Library: DMX, GOBO and Lamp

Library

Lamp, gobo, DMX world

Show control
Hardware
and software
solutions.

DMX world
About DMX,
lamps and
gobos.

T ips&tricks
Some lighting
know how.

Toughts
The impact
of lighting.

LanBox
Just the
facts.

Fixtures
Examples
of modern
fixtures.

Lighting
Some
practical
tips.

The lamp
Why writing an article for a simple lamp? Well, these two lamps (150 HTI and the 200W MSD) are quite unique, special and certainly not simple. Inside each of these lamps, there's not a normal piece of metal wire which starts glowing. Instead, light is generated by means of an arc between two electrodes in a discharge tube which is hermetically sealed from the outside environment. The "cocktail" inside contains rare earth metals, halides, a little bit of mercury and the inert gas Argon in a specific mixture for each lamp. Lots of light: If you think that a 150W or 200W lamp is not much light on your object, you're wrong. Both deliver 96 lumens per Watt. The 200W MSD lamp used in the e.g. Roboscan Pro 518 is expensive, but they will last a long time, produce a lot of light and have a perfect white color.

Gobos
A gobo is the perfect way to project your company or product logo on the wall, on the ceiling, on any surface you want and in any color you want. Gobos are used in intelligent fixtures and can be controlled through DMX. Combined with the other special effects of the fixture you can achieve stunning effects with you logo.

A gobo is a thin, metal (now often glass) plate, with a shape cut out in the center. When it's placed in a light beam, the light can only pass through the cut out shape, making it possible to project that shape on any surface. An obvious usage is to project a company or product logo.

A scanner comes with a number of gobos. These gobos can be used to project dots, stars, triangles and so on. Some fixtures are able to rotate the gobos which add a very special effect.

Design your own gobo!
The gobos of most fixtures are replaceable. Swap the gobos you don't like with other standard gobos, or better, design your own gobo. Designing your own gobos makes it possible to have a gobo of your company logo, of the product logo or any other sign you like. The process is inexpensive and can be done by any supplier of fixture. You only need to have a good drawing.

Rotating gobos
Rotating gobos add a new dimension to the gobo experience. We react to movement, we notice something that is moving sooner that something static. Your company logo turning on the wall or the ceiling of a large exposition is bound to turn some heads.

What on earth is DMX?
In general, professional lighting equipment uses the DMX protocol and network for communication. The DMX network is a reliable, cheap way to control all lights from a DMX controller such as a LanBox. The DMX network consist of shielded twisted pair cables (ordinary balanced microphone cables with 3 pole XLR connectors can be used for a short distance, but is NOT recommended), is easy to install and inexpensive to use. We use the common standard, DMX-512 USITT 1990, usually called DMX for short. Note that not every "DMX" device complies to the standard, see DMX timing.

How does it work?
A DMX network starts with a DMX controller (such as a LanBox). From the controller a DMX cable brings the signal to the first DMX device. Every DMX device has two DMX connectors, one for input and one for output. The DMX cable from the controller is connected to the input connector of the first DMX device. Another DMX cable runs from the output connector of the first DMX device to the input connector of the next one, and so on. At the end of the chain a DMX terminator is placed in the output connector. Most DMX equipment do not come DMX cables or a DMX terminator, so you have to buy them to get going. Each DMX device has an address (ranging from 1 to 512). DMX devices have dip-switches, or other means for setting the DMX address. DMX equipment usually needs a range of addresses, you set the start address of that range. For example our 788-LD+ (the digital dimmer pack) uses 4 DMX addresses. If you want to use two 788-LD+s you can set the first one at address 1 and the next one at address 5. The first one uses addresses 1 through 4 and the second one 5 through 8.

What do I need to know about it?
Basically, almost nothing. All you need to know is described above. Connecting the cables is pretty much self-explanatory. Each DMX device you buy comes with info on how to connect it in the DMX chain, how to set the address and how many addresses it needs. From experience we know that it helps to write down which device uses which addresses.

For more technical information also see: USITT and Ujjal's DMX page.