DMX 512 Lighting Controll Rob Holter
What is DMX 512? DMX512 stands for digital multiplex512. This means that 512 channels are controlled digitally through 1 data cable. A channel is 1 set of 255 steps that are assigned to control attributes in each light. This may be a color like red, green or blue, and intensity, strobe, pan/tilt or other attributes. All Chains must be terminated!
DMX is: • Serial and asynchronous bitstream. • Delivers 250 kbits/s. • RS-485 physical implementation. • Can have up to 32 nodes on one chain
It starts with the control console (Hog PC) • Generate DMX512 output to control lighting devices • Enable PC control to change dimmer levels • Develop USB platform for future use
DMX Terminator Generel Info A “DMX Terminator” is used when you are using alot of DMX fixtures on one single DMX line (Universe). It removes a lot of noise and flickering on the DMX Tx line which improves the reliability of your fixtures. When a DMX signal has travelled to the end of your DMX line if it is not terminated you get something which is refered to as a “shadow” signal bouncing back along the line which can cause all sorts of problems with you DMX fixtures.The longer the DMX cable run the greater the risk of getting this bounce back.
Cabling • DMX uses a cable consisting of two twisted pairs plus a shield to carry data. The cable must be specifically impedance matched for the digital DMX signal. meaning that microphone cable or other non-rated cable must not be used to carry DMX. Network cable (Cat5, 5e or 6 cable) may be used to carry DMX in an installation; however special consideration must be given to shielding and termination. Under no circumstances should solid core cable like Cat5 be terminated into a screw down connector. • Belden 9729 is a common cable for DMX installation. Other cables may be acceptable; Belden 9729 is a two pair cable, which allows for a spare pair for 'out and back' type terminations if needed. • The original and 1990 versions of the DMX standard specify 120 ohm or 100 ohm 1- or 2-twisted pair shielded cable suitable for use with EIA-485 (120 ohm) and EIA-422 (100 ohm) electronics.
Distribution of DMX • As most theaters have more than one system to run, a DMX universe is usually distributed over the theater via cable and splitters. • A DMX splitter should ideally isolate the separate branch • All branches should be terminated.
DMX Universes • Most newer consoles offer more than one universe of DMX. A universe = 512 Channels! • You may opt to run your LED’s or moving fixtures on a different universe (although you are still restricted by channel count) DMX via Ethernet DMX via 5 Pin
Universes - • Most light boards allow Multiple Universes. • Each Universe can be “split.” • To use a splitter, you will need a DMX out from your board to the splitter.
Digital Theatrical Lighting Console Lights Dimmers Lights splitter DMX512 Lights Dimmers Lights Intelligent Luminaries
Addressing Fixtures • Every fixture will requite a DMX address (1-512). • Addressing procedures will vary by fixture. • The fixture address will match the patch number • This can (and should) be planned ahead of time.
Addressing Fixtures • In some instances, such as cyc lights, you may apply a single address to each of the fixtures. • If you have Cyc lights both on the floor and on a batten, likely you would address them by position. • If you are using a second universe to control your led’s, fixtures will still be addressed 1-512. Your patch will determine which fixtures use the second universe. • You can have several fixtures on the same address – they will all act as one unit (this can be helpful when you are working with Cyc lights).
Once its all hooked together and addressedyou need to worry about Patching • Although the process varies from console to console, you will need to patch the addressed fixtures to your console. • Patching allows you to communicate with the fixture using, on newer consoles, a single channel which then organizes all the fixture attributes and addresses, assigning them to different controllers on the board.
Patching • The patch allows you to communicate with the fixture using the standard protocol of DMX 512. • Everything a fixture does requires at least one channel of DMX • If you have a 96 channel board, you have 96 control channels but still 512 adresses. • This matters because you can run out of communication channels if you are using multiple LED or specialty fixtures that address several DMX addresses per channel!
Patching • At it’s most basic for an LED unit being used RGB, a three color light needs three channels of communication, multiply that by 10 and you have now used 30 channels as opposed to 10 for a conventional fixture. • A moving light can require over 20 channels of communication. • You need to plan your patch way ahead!
Electrical Issues • Although you don’t need more dimmers with adressible units, you still will want dedicated power. • You can select to replace some dimmers with constants (non-dim units) • Limited applications can use “house” electric • LED fixtures pull very low amperage allowing you to daisy chain power as well as data.
Electrical Issues • Example: a 200 watt Altman Spectra Cyc would pull only 1.66 amps (most circuits are 20 amps) Watts/Volts = Amps (Watts = Volts * Amps) • In this case, you could safely run an typical cyc wash of 5 fixtures on 8’ centers on a single circuit.
After its all patched and plugged • Check to see everything functions – trouble shoot immediately! • Watch for data glitches – you need to make sure every branch is terminated. • Be sure to clean up any “spagetti mess” and get the cabling secured from damage or heat. • Back up your patch and show often! • Make sure the back up is on a separate device!
Terminology • Additive Color Mixing: Adding color to create a new color. • Attributes: Any of the functions of a light. This will include pan/tilt, color, iris, shutter, etc. • Beamage: Refers to the visible beam of light in the air. Beamage is increased by the use of hazer or other atmospheric effects. • Block Cue: A cue with all values set to zero. Designed to stop unwanted tracking of values between cues. • Busking: Changing attributes such as color or position “on the fly”. • Color Correction: Changing the color temperature of a lamp by virtue of color media. • CMY Mixing: Subtractive mixing using the secondary colors cyan, magenta and yellow. • Cut Sheet: A data sheet relating to a fixture or other equipment. • Daisy Chain: Connecting fixtures in a series. Fixture one is plugged into fixture two, which is plugged into fixture three, etc. (Can apply to power as well as data) • Dichoric Filter: Color media typically used in moving fixtures. Unlike standard gel, these filters reflect unwanted colors back to the light source rather than absorbing them. • Dimmer Per Circuit: patching dimmer 1 to channel 1, dimmer 2 to channel 2, etc. (1:1) • DMX512: Digital Multiplex. A communications protocol. • DMX Splitter: Splitters are distribution products that provide many outputs from one input to distribute DMX512 to multiple locations such as stage left, stage right, first electric, and dimmer room.
Terminology • Dowser: A mechanical method of creating a black out. Literally, a dowser is placed in front of the light source to create a black out. • Fade: A change in intensity. Fades are generally associated with the beginning or ending of a cue. • Fixture Library: Associated with consoles. A fixture library is the fixture attribute information required for a console and fixture to communicate. • Kelvin. The higher the Kelvin temperature, the “bluer” the appearance of the light. Arc lamps generally function above 5000 degrees Kelvin while conventional lamps are rated around 3200 degrees and appear to be “warmer” in color. • Mark Cue: Creating a blackout before resetting moving lights • Nanometer: A measurement of color within the visible spectrum. • Patch: Assigning a fixture to a channel or a channel to a dimmer. • Palette: A user defined memory featuring color, position, gobos, focus, etc. • Pan: Side to side movement of a fixture. • Parameters: See attributes • Personalities: see attributes • RGB: Red, Green and Blue. The three primary colors of light • SED Curve: Spectral Energy Distribution curve. A graph indicating in nanometers and percentages the colors found in a gel. • Submaster: A specific range of fixtures or attributes pre-assigned by the programmer to a console fader. • Terminator: A DMX plug inserted in the last multi-channel fixture in a universe. • Tilt: Up and Down movement of a fixture. • Tracking: The retention of unchanged values between cues. • Universe: 512 channels of DMX.