a word about them in the usual studio build forums.

This was my question as well. I bought a few to try in out in a build/studio remodel I am working on now. The dimming works fine with standard dimmer switches, but i want to know if they cause EMI/RFI noise. Does anyone know if the dimmable LED light bulbs are QUIET?
Old 12th April 2011
  #15
Gear Nut
 
bom619's Avatar
 

LED + dimmers

So far, not a word of first hand experience. I have two projects coming up this year that will give me an opportunity to try these things so I will keep everyone posted.
Old 12th April 2011
  #16
vfr
Gear Maniac
 
vfr's Avatar
 

I've used dimmers on the red LED rope lights that I use in my telescope's observatory and they work fine. I have heard about the noise issue though and haven't used them under other settings. They worked fine for my purposes.
Old 12th April 2011
  #17
Quote:
Originally Posted by panhandler View Post
All the big box stores in my city have MR16 LED bulbs that are supposedly compatible with consumer dimming systems but I haven't seen a word about them in the usual studio build forums.

This was my question as well. I bought a few to try in out in a build/studio remodel I am working on now. The dimming works fine with standard dimmer switches, but i want to know if they cause EMI/RFI noise. Does anyone know if the dimmable LED light bulbs are QUIET?


Depending on the design and build quality of the light itself, you could have EM noise issues. Generally, the hum/buzz from the AC line transients should be greatly reduced to the point that they are not an issue.

If you have the bulbs, get a single coil guitar and a high gain amp and see if it's an issue...



-tINY

Old 19th April 2011
  #18
Thanks Tiny. Makes sense. I will get a guitar and give it a whirl.
Old 3 weeks ago
  #19
Gear Addict
 

Renovating my studio and I am wondering about LED lights and suitable quiet dimmers.
Old 3 weeks ago
  #20
I have been using a STACO dimmer (autoformer) and these bulbs *https://www.amazon.com/gp/product/B0...=UTF8&psc=1)in my HALO track system with no problems. FWIW
Old 3 weeks ago
  #21
Gear Addict
 

Quote:
Originally Posted by Thomas W. Bethe View Post
I have been using a STACO dimmer (autoformer) and these bulbs *https://www.amazon.com/gp/product/B0...=UTF8&psc=1)in my HALO track system with no problems. FWIW
Do you have a link to the dimmer you use?
Old 3 weeks ago
  #22
It is similar to this one https://www.amazon.com/New-Technipow...ag=googhydr-20 and I purchased it used from HGR Sucuri WebSite Firewall - Access Denied The unit says STACO on the autoformer/variac dimmer.
Old 3 weeks ago
  #23
Gear Addict
 

Quote:
Originally Posted by Thomas W. Bethe View Post
It is similar to this one https://www.amazon.com/New-Technipow...ag=googhydr-20 and I purchased it used from HGR Sucuri WebSite Firewall - Access Denied The unit says STACO on the autoformer/variac dimmer.
Thanks, but I need a standard size dimmer that will fit in standard electrical boxes.
Old 3 weeks ago
  #24
Quote:
Originally Posted by Victory Pete View Post
Thanks, but I need a standard size dimmer that will fit in standard electrical boxes.
Then check out this Satco Products, Inc |

Where can I find a dimmer that is compat...


Best of luck!
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