|
Ask APT
Dear APT;
I have run into a problem and I'm not sure where to go and I though of you. I am using a 4-channel dimmer like an Elation/American DJ. When the dimmer is connected to a 3-watt 120V LED light, like a small flood fixture, the fixture will not go out when the dimmer is at zero. It works fine with a PAR 56. And when they are both connected then both work fine. I checked the voltage with only the LED connected when the dimmer is off and it is at about 80V. With the PAR 56 connected the voltage is 0V when the dimmer is off. It seems that the LED fixture does not have enough load to make the dimmer work. I was thinking of installing a resistor across the line but isn't that a direct short? (Pop goes the resistor?) As a backup I was going to use a 7/15W incandescent lamp and cover it with foil. There has got to be a better way. What would APT do?
P.S. - The show opens in 30 minutes! Please hurry!
Dear Light in the Load,
You've got the right idea - you need a dummy load to make it work. The input impedance of the LED fixture alone is too high to allow the dimmer to drive it correctly.
However, I wonder how you are getting the LED to work with the dimmer in the first place. My guess is that it will eventually cause the dimmer to fail because LEDs are not made to be dimmed by a conventional theatrical dimmer. There are specialized dimmers made for dimming LEDs, like
this one:
But since your show is soon, then you probably need to stick with using a dummy load. A large, high wattage resistor, like a 120-ohm, 150-watt resistor would work, but it's going to get very hot. If you can't find a 150-watt 120-ohm resistor then you could wire several resistors in a combination of series and parallel as long as the
total resistance is about 120 ohms so the current is about 1 amp or less.
Your idea about covering an incandescent lamp with foil is on the right track, but
I would just run long wires to a lamp backstage or in some other hidden place instead of trying to hide it with foil because a lamp covered with foil will get very hot and possibly
shatter.
Good luck and let me know how it works out.
|
 |
|
|
|
|
|
Tool Time for Techs
No self-respecting lighting, audio, or rigging professional would dream of showing up at work without the proper tools. Yet many do it every day. Not only does a tech need a multimeter, a rigger need a harness, and an audio tech needs...what is it that audio techs do again? Nevertheless, there's one vital tool missing from most industry professional's arsenal of work implements, and that's a foundation of understanding the rudimentary principles of the job. But fear not, this short video from the Academy of Production Technology will help you understand two basic concepts. One has to do with a four-letter word that starts with "m" and ends in "ath" and the other is something called power factor. Check out the video at www.APTxl.com.
|
|
Entertainment Electricity Skills Development Webinar
April 5, 12, 19, & 26; 10PM Eastern time/7:00PM West Coast time
Are you preparing to take a certification exam for entertainment electricians and technicians? Could you use some help preparing and practicing with problem solving skills? Then this webinar is for you.
Join ETCP Recognized Trainer Richard Cadena in a series of four one-hour webinars developing problem-solving skills. Each attendee will receive five questions to answer one week ahead of time. A week later, the answers will be reviewed and discussed live online. Attendees will be able to see the explanations drawn onscreen, hear the discussion, and ask questions. All you need is a computer, an internet connection, and a microphone or telephone. (You can call in on a telephone or ask questions using a microphone connected to your computer.)
Can't make one or more of the dates? Not to worry! Each webinar will be recorded and may be viewed by attendees at your own convenience as often as you wish. Click here to sign up.
|
|
Upcoming Classes
Honolulu, HI, March 21-23, 2011
Manila, the Philippines, March 28-30, 2011
Las Vegas, NV, April 11-13, 2011
Orlando, FL, April 18-20, 2011
|
|
|
Sincerely,
Richard Cadena
Academy of Production Technology |
|
|
