Skip to main content

Reply to "black lights"

Continuing on now:

The buzzing noise is known as lamp sing, it's caused by the power being turned on and off really fast. The way this is fixed is more expensive dimmers have what is known as a choke after the SCR so the power change is as dramatic as on/off. The better the quality of dimmer, the less lamp sing you will get.

Now why non-dim isn't really non-dim. Despite you setting a dimmer to non dim, either via the pack or the console, the power still passes through the SCR and choke. So, the power is still being turned on and off extremely fast. Now there are more modern dimmers that by-pass the SCR and choke when switched to non-dim on the dimmer itself, making it a true non-dim dimmer.

I believe Elation's DP-640B dimmer pack is an example of this, but without a wiring diagram to look at, I can't be sure. Maybe jingles or Elation_Pro can comment on this and answer this for us.

Now why are things like fluorescents bad for the light and/or dimmer. First, in-rush currents. An in rush current is caused by a lower resistance in the circuit. This is caused by cold filaments in tungsten lamps. A filament's resistance can be as much as 1/17th of what it is when it is hot. Remember, heat is the enemy, more heat, more current, more chance for things to break. Let's look at Ohm's Law and the Power real quick to understand this. Warning, this next section contains use of algebra Wink.

Ohm's law states that V=I*R where V=Voltage in volts also sometimes displayed as E, U, or emf, I=current in amps, and R=resistance in Ohms. Power is P=V*I, where P=Power in watts, V=Voltage in volts, and I=current in amps.

Let's take an Opti-Par lamped at 575w. Now in the states, our AC is 120v. So, 575w=120v*I or 575w/120v=I and I equals 4.79 amps. So now we go to 120v=4.79a*R or 120v/4.79a=R and R equals 25.05 Ohms. Remember when I said something cold has less resistance, here's where is comes into play. If I take that 25.05 Ohms and divide it by 17, I get 1.47 Ohms, or 1/17th of the lamp's warm resistance. Now, back to our formula: 120v=1.47Ohms*I or 120v/1.47Ohms=I and I equals 81.63 amps. PS, the symbol for Ohms is the Greek sign for Omega, or W in English.

Now the question is, if you have a 20 amp breaker, how come it doesn't trip with 81.63 amps going through it. The reason is the lamp warms up so fast, it doesn't even register. Fluorescents have a longer warm up cycle, about 30 seconds or so. The fluorescent pulls more juice longer. Remember, heat is the enemy, while the heat is power given off, but the heat is caused by current. The more current, the more heat. This is proved easily. Plug in a quad box to the wall with a 20 amp breaker, or even a dimmer with 2400w per channel. Then plug 4 575w lamps into it, provided your power is exactly 120v, if not, 3 will do. Then plug just one into the wall with an extension cord. Let them sit for about 10 minutes or so, then go back and feel the cables. 3 or 4 times the lights, 3 or 4 times the current means much more heat.

Next, remember the turning on/off extremely fast, fluorescents don't like this. They want constant power. The extreme, sudden changes in voltage may damage it because: A) it is designed to work between 100-120v because B) the internal parts are designed to handle a certain amp load and with C) sudden, fast, voltage drops, the light will pull more current to keep working but D) won't trip the breaker because of how fast this is happening all the while E) more heat is generated because there is more current now and finally F) heat is the enemy and what causes things to break.

The UV Wash is 100w. Warning, more algebra ahead: 100w=120v*I or 100w/120v= I and I equals .83 amps vs 100w/90v=I and I equals 1.11 amps. Now, what happens when the voltage drops to 1v, thats 100 amps going through something meant for 1.11 amps at the most. 100x the load. But again, this is happening so fast that breaks won't trip and you won't even see the light turning on and off.

This is why anything that is not a lamp with a filament should be plugged into a normal dimmer.

Now, Pacman, you had mentioned that you had new ETC dimmers. First, ETC is the number one dimmer manufacturer in the world, or at least rated as such. Second, there are Non-dim dimmers that ETC makes. Third, some modern dimmers have a fluorescent setting. Fourth, ETC might now make a dimmer that bypasses the SCR and choke for non-dim mode. Finally, ETC also makes Sine Wave dimmers which actually dim the wave instead of turning it on and off via a SCR circuit, which can safely dim just about anything.

Any more questions? I will be more then happy to answer them. If you haven't figured it out from the past two posts, I am a physics and math junkie. I use this (math and physics) all the time to check power situations, like loading 3000w worth of lights onto a 2400w (20amps at 120v) dimmer and not tripping 15 amp wall breakers.
Last edited by serraava