DMX - Revision history

Lan2u: Mergers

2018-01-18T17:12:18Z

Mergers

← Older revision		Revision as of 17:12, 18 January 2018
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	==Channels==		==Channels==
	The DMX protocol specifies that, on each Universe, there are 512 addressable 'channels'.		The DMX protocol specifies that, in each Universe, there are 512 addressable 'channels'.

	It is standard for each DMX channel to correspond to one attribute. For [[dimmers]], there is only one attribute (brightness), thus these only take a single channel of DMX. More complex lights such as [[:Category:Lighting/Fixtures/Intelligents\|intelligent lights]] have more attributes that can be changed - for example Dimmer, Shutter, Pan, Tilt, Colour, etc - and therefore use up more than one channel. Each fixture will be assigned a "start address" - the first DMX channel it will listen for. Multiple fixtures can be set to listen to the same start address to save channels - though care should be used to ensure they are of the same type (or use the same set of channels - this information can be found in the fixture manual or on the fixture's Wiki page).		It is standard for each DMX channel to correspond to one attribute. For [[dimmers]], there is only one attribute (brightness), thus these only take a single channel of DMX. More complex lights such as [[:Category:Lighting/Fixtures/Intelligents\|intelligent lights]] have more attributes that can be changed - for example, Dimmer, Shutter, Pan, Tilt, Colour, etc - and therefore use up more than one channel. Each fixture will be assigned a "start address" - the first DMX channel it will listen for. Multiple fixtures can be set to listen to the same start address to save channels - though care should be used to ensure they are of the same type (or use the same set of channels - this information can be found in the fixture manual or on the fixture's Wiki page).

	Each channel has 255 levels. The level is best thought of as "how much you put the fader up", so for example, if channel 1 was for a [[Profile]], 0 would give no light, 25 would be approximately 10% brightness, 128 would be 50% brightness, and 255 would be 100% brightness. On most consoles, these levels will be shown only as percentages (with "FF" or "FL" often meaning 100%).		Each channel has 255 levels. The level is best thought of as "how much you put the fader up", so for example, if channel 1 was for a [[Profile]], 0 would give no light, 25 would be approximately 10% brightness, 128 would be 50% brightness, and 255 would be 100% brightness. On most consoles, these levels will be shown only as percentages (with "FF" or "FL" often meaning 100%).

	==Universes==		==Universes==
	A set of devices listening to one DMX signal is referred to as a ''Universe''. The DMX Universe is constructed by daisy chaining devices together. The DMX Standard instructs us to chain no more than 32 devices together (without a DMX amplifier/booster), though the non-perfect conditions in [[Venue 1]] reduces this to roughly 20.		A set of devices listening to one DMX signal is referred to as a ''Universe''. The DMX Universe is constructed by daisy-chaining devices together. The DMX Standard instructs us to chain no more than 32 devices together (without a DMX amplifier/booster), though the non-perfect conditions in [[Venue 1]] reduces this to roughly 20.

	Multiple universes can be used to allow consoles, such as the [[Pearl]], to control more fixtures than will fit in one universe. A typical use of this in Venue 1 is to attach the [[Dimmers]] to one universe and the [[Optosplitter]] for the Intelligent Heads on the [[Octagon]] on another. In fact, the Pearl allows the use of multiple universes on 1 cable (see the section on [[DMX#Cables\|cables]] below).		Multiple universes can be used to allow consoles, such as the [[Pearl]], to control more fixtures than will fit in one universe. A typical use of this in Venue 1 is to attach the [[Dimmers]] to one universe and the [[Optosplitter]] for the Intelligent Heads on the [[Octagon]] on another. In fact, the Pearl allows the use of multiple universes on 1 cable (see the section on [[DMX#Cables\|cables]] below).
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	The DMX data path must be ''terminated'' at both ends to prevent information from "bouncing" back down the cable and creating interference. One of these terminators is built into the lighting desk, while one must be attached to the output of the last device in the chain.		The DMX data path must be ''terminated'' at both ends to prevent information from "bouncing" back down the cable and creating interference. One of these terminators is built into the lighting desk, while one must be attached to the output of the last device in the chain.

	Some intelligent lights and dimmers have terminators built ~~in to~~ them, whilst others do not - if you are not sure, you should attach a terminator anyway.		Some intelligent lights and dimmers have terminators built into them, whilst others do not - if you are not sure, you should attach a terminator anyway.

	The terminator itself is simply a 120ohm, 0.5W resistor across cores 2 and 3 (and possibly 4 and 5) of the cable (see below).		The terminator itself is simply a 120ohm, 0.5W resistor across cores 2 and 3 (and possibly 4 and 5) of the cable (see below).

			==Mergers==
			In the usual setup 1 DMX controller controls multiple different universes of DMX connections. It is possible however to control the same set of lights at the same time using 2 different controllers. This cannot however simply be done by connecting 2 DMX controllers to the same network as this will cause inconsistencies as one controller will think a DMX device is doing 1 thing while the other controller will think it is doing something else. To solve this problem a DMX merger is usually required. This merger allows the merging of multiple input DMX signals (>2) into an output signal depending on well-defined rules such as highest takes priority.

	==Cables==		==Cables==

Angus Ireland: /* Cables */

2014-04-12T12:21:40Z

Cables

← Older revision		Revision as of 12:21, 12 April 2014
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	==Cables==		==Cables==
	[[File:XLR5_pinouts.svg\|thumb\|right\|XLR5 pinouts]]		[[File:XLR5_pinouts.svg\|thumb\|right\|XLR5 pinouts]]
	There is technically no such thing as a ''DMX cable'' or connector. Instead, we use [[Cables & Connectors/XLR\|XLR]] cables which are usually thinner (and of lower resistance) than the ones we use for sound. ~~The ''DMX Standard'' specifies~~ that we ~~should~~ use five-pin XLR, or XLR5, though many manufacturers use non-~~standard~~ connections (see below).		There is technically no such thing as a ''DMX cable'' or connector. Instead, we usually use [[Cables & Connectors/XLR\|XLR]] cables which are usually thinner (and of lower resistance) than the ones we use for sound. Convention tends to be that we use five-pin XLR, or XLR5, though many manufacturers use non-conventional connections (see below).

	Typically, DMX cables have three cores: one '''ground''' (Pin 1) and a ''twisted pair bus'' with one '''hot''' (+ve, pin 3) and one '''cold''' (-ve, pin 2) wire. Pins 4 (-ve) and 5 (+ve) are a spare bus and are sometimes used to carry a second universe on the same cable. (The latter two cores should be used with care, for example on the Pearl ~~outputs~~, as some manufacturers have used these cores for power.)		Typically, DMX cables have three cores: one '''ground''' (Pin 1) and a ''twisted pair bus'' with one '''hot''' (+ve, pin 3) and one '''cold''' (-ve, pin 2) wire. Pins 4 (-ve) and 5 (+ve) are a spare bus and are sometimes used to carry a second universe on the same cable. (The latter two cores should be used with care - for example the Pearl may use this second universe feature, but some manufacturers have used these cores for power.)

	==Technical Information==		==Technical Information==

Angus Ireland: /* Cables */

2013-08-27T20:01:11Z

Cables

← Older revision		Revision as of 20:01, 27 August 2013
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	==Cables==		==Cables==
	[[File:XLR5_pinouts.svg\|thumb\|right\|XLR5 pinouts]]		[[File:XLR5_pinouts.svg\|thumb\|right\|XLR5 pinouts]]
	There is technically no such thing as a ''DMX cable'' or connector. Instead, we use [[Cables & Connectors/XLR\|XLR]] cables which are usually thinner than the ones we use for sound. The ''DMX Standard'' specifies that we should use five-pin XLR, or XLR5, though many manufacturers use non-standard connections (see below).		There is technically no such thing as a ''DMX cable'' or connector. Instead, we use [[Cables & Connectors/XLR\|XLR]] cables which are usually thinner (and of lower resistance) than the ones we use for sound. The ''DMX Standard'' specifies that we should use five-pin XLR, or XLR5, though many manufacturers use non-standard connections (see below).

	Typically, DMX cables have three cores: one '''ground''' (Pin 1) and a ''twisted pair bus'' with one '''hot''' (+ve, pin 3) and one '''cold''' (-ve, pin 2) wire. Pins 4 (-ve) and 5 (+ve) are a spare bus and are sometimes used to carry a second universe on the same cable. (The latter two cores should be used with care, for example on the Pearl outputs, as some manufacturers have used these cores for power.)		Typically, DMX cables have three cores: one '''ground''' (Pin 1) and a ''twisted pair bus'' with one '''hot''' (+ve, pin 3) and one '''cold''' (-ve, pin 2) wire. Pins 4 (-ve) and 5 (+ve) are a spare bus and are sometimes used to carry a second universe on the same cable. (The latter two cores should be used with care, for example on the Pearl outputs, as some manufacturers have used these cores for power.)

Angus Ireland at 18:54, 28 May 2013

2013-05-28T18:54:40Z

← Older revision		Revision as of 18:54, 28 May 2013
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	The DMX protocol specifies that, on each Universe, there are 512 addressable 'channels'.		The DMX protocol specifies that, on each Universe, there are 512 addressable 'channels'.

	It is standard for each DMX channel to correspond to one attribute. For [[dimmers]], there is only one attribute (brightness), thus these only take a single channel of DMX. More complex lights such as [[Category:Lighting/Fixtures/Intelligents\|intelligent lights]] have more attributes that can be changed - for example Dimmer, Shutter, Pan, Tilt, Colour, etc - and therefore use up more than one channel. Each fixture will be assigned a "start address" - the first DMX channel it will listen for. Multiple fixtures can be set to listen to the same start address to save channels - though care should be used to ensure they are of the same type (or use the same set of channels - this information can be found in the fixture manual or on the fixture's Wiki page).		It is standard for each DMX channel to correspond to one attribute. For [[dimmers]], there is only one attribute (brightness), thus these only take a single channel of DMX. More complex lights such as [[:Category:Lighting/Fixtures/Intelligents\|intelligent lights]] have more attributes that can be changed - for example Dimmer, Shutter, Pan, Tilt, Colour, etc - and therefore use up more than one channel. Each fixture will be assigned a "start address" - the first DMX channel it will listen for. Multiple fixtures can be set to listen to the same start address to save channels - though care should be used to ensure they are of the same type (or use the same set of channels - this information can be found in the fixture manual or on the fixture's Wiki page).

	Each channel has 255 levels. The level is best thought of as "how much you put the fader up", so for example, if channel 1 was for a [[Profile]], 0 would give no light, 25 would be approximately 10% brightness, 128 would be 50% brightness, and 255 would be 100% brightness. On most consoles, these levels will be shown only as percentages (with "FF" or "FL" often meaning 100%).		Each channel has 255 levels. The level is best thought of as "how much you put the fader up", so for example, if channel 1 was for a [[Profile]], 0 would give no light, 25 would be approximately 10% brightness, 128 would be 50% brightness, and 255 would be 100% brightness. On most consoles, these levels will be shown only as percentages (with "FF" or "FL" often meaning 100%).

Campbell Anderson: /* Channels */

2013-05-28T17:26:21Z

Channels

← Older revision		Revision as of 17:26, 28 May 2013
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	It is standard for each DMX channel to correspond to one attribute. For [[dimmers]], there is only one attribute (brightness), thus these only take a single channel of DMX. More complex lights such as [[Category:Lighting/Fixtures/Intelligents\|intelligent lights]] have more attributes that can be changed - for example Dimmer, Shutter, Pan, Tilt, Colour, etc - and therefore use up more than one channel. Each fixture will be assigned a "start address" - the first DMX channel it will listen for. Multiple fixtures can be set to listen to the same start address to save channels - though care should be used to ensure they are of the same type (or use the same set of channels - this information can be found in the fixture manual or on the fixture's Wiki page).		It is standard for each DMX channel to correspond to one attribute. For [[dimmers]], there is only one attribute (brightness), thus these only take a single channel of DMX. More complex lights such as [[Category:Lighting/Fixtures/Intelligents\|intelligent lights]] have more attributes that can be changed - for example Dimmer, Shutter, Pan, Tilt, Colour, etc - and therefore use up more than one channel. Each fixture will be assigned a "start address" - the first DMX channel it will listen for. Multiple fixtures can be set to listen to the same start address to save channels - though care should be used to ensure they are of the same type (or use the same set of channels - this information can be found in the fixture manual or on the fixture's Wiki page).

	Each channel has 255 levels. The level is best thought of as "how much you put the fader up", so for example, if channel 1 was for a [[Profile]], 0 would give no light, 25 would be approximately 10% brightness, ~~124~~ would be 50% brightness, and 255 would be 100% brightness. On most consoles, these levels will be shown only as percentages (with "FF" or "FL" often meaning 100%).		Each channel has 255 levels. The level is best thought of as "how much you put the fader up", so for example, if channel 1 was for a [[Profile]], 0 would give no light, 25 would be approximately 10% brightness, 128 would be 50% brightness, and 255 would be 100% brightness. On most consoles, these levels will be shown only as percentages (with "FF" or "FL" often meaning 100%).

	==Universes==		==Universes==

Angus Ireland at 17:09, 28 May 2013

2013-05-28T17:09:46Z

← Older revision		Revision as of 17:09, 28 May 2013
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	The DMX protocol specifies that, on each Universe, there are 512 addressable 'channels'.		The DMX protocol specifies that, on each Universe, there are 512 addressable 'channels'.

	It is standard for each DMX channel to correspond to one attribute. For [[dimmers]], there is only one attribute (brightness), thus these only take a single channel of DMX. More complex lights such as [[Category:Lighting/Fixtures/Intelligents\|intelligent lights]] have more attributes that can be changed - for example Dimmer, Shutter, Pan, Tilt, Colour, etc - and therefore use up more than one channel. Each fixture will be assigned a "start address" - the first DMX channel it will listen for. Multiple ~~fxitures~~ can be set to listen to the same start address to save channels - though care should be used to ensure they are of the same type (or use the same set of channels - this information can be found in the fixture manual or on the fixture's Wiki page).		It is standard for each DMX channel to correspond to one attribute. For [[dimmers]], there is only one attribute (brightness), thus these only take a single channel of DMX. More complex lights such as [[Category:Lighting/Fixtures/Intelligents\|intelligent lights]] have more attributes that can be changed - for example Dimmer, Shutter, Pan, Tilt, Colour, etc - and therefore use up more than one channel. Each fixture will be assigned a "start address" - the first DMX channel it will listen for. Multiple fixtures can be set to listen to the same start address to save channels - though care should be used to ensure they are of the same type (or use the same set of channels - this information can be found in the fixture manual or on the fixture's Wiki page).

	Each channel has 255 levels. The level is best thought of as "how much you put the fader up", so for example, if channel 1 was for a [[Profile]], 0 would give no light, 25 would be approximately 10% brightness, 124 would be 50% brightness, and 255 would be 100% brightness. On most consoles, these levels will be shown only as percentages (with "FF" or "FL" often meaning 100%).		Each channel has 255 levels. The level is best thought of as "how much you put the fader up", so for example, if channel 1 was for a [[Profile]], 0 would give no light, 25 would be approximately 10% brightness, 124 would be 50% brightness, and 255 would be 100% brightness. On most consoles, these levels will be shown only as percentages (with "FF" or "FL" often meaning 100%).
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	*DMX has no error correction: thus any interference will not be detected by the fixture. Poor cabling will increase this interference, causing the lights to behave erratically or fail to respond completely. For this reason, "critical" controls, such as for moving rigs or pyrotechnics, should ''never'' be controlled using DMX.		*DMX has no error correction: thus any interference will not be detected by the fixture. Poor cabling will increase this interference, causing the lights to behave erratically or fail to respond completely. For this reason, "critical" controls, such as for moving rigs or pyrotechnics, should ''never'' be controlled using DMX.

	*DMX is a multiplexed system: unlike a serial system which may only send data when the lighting state changes (i.e. if a fixture misses a state change then it will hold the previous state until the next state change), DMX constantly sends the state up to thirty times a second. If the link from the desk to a fixture is broken, then the fixture will hold the last state~~, but~~ as soon as the link is restored, the current state will be read by the lamp. (A useful note: if the lighting desk fails, then unplug the cables from the back to hold the present state, restart the lighting desk, set the state and then reconnect the cables. This will prevent a black out when the desk is reset.)		*DMX is a multiplexed system: unlike a serial system which may only send data when the lighting state changes (i.e. if a fixture misses a state change then it will hold the previous state until the next state change), DMX constantly sends the state up to thirty times a second. If the link from the desk to a fixture is broken, then the fixture will usually hold the last state. Beware that as soon as the link is restored, the current state will be read by the lamp, even if it is completely different. (A useful note: if the lighting desk fails, then unplug the cables from the back to hold the present state, restart the lighting desk, set the state and then reconnect the cables. This will prevent a black out when the desk is reset.)

Angus Ireland: /* Channels */

2013-05-28T17:08:20Z

Channels

← Older revision		Revision as of 17:08, 28 May 2013
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	The DMX protocol specifies that, on each Universe, there are 512 addressable 'channels'.		The DMX protocol specifies that, on each Universe, there are 512 addressable 'channels'.

	It is standard for each DMX channel to correspond to one attribute. For [[dimmers]], there is only one attribute (brightness), thus these only take a single channel of DMX. More complex lights such as [[Lighting/Fixtures/Intelligents\|intelligent lights]] have more attributes that can be changed - for example Dimmer, Shutter, Pan, Tilt, Colour, etc - and therefore use up more than one channel. Each fixture will be assigned a "start address" - the first DMX channel it will listen for. Multiple fxitures can be set to listen to the same start address to save channels - though care should be used to ensure they are of the same type (or use the same set of channels - this information can be found in the fixture manual or on the fixture's Wiki page).		It is standard for each DMX channel to correspond to one attribute. For [[dimmers]], there is only one attribute (brightness), thus these only take a single channel of DMX. More complex lights such as [[Category:Lighting/Fixtures/Intelligents\|intelligent lights]] have more attributes that can be changed - for example Dimmer, Shutter, Pan, Tilt, Colour, etc - and therefore use up more than one channel. Each fixture will be assigned a "start address" - the first DMX channel it will listen for. Multiple fxitures can be set to listen to the same start address to save channels - though care should be used to ensure they are of the same type (or use the same set of channels - this information can be found in the fixture manual or on the fixture's Wiki page).

	Each channel has 255 levels. The level is best thought of as "how much you put the fader up", so for example, if channel 1 was for a [[Profile]], 0 would give no light, 25 would be approximately 10% brightness, 124 would be 50% brightness, and 255 would be 100% brightness. On most consoles, these levels will be shown only as percentages (with "FF" or "FL" often meaning 100%).		Each channel has 255 levels. The level is best thought of as "how much you put the fader up", so for example, if channel 1 was for a [[Profile]], 0 would give no light, 25 would be approximately 10% brightness, 124 would be 50% brightness, and 255 would be 100% brightness. On most consoles, these levels will be shown only as percentages (with "FF" or "FL" often meaning 100%).


	==Universes==		==Universes==

Angus Ireland at 17:07, 28 May 2013

2013-05-28T17:07:35Z

← Older revision		Revision as of 17:07, 28 May 2013
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	Digital Multiplex (DMX or USITT DMX512-A) is the industry standard lighting control protocol, and the protocol used in the union.		Digital Multiplex (DMX or USITT DMX512-A) is the industry standard lighting control protocol, and the protocol used in the union.
	__TOC__		__TOC__

			==Channels==
			The DMX protocol specifies that, on each Universe, there are 512 addressable 'channels'.

			It is standard for each DMX channel to correspond to one attribute. For [[dimmers]], there is only one attribute (brightness), thus these only take a single channel of DMX. More complex lights such as [[Lighting/Fixtures/Intelligents\|intelligent lights]] have more attributes that can be changed - for example Dimmer, Shutter, Pan, Tilt, Colour, etc - and therefore use up more than one channel. Each fixture will be assigned a "start address" - the first DMX channel it will listen for. Multiple fxitures can be set to listen to the same start address to save channels - though care should be used to ensure they are of the same type (or use the same set of channels - this information can be found in the fixture manual or on the fixture's Wiki page).

			Each channel has 255 levels. The level is best thought of as "how much you put the fader up", so for example, if channel 1 was for a [[Profile]], 0 would give no light, 25 would be approximately 10% brightness, 124 would be 50% brightness, and 255 would be 100% brightness. On most consoles, these levels will be shown only as percentages (with "FF" or "FL" often meaning 100%).


	==Universes==		==Universes==
	A DMX Universe ~~consists of 512 control channels or "addresses"~~. ~~Each device which receives~~ DMX is ~~given an address - or start address~~, ~~if multiple channels are used~~ - to ~~listen to for control information, such as intensity, position, colour, speed, etc~~.		A set of devices listening to one DMX signal is referred to as a ''Universe''. The DMX Universe is constructed by daisy chaining devices together. The DMX Standard instructs us to chain no more than 32 devices together (without a DMX amplifier/booster), though the non-perfect conditions in [[Venue 1]] reduces this to roughly 20.

	The DMX Universe is constructed by daisy chaining devices together. The DMX Standard instructs us to chain no more than 32 devices together (without a DMX amplifier/booster), though the non-perfect conditions in [[Venue 1]] reduces this to roughly 20.		Multiple universes can be used to allow consoles, such as the [[Pearl]], to control more fixtures than will fit in one universe. A typical use of this in Venue 1 is to attach the [[Dimmers]] to one universe and the [[Optosplitter]] for the Intelligent Heads on the [[Octagon]] on another. In fact, the Pearl allows the use of multiple universes on 1 cable (see the section on [[DMX#Cables\|cables]] below).

	Multiple universes can be used to allow consoles, such as the [[Pearl]], to control more fixtures than will fit in one universe. A typical use of this in Venue 1 is to attach the [[Dimmers]] to one universe and the [[Optosplitter]] for the ~~[[Lighting/Fixtures/Intelligents\|~~Intelligent Heads]] on the [[Octagon]] on another.

	==Terminators==		==Terminators==
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	The lighting desk sends up to thirty packets of 512 bytes in length each second, allowing for thirty updates of the lighting state per second. Each of the 512 bytes is a DMX channel and are numbered from 1 (first byte sent) to 512 (last byte sent). Each channel has 256 values (0-255). Some devices use 16 bits for pan, tilt, etc: these are sent using two DMX channels.		The lighting desk sends up to thirty packets of 512 bytes in length each second, allowing for thirty updates of the lighting state per second. Each of the 512 bytes is a DMX channel and are numbered from 1 (first byte sent) to 512 (last byte sent). Each channel has 256 values (0-255). Some devices use 16 bits for pan, tilt, etc: these are sent using two DMX channels.

			==Non-standard connectors==
	It is standard for each DMX channel to correspond to one attribute. For dimmers, there is only one attribute (brightness), thus these only take a single channel of DMX. More complex lights such as intelligent lights have more attributes that can be changed. For example, Dimmer, Shutter, Pan, Tilt, Colour, Gobo, Gobo Spin, Prism, Strike/Reset/Lamp Off, Frost, etc. What each channel corresponds to can often be found in the fixture manual

	Each channel has 255 levels. The level is best thought of as "how much you put the fader up", so for example, if channel 1 was for a [[Profile]], 0 would give no light, 25 degrees would be aprox 10% brightness, 124 would be aprox 50% brightness, and 255 would be 100% brightness.

	The [[Pearl]] has 4 main DMX outputs that we use in two pairs of XLR5 outputs (1&3, 2&4). This gives out signal on all 5 pins (i.e for 1&3, the first bus is universe 1, the second bus is universe 3). Since our 5 pin cable is mostly 3 core, to use Universes 3 or 4 requires use of a DMX Y-split. This Takes one XLR5 5-core input (from the Pearl), and gives out two 3-core XLR5 DMX outputs (one for the first bus, one for the bus). For one output, it will put cold (pin 2) and hot (pin 3), onto cold (pin 2) and hot (pin 3), for the other output, it will put cold (pin 4) and hot (pin 5) onto cold (pin 2) and hot (pin 5).

	~~<h2>~~Non-standard connectors~~</h2>~~

	Some equipment does not conform to the standard XLR5 connectors, instead using XLR3 or XLR4 connectors.		Some equipment does not conform to the standard XLR5 connectors, instead using XLR3 or XLR4 connectors.

	XLR3 connectors normally use the same pins as XLR5, except for Martin (518s, 812s, 1220s, etc.) ~~fixtures~~ which have swapped the purpose of pins 2 and 3 (i.e. cold and hot). ~~Therefore~~, a pin swap is needed ~~for each change of Martin fixture~~. These can be found in the Ents ~~cupboard~~. Note that pin swaps need to be used in pairs - one to ~~change~~ the signal ~~for the~~ Martin ~~fixture~~, one to change it back for ~~the~~ other fixtures. Sound cables also use XLR3 connectors: these should not be used in place of genuine DMX cables as they do not have a twisted core. Similarly, DMX cables should not be used in place of sound cables.		XLR3 connectors normally use the same pins as XLR5, except for most Martin fixtures (518s, 812s, 1220s, etc), which have swapped the purpose of pins 2 and 3 (i.e. cold and hot) for historical reasons. To use these Martin fixtures, a ''pin-swap'' is needed.. These can be found in the [[Ents Cupboard]]. Note that, unless the only fixtures in the chain are Martin fixtures, pin swaps need to be used in pairs - one before the fixture to swap the signal to Martin-mode, and one to change it back for other fixtures.

	XLR4 is used for the scroller units. A control box above the ~~Octogon~~ converts the XLR5 system to the XLR4 system for the scrollers. The scrollers are connected in a ring (using XLR4 cable) back to the control box.		XLR4 is used for the [[Scrollers\|scroller]] units. A control box above the Octagon converts the XLR5 system to the XLR4 system for the scrollers. The scrollers are connected in a ring (using XLR4 cable) back to the control box.

	A summary of DMX connectors in our venue is given below:		A summary of DMX connectors in our venue is given below:
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	\|DMX standard (XLR5)\|\|Ground\|\|Data -ve\|\|Data +ve\|\|Spare -ve\|\|Spare +ve		\|DMX standard (XLR5)\|\|Ground\|\|Data -ve\|\|Data +ve\|\|Spare -ve\|\|Spare +ve
	\|-		\|-
	\|XLR4 (Scrollers)\|\|Ground\|\|Data -ve\|\|Data +ve\|\|Power +24V\|\|		\|XLR4 (Scrollers)\|\|Ground\|\|Data -ve\|\|Data +ve\|\|Power +24V
			\|style="text-align:center"\| -
	\|-		\|-
	\|XLR3 (except Martin)\|\|Ground\|\|Data -ve\|\|Data +ve\|\| \|\|		\|XLR3 (except Martin)\|\|Ground\|\|Data -ve\|\|Data +ve
			\|style="text-align:center"\| -
			\|style="text-align:center"\| -
	\|-		\|-
	\|XLR3 (Martin)\|\|Ground\|\|Data +ve\|\|Data -ve\|\| \|\|		\|XLR3 (Martin)\|\|Ground\|\|Data +ve\|\|Data -ve
			\|style="text-align:center"\| -
			\|style="text-align:center"\| -
	\|}		\|}

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	*RS-485 (serial protocol underneath DMX) is a bus system. This means that all fixtures read the same signal regardless of position on the bus. Hence lights can be placed in any order on any DMX universe.		*RS-485 (serial protocol underneath DMX) is a bus system. This means that all fixtures read the same signal regardless of position on the bus. Hence lights can be placed in any order on any DMX universe.

	*DMX has no error correction: thus any interference will not be detected by the fixture. Poor cabling will increase this interference, causing the lights to behave erratically. ~~Also~~, moving rigs or pyrotechnics should ~~not~~ be controlled using DMX.		*DMX has no error correction: thus any interference will not be detected by the fixture. Poor cabling will increase this interference, causing the lights to behave erratically or fail to respond completely. For this reason, "critical" controls, such as for moving rigs or pyrotechnics, should ''never'' be controlled using DMX.

	*DMX is a multiplexed system: unlike a serial system which may only send data when the lighting state changes (i.e. if a fixture misses a state change then it will hold the previous state until the next state change), DMX constantly sends the state up to thirty times a second. If the link from the desk to a fixture is broken, then the fixture will hold the last state, but as soon as the link is restored, the current state will be read by the lamp. (A useful note: if the lighting desk fails, then unplug the cables from the back to hold the present state, restart the lighting desk, set the state and then reconnect the cables. This will prevent a black out when the desk is reset.)		*DMX is a multiplexed system: unlike a serial system which may only send data when the lighting state changes (i.e. if a fixture misses a state change then it will hold the previous state until the next state change), DMX constantly sends the state up to thirty times a second. If the link from the desk to a fixture is broken, then the fixture will hold the last state, but as soon as the link is restored, the current state will be read by the lamp. (A useful note: if the lighting desk fails, then unplug the cables from the back to hold the present state, restart the lighting desk, set the state and then reconnect the cables. This will prevent a black out when the desk is reset.)

Angus Ireland at 16:12, 28 May 2013

2013-05-28T16:12:53Z

← Older revision		Revision as of 16:12, 28 May 2013
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	Digital Multiplex (DMX or USITT DMX512-A) is the industry standard lighting control protocol, and the protocol used in the union. ~~The standard only specifies one type of connector (XLR5), although other non-standard connectors have been used by many lighting manufacturers (see below).~~		Digital Multiplex (DMX or USITT DMX512-A) is the industry standard lighting control protocol, and the protocol used in the union.
			__TOC__

	DMX ~~cables have three cores: one ground (pin 1) and a twisted pair bus with one hot (+ve, pin 3) and one cold (~~-ve, ~~pin 2) wire. Pins 4 (-ve) and 5 (+ve)~~ are ~~a spare bus and may be~~ used for ~~a second universe on the same cable. (The latter two cores should be used with care~~, ~~for example on the Pearl outputs~~, ~~as some manufacturers have used these cores for power~~.)		==Universes==
			A DMX Universe consists of 512 control channels or "addresses". Each device which receives DMX is given an address - or start address, if multiple channels are used - to listen to for control information, such as intensity, position, colour, speed, etc.

	~~Each bus used a RS-485 serial protocol which must be terminated at each end, one of which~~ is ~~inside the lighting desk (or DMX splitter)~~. The ~~terminators are required~~ to ~~stop the signal bouncing back at the end of the cable~~ (~~and interfering with the signal~~)~~. The lighting desk sends up to thirty packets of 512 bytes in length each second~~, ~~allowing for thirty updates of~~ the ~~lighting state per second. Each of the 512 bytes is a DMX channel and are numbered from~~ 1 ~~(first byte sent)~~ to ~~512 (last byte sent). Each channel has 256 values (0-255). Some devices use 16 bits for pan, tilt, etc.: these are sent using two DMX channels~~.		The DMX Universe is constructed by daisy chaining devices together. The DMX Standard instructs us to chain no more than 32 devices together (without a DMX amplifier/booster), though the non-perfect conditions in [[Venue 1]] reduces this to roughly 20.

	~~Each~~ universe ~~is often a cable run~~. ~~For example, a common configuration~~ in Venue 1 is ~~for Universe 1~~ to be the ~~Dimmer Racks, Universe 2~~ to be the Intelligent ~~lights~~ on the ~~octagon~~ and ~~above~~ the ~~floor~~, and ~~Universe~~ 3 for ~~anything on stage~~. ~~Each~~ universe ~~could link to several fixtures:~~ the ~~standard allows~~ for 32, ~~although~~ the ~~non~~-~~perfect conditions~~ in ~~Venue~~ 1 ~~reduces this~~ to 20 (~~without a~~ DMX ~~amplifier/booster)~~.		Multiple universes can be used to allow consoles, such as the [[Pearl]], to control more fixtures than will fit in one universe. A typical use of this in Venue 1 is to attach the [[Dimmers]] to one universe and the [[Optosplitter]] for the [[Lighting/Fixtures/Intelligents\|Intelligent Heads]] on the [[Octagon]] on another.

			==Terminators==
			The DMX data path must be ''terminated'' at both ends to prevent information from "bouncing" back down the cable and creating interference. One of these terminators is built into the lighting desk, while one must be attached to the output of the last device in the chain.

			Some intelligent lights and dimmers have terminators built in to them, whilst others do not - if you are not sure, you should attach a terminator anyway.

			The terminator itself is simply a 120ohm, 0.5W resistor across cores 2 and 3 (and possibly 4 and 5) of the cable (see below).

			==Cables==
			[[File:XLR5_pinouts.svg\|thumb\|right\|XLR5 pinouts]]
			There is technically no such thing as a ''DMX cable'' or connector. Instead, we use [[Cables & Connectors/XLR\|XLR]] cables which are usually thinner than the ones we use for sound. The ''DMX Standard'' specifies that we should use five-pin XLR, or XLR5, though many manufacturers use non-standard connections (see below).

			Typically, DMX cables have three cores: one '''ground''' (Pin 1) and a ''twisted pair bus'' with one '''hot''' (+ve, pin 3) and one '''cold''' (-ve, pin 2) wire. Pins 4 (-ve) and 5 (+ve) are a spare bus and are sometimes used to carry a second universe on the same cable. (The latter two cores should be used with care, for example on the Pearl outputs, as some manufacturers have used these cores for power.)

			==Technical Information==
			Each bus uses the RS-485 serial protocol which must be terminated at each end.

			The lighting desk sends up to thirty packets of 512 bytes in length each second, allowing for thirty updates of the lighting state per second. Each of the 512 bytes is a DMX channel and are numbered from 1 (first byte sent) to 512 (last byte sent). Each channel has 256 values (0-255). Some devices use 16 bits for pan, tilt, etc: these are sent using two DMX channels.

	Each fixture will have a DMX Address. This is the first DMX channel that it reads. The number of channels it reads depends on what mode it is set to, and how many channels that mode takes up. For example, an Alpha Wash takes up 17 channels. If it is given address 10, it will read channels 10-26. (N.B. The next free address is 10+17 = 27.)

	It is standard for each DMX channel to correspond to one attribute. For dimmers, there is only one attribute (brightness), thus these only take a single channel of DMX. More complex lights such as intelligent lights have more attributes that can be changed. For example, Dimmer, Shutter, Pan, Tilt, Colour, Gobo, Gobo Spin, Prism, Strike/Reset/Lamp Off, Frost, etc. What each channel corresponds to can often be found in the fixture manual		It is standard for each DMX channel to correspond to one attribute. For dimmers, there is only one attribute (brightness), thus these only take a single channel of DMX. More complex lights such as intelligent lights have more attributes that can be changed. For example, Dimmer, Shutter, Pan, Tilt, Colour, Gobo, Gobo Spin, Prism, Strike/Reset/Lamp Off, Frost, etc. What each channel corresponds to can often be found in the fixture manual
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	\|}		\|}

	~~<h2>~~Problems~~</h2>~~		==Problems==

	*DMX is a one-way protocol: the lighting desk sends instructions to the lights and no information is sent back. Thus the lighting desk does not know if the lights have power, are working, etc..		*DMX is a one-way protocol: the lighting desk sends instructions to the lights and no information is sent back. Thus the lighting desk does not know if the lights have power, are working, etc..

Campbell Anderson at 09:19, 26 May 2013

2013-05-26T09:19:07Z

← Older revision		Revision as of 09:19, 26 May 2013
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	A summary of DMX connectors in our venue is given below:		A summary of DMX connectors in our venue is given below:

	\|\|Type\|Pin 1\|Pin 2\|Pin 3\|Pin 4\|Pin 5		{\| class="wikitable"
	DMX standard\|Ground\|Data -ve\|Data +ve\|Spare -ve\|Spare +ve		\|-
	XLR4 (Scrollers)\|Ground\|Data -ve\|Data +ve\|Power +24V\|		!Type !! Pin 1 !! Pin 2 !! Pin 3 !! Pin 4 !! Pin 5
	XLR3 (except Martin)\|Ground\|Data -ve\|Data +ve\| \|		\|-
	XLR3 (Martin)\|Ground\|Data +ve\|Data -ve\| \| \|\|		\|DMX standard (XLR5)\|\|Ground\|\|Data -ve\|\|Data +ve\|\|Spare -ve\|\|Spare +ve
			\|-
			\|XLR4 (Scrollers)\|\|Ground\|\|Data -ve\|\|Data +ve\|\|Power +24V\|\|
			\|-
			\|XLR3 (except Martin)\|\|Ground\|\|Data -ve\|\|Data +ve\|\| \|\|
			\|-
			\|XLR3 (Martin)\|\|Ground\|\|Data +ve\|\|Data -ve\|\| \|\|
			\|}

	<h2>Problems</h2>		<h2>Problems</h2>
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	*DMX has no error correction: thus any interference will not be detected by the fixture. Poor cabling will increase this interference, causing the lights to behave erratically. Also, moving rigs or pyrotechnics should not be controlled using DMX.		*DMX has no error correction: thus any interference will not be detected by the fixture. Poor cabling will increase this interference, causing the lights to behave erratically. Also, moving rigs or pyrotechnics should not be controlled using DMX.

	*DMX is a multiplexed system: unlike a serial system which may only send data when the lighting state changes (i.e. if a fixture misses a state change then it will hold the previous state until the next state change), DMX constantly sends the state up to thirty times a ~~minute~~. If the link from the desk to a fixture is broken, then the fixture will hold the last state, but as soon as the link is restored, the current state will be read by the lamp. (A useful note: if the lighting desk fails, then unplug the cables from the back to hold the present state, restart the lighting desk, set the state and then reconnect the cables. This will prevent a black out when the desk is reset.)		*DMX is a multiplexed system: unlike a serial system which may only send data when the lighting state changes (i.e. if a fixture misses a state change then it will hold the previous state until the next state change), DMX constantly sends the state up to thirty times a second. If the link from the desk to a fixture is broken, then the fixture will hold the last state, but as soon as the link is restored, the current state will be read by the lamp. (A useful note: if the lighting desk fails, then unplug the cables from the back to hold the present state, restart the lighting desk, set the state and then reconnect the cables. This will prevent a black out when the desk is reset.)