Glass Grenade? at DVinfo.net

John Ekis · January 2nd, 2007, 07:21 PM

Please help! So I hooked up a dimmer switch that I bought from B&H to one of my Impact 500 watt lights. I noticed immediately that there was some kind of white smoke swirling around filling the bulb. I shut it off in fear that it could explode in my face. I tried it once again and sure enough the same thing happened. I'm afraid to try another bulb right away because I don't know if what I'm doing is not good for the bulb or what the deal is. The dimmer is rated for 600 watts so I didn't think that would be an issue. Although, the dimmer is designed for a non-grounded plug so I have an adapter from a 3 prong to 2 prong going into the dimmer. I made some DIY dimmers that work except the lights give off a buzz when I dim them. Does anyone know was is going on? Any knowledge of this would be extremely appreciated.. thanks!

Steve Leverich · January 2nd, 2007, 07:57 PM

See if this helps -

http://www.sprags.com/

Didn't read the whole thing, but the link to buzzing problems should answer a lot. Basically, the further you dim a light with an SCR or Triac type dimmer, the "spikier" the waveform becomes - this is due to the really fast switching time these devices are capable of. Higher quality dimmers attempt to lessen this effect with filtering, which helps some. But most incandescent/halogen filaments will physically MOVE when pulsed this way, and this is where the actually audible humming comes from. This also stresses the filament, shortening its life.

The smoking part seems kinda weird though - did you try these lights with full power right from the outlet to see if they still do this? I'm thinking it might just be "baking out the new-ness", or something.

Another 'way-out possibility - maybe your specific filaments have a physical resonance that coincides with line frequency, and they're gonna vibrate with ANY 60 hZ source??!? Dunno, just some "random neuron firings"... Steve

Bill Hamell · January 3rd, 2007, 06:24 PM

First these types of lights are not meant to be dimmed.

The first thing to do is plug the light in by itself does it still smoke?
If it does than it’s not the dimmer and probably just some kind of oil on the light or bulb.
Is it a new light? If it is it’s probably something left on it from manufacture and will burn off in a few minutes. If you handled the bulb with bare hands its oil from your hand burning off and you are correct it could explode so carefully wipe it off (after it has cooled) using a clean cloth and some alcohol and it should be fine.

When you dim these lights the color temperature changes and this can cause color shifts. (this why you should not dim these lights.)
To control the amount of light you use distance (from your subject) and or scrims and flags.

Bill

Bob Grant · January 7th, 2007, 03:14 AM

By any chance is the Impact 500 one of those lights designed for use in photo studios?
If so I suspect it has a fan in it.
That's probably what's making the buzzing sound, the fan motor.
It'll also explain the smoke, the lamp isn't getting enough airflow.

In other words do NOT try to dim this light, unless you can separate the feed to the lamp from the feed to the fan so when you dim the lamp you don't slow down the fan.

January 2nd, 2007, 07:21 PM	#1
John Ekis New Boot Join Date: Jun 2005 Location: Naperville, IL Posts: 13	Glass Grenade? Please help! So I hooked up a dimmer switch that I bought from B&H to one of my Impact 500 watt lights. I noticed immediately that there was some kind of white smoke swirling around filling the bulb. I shut it off in fear that it could explode in my face. I tried it once again and sure enough the same thing happened. I'm afraid to try another bulb right away because I don't know if what I'm doing is not good for the bulb or what the deal is. The dimmer is rated for 600 watts so I didn't think that would be an issue. Although, the dimmer is designed for a non-grounded plug so I have an adapter from a 3 prong to 2 prong going into the dimmer. I made some DIY dimmers that work except the lights give off a buzz when I dim them. Does anyone know was is going on? Any knowledge of this would be extremely appreciated.. thanks!

January 3rd, 2007, 06:24 PM	#3
Bill Hamell Major Player Join Date: Aug 2004 Location: Mystic Ct. Posts: 477	First these types of lights are not meant to be dimmed. The first thing to do is plug the light in by itself does it still smoke? If it does than it’s not the dimmer and probably just some kind of oil on the light or bulb. Is it a new light? If it is it’s probably something left on it from manufacture and will burn off in a few minutes. If you handled the bulb with bare hands its oil from your hand burning off and you are correct it could explode so carefully wipe it off (after it has cooled) using a clean cloth and some alcohol and it should be fine. When you dim these lights the color temperature changes and this can cause color shifts. (this why you should not dim these lights.) To control the amount of light you use distance (from your subject) and or scrims and flags. Bill __________________ Cinematographers Bring Shadow To Light

January 2nd, 2007, 07:57 PM	#2
Steve Leverich Regular Crew Join Date: Sep 2006 Location: Albany Oregon Posts: 173	See if this helps - http://www.sprags.com/ Didn't read the whole thing, but the link to buzzing problems should answer a lot. Basically, the further you dim a light with an SCR or Triac type dimmer, the "spikier" the waveform becomes - this is due to the really fast switching time these devices are capable of. Higher quality dimmers attempt to lessen this effect with filtering, which helps some. But most incandescent/halogen filaments will physically MOVE when pulsed this way, and this is where the actually audible humming comes from. This also stresses the filament, shortening its life. The smoking part seems kinda weird though - did you try these lights with full power right from the outlet to see if they still do this? I'm thinking it might just be "baking out the new-ness", or something. Another 'way-out possibility - maybe your specific filaments have a physical resonance that coincides with line frequency, and they're gonna vibrate with ANY 60 hZ source??!? Dunno, just some "random neuron firings"... Steve

January 7th, 2007, 03:14 AM	#4
Bob Grant Trustee Join Date: Nov 2005 Location: Sydney Australia Posts: 1,570	By any chance is the Impact 500 one of those lights designed for use in photo studios? If so I suspect it has a fan in it. That's probably what's making the buzzing sound, the fan motor. It'll also explain the smoke, the lamp isn't getting enough airflow. In other words do NOT try to dim this light, unless you can separate the feed to the lamp from the feed to the fan so when you dim the lamp you don't slow down the fan.