DMX Frequently Asked Questions

A. DMX is an international standard digital lighting control protocol.

A. DMX Stands for “Digital Multiplex”.

A. It is called DMX 512 as there are 512 channels on a DMX controller. 512 DMX channels is known as one DMX Universe.

A. Yes, it is possible to have multiple DMX universes when more channels are required but each universe consists of 1 to 512 channels.

A. A DMX channel or DMX has 255 individual steps from 1 – 256.

A. A single colour LED lamp will take up one DMX channel or DMX address and by increasing or decreasing the value of that address in steps (between 1 - 255) the lamp will increase or decrease in brightness, the higher the number the brighter the lamp will be.

A. Some products take up more DMX channels, for example an RGB colour changing LED lamp will take up three DMX addresses (one for each colour). By increasing or decreasing the DMX values of each of the three channels will increase or decrease the intensity of each of the colours allowing you to mix more colours.

A. A DMX decoder decodes the DMX signal from the controller and converts it into a process. For example, when controlling an LED lamp, it decodes the single from DMX to the LED dimming protocol which is PWM.

A. You can control most electrical products with DMX, for example you can control a stepper motor accurately by assigning a DMX channel value to the number of pulses sent to the motor you can position it accurately.

A. A typical DMX system will have a controller, that can be a DMX wall panel or DMX desk or even a DMX computer program on a PC or laptop. This is connected to a DMX decoder or a product with a built in DMX decoder through a screened DMX cable. The decoder decodes the DMX digital signal sent from the controller to perform a task.

A. Yes you can, the lighting device is connected to a DMX decoder which is connected to the controller via a DMX signal cable. The DMX decoder is then set to a DMX address so that it is the only device on the DMX network that will respond to the signal for that address.

A. Usually there is a digital display and menu buttons on the DMX decoder, you can set the address from 001 up to 512.

A. First you will need to know how many DMX channels your device uses. For example, an RGBW LED lamp will take up four addresses (one for each colour). If you wanted to control one RGBW lamp separately to another RGBW lamp you would need to set them to different addresses. The first RGBW lamp decoder would be set to address number 001, that then takes up four addresses in DMX so the next available address would be 005. So set the next RGBW decoder to address 005. If you wanted to control both lamps together then you would set both decoders to the same address.

A. Most DMX decoders have a digital display and menu buttons but some small decoders don’t have the space so they use “Dip” switches to set the address.

A. Each dip switch has a value in the following format. Switch 1 = 1, 2 = 2, 3 = 4, 4 = 8, 5 = 16, 6 = 32, 7 = 64, 8 = 128 & 9 = 256. By adding these values together, you can set the address to anything between 001 & 512. For example, to set the DMX address to 028 you would set dip switches 5, 4 & 3 to the “on” position. The value of these switches adds up to 28 (16 + 8 + 4 = 28). As long as the switch values add up to the DMX address you can do different combinations.

A. The DMX signal travels along a DMX cable and is picked up by all the decoders connected to it, only the decoder that is set to the address that is being sent down the cable responds to the DMX signal.

A. It is recommended that you use a screened cable for the DMX signal as it is a very low voltage. If this cable is a long cable, you can get interference from other cables such as amins power cables that run alongside the DMX cable. By using a screened cable will eliminate these interference signals.

A. No the DALI system uses a completely different protocol.

A. There are wireless DMX systems available, they consist of a DMX transmitter which you connect to your DMX controller and a DMX receiver which you connect to your DMX decoders.

A. DMX decoders have “DMX in” and a “DMX out” connectors, simply connect each one together in a daisy chain. So, from the DMX controller to the first decoder DMX input terminal, then out of the output terminals to the next DMX input terminal and so on.

A. The most popular DMX connections are a three pin or five pin XLR connector. The five pin XLR connector is seen to be more professional and so is found on professional lighting desks usually in theatres or TV studios. RJ45 connectors are also used for short DMX cable runs and most professional DMX decoders have “hard wired” connections.

A. The DMX signal will bounce back along the DMX line like a ball so it is recommended that a special DMX terminator plug is fitted to the last DMX decoders output terminals on the last decoder in the line.

A. A DMX terminator plug is a plug that should be placed into the DMX output socket on the last DMX decoder in a chain, it contains a 120 Ohm resistor to put a load on the output and stop bounce back signals from interfering with the DMX signal.

A. You can fit a 120 Ohm resistor between the DMX + & - output terminals.

A. It is recommended to run a DMX cable no more than 100m and no more than 32 devices.

A. There are DMX booster products available that will boost the DMX signal enabling you to run much longer DMX cables.

A. When using a DMX signal booster, you can increase the number of DMX devices on the system.

A. A DMX controller transmits a packet of DMX information which is 8 BITS long and contains 255 steps. When 16 Bit is used it transmits two packets of information a total of 510 steps which enables smoother dimming. For standard dimming 8 BIT is fine but if you require a much smoother adjustment then 16 BIT would be more suitable.

A. RDM stands for “Remote Device Management”

A. RDM allows two-way communication between the RDM enabled lighting controller and the RDM enabled DMX decoder. It allows you to change the menu settings on an RDM enabled DMX decoder and also it will allow the RDM enabled fixture to report back to the desk certain information such as lamp life etc.

A. You can download a DMX program onto your computer or laptop which will enable you to control your DMX lighting very easily. You will need to purchase a USB to XLR converter which are sometimes supplied with the program.

A. Yes DMX Wall panels are readily available although they tend to have fixed DMX channels so you are limited to the number of zones and channels that are available on the wall panel. For example, a single zone wall panel will control one set of MDX addresses. If you have an RGBW wall panel, you have to set your DMX address to 001 and any other decoders on that circuit would be set to 001 so they all do the same thing. If you have a four zone DMX wall panel then all the decoders on zone one would be set to address 001, this will take up four addresses, one for each colour so the next available address would be 005 for zone 2, 009 for zone 3 and 012 for zone 4.

A. Yes, for example a moving head or moving mirror luminaire or multi-colour laser show system can take up many addresses as they have many functions and will require a DMX address for each function. Some complex devices could even take up all 512 channels or one DMX universe.

A. Programming a DMX desk can take some time as you have to enter each step of the program into the memory of the desk. Programming DMX on a computer is easier as you can have a visual representation of your lighting rig on the screen and select each device using a mouse pointer, you can then select the colour and position it as required. Programming a DMX desk would take longer as you would have to elect each step of the program and enter it into the desk memory.

A. Simply select the program that you have written and press play. The program speed can usually be adjusted on the fly as the program is running.

A. Yes you can, most DMX desks have a built-in microphone which can be used to pick up the sound in the room. Most desks will also have an audio input jack socket to feed the sound directly into the desk. There is a music sensitivity control on the desk so that once in sound to light mode you can adjust this control so that the lighting that the desk is controlling can be set to follow the base beat of the music or other effects.

A. 0-10v is an old analogue system that used to be used in theatres to control the lighting. It required a control cable for each light in the lighting rig, it was a very clunky system. As DMX is digital it only requires one cable to go around all the lights on the lighting rig so there is much less wiring involved. It is also a more reliable system and controls the lighting and other products a lot more accurately and it can be programmed to run various sequencies. DMX can also run many other devices not just lighting.

A. There are DMX recorders that can store a program onto a memory card and played over and over again.

A. Some lighting devices have built in DMX decoders so there is no need to have a separate DMX decoder. These can be addressed the same as a if using a separate DMX decoder.

A. Some of the smaller desks are limited to the number of DMX channels they can use however some have upper and lower levels on each slider so for example if a desk has 8 x DMX slider controls it may can have a button that turns the 1 to 8 sliders into DMX addresses 9-16 etc.

A. Yes, it is possible, by downloading a DMX program onto your iPad Smart phone or laptop and connecting to a wireless DMX transmitter the signal can be transmitted to a DMX receiver that is then plugged into your lighting rig.

A. No, there are many home and office automation systems that use DMX as a standard protocol.

A. This is a very controversial question, with wireless systems there is always a chance that signals can be interfered with whereas with a wired system this would not happen. Most concerts and TV productions use wireless DMX however so the system is improving all the time and providing you don’t purchase a cheap wireless system you should have no problems. Wireless systems are of course easier to set up and require far less wiring.

A. A DMX desk is harder to program and takes more time, a computer program is a lot easier to use and operate however if you only have a few lights on your rig, then a desk should be simple to use. Computer controlled DMX systems tend to be used in larger DMX installations.

A. A lot of band lighting is automated so just plug and play but if you want more control over your lighting such as softer, slow colour changing lights for the slower music then you may want to invest in a small DMX system which will enable you to have more control over your lights.

A. This is possible however you should connect the two controllers to a DMX Merger that will merge the two controllers into one DMX output.

A. LED lights are dimmed and controlled using a system called PWM (pulse width modulation). This is a system that varies the length of the pulses that switch the LED’s on and off. Flickering and banding occurs when the shutter speed of your camera matches the PWM frequency of the controller. This effect is similar to on a film with the wheels on a car going round and appearing to go backwards or appearing to be stationary. To stop this effect with your lights you need a DMX decoder with a high PWM frequency. This is usually a professional grade DMX decoder with a high PWM frequency. Some DMX decoders have a very high PWM frequency of 30 – 35KHz.

A. Most DMX decoders will allow you to change the dimming curve of your lights from Linear to Logarithmic. If some of you r lights are set to Linear, they will dim evenly from off to full, if some are set to Logarithmic, they will dim slowly to start with then suddenly get brighter. Make sure your dimming curve settings are set the same.

A. Yes, just set the DMX address to the same on the lights that you want to group.

A. A microphone cable is a screened cable and is fitted with male and female three pin XLR connectors at both ends which is the same type of connector used on many DMX decoders and desks so many people are tempted to use these, however it should be a last resort as a true DMX cable has a higher impedance capability and can handle 110 – 120 Ohms while a standard microphone cable can only handle 75 Ohms. It will transmit the DMX signal but not very well and you may have flickering issues or find it may not control your lighting as well as it should. A DMX cable receive Digital signals better than analogue signals and XLR cables receive analogue signal better than DMX signals.

A. You can purchase a Three Pin to Five Pin XLR male or female converter which will do the job or you can cut off the three pin XLR connectors off the cable and solder five pin XLR connectors onto it.

A. Pin 1 is the ground (screened) wire, Pin 2 is the data – wire and pin 3 is the data + wire.

A. Pin 1 is the ground (screened) wire, Pin 2 is the data – wire and pin 3 is the data + wire, pins four and five are not currently used.

A. The DMX voltage is very low at maximum of 6v DC with a 250mA maximum current.

A. Master Mode means that you can control basic functions and some programs directly from the DMX decoder. If your DMX decoder has a digital display these features can be selected easily using the menu buttons. If your decoder has dip switches there is usually an additional switch “10” which will put the unit into Master Mode then by varying the other dip switches you can select and have basic dimming to pre-set levels and basic programs to select.

A. A Standard DMX decoder is a device that requires a DMX signal to operate it. Some DMX decoders however have a “Master Mode” which enables some basic functions and programs to be run. Typically, you can select individual channels and increase or decrease the brightness of the light that is connected to it. This will effectively enable you to mix any colour by varying the brightness of each channel. Usually, Master Mode also has some basic programs built in such as fading or chasing through the channels. These programs can usually be adjusted for run speed.

A. DMX originated as a Theatre Lighting control system. Replacing the old 0-10v system.

A. DMX was developed in 1986.

A. A DMX BUS is simply another name for the DMX signal cable.

A. No most standard DMX decoders are 8 BITS. Professional DMX decoders would also have 16 BIT built in. You can set these decoders to 8 BIT or 16 BIT as required.

A. DMX decoders can have any number of channels but the more channels there are the larger the Decoder. Single channel Decoders are available for controlling the brightness of one light but then a large theatre lighting product may have hundreds of channels to control all its many features.

A. Many DMX decoders have the ability to change the number of channels that they have so for example a five channel DMX decoder may be set to work in single channel mode so that all five outputs do the same thing ad it will take up one DMX address.

A. A DMX Personality is what a DMX channel or group of channels control on a lighting fixture. It gives the start address and what each slider on the desk will do. It comes in the form of a fil e of information that can be entered into the lighting desk.

A. A DMX Scene can be a pre-set lighting level or for moving head lighting fixtures it can be a pre-set position which the lights go to when the scene button is pressed.

A. A chase is a number of pre-set scenes that can be entered into a DMX program on the desk which will then play each of the scenes in a sequence.

A. That depends on what lights you are controlling, if it is a single light and you just want to dim it up and down then you will need just one channel of DMX but if you have a colour changing light which has Red, Green, Blue and White colours then you will need four channels, one for each colour.

A. The DMX start address is the first available address on your controller that is free. For example, if you have a device that is taking up 15 x DMX addresses, the next fixtures starting address would be 16 as that is the next available address that is not being used.

A. You will only be able to control certain features on your DMX light not all of them, you will be able to control only the first eight channels so whatever those eight channels do will be the only features you can control.

A. DMX Splitters enables you to run longer lengths of DMX cables and control more devices as they boost the DMX signal whilst splitting one DMX cable into multiple cables which can be run to more devices.

A. Yes you can but you must ensure that the DMX splitter is RDM compatible and will accept bi-directional DMX signals.

A. No, you can have your devices in any order on the DMX circuit.

A. You can add additional DMX devices at any point in the DMX universe as long as you do not exceed the total recommended number of devices. Simply place your device where it is needed, unplug the DMX cable from the nearest device and connect it to the input of your new device then run a DMX cable from the new device back into the input of the device you have disconnected to restore the chain. You will then need to address your new device to the next available DMX start address.

A. Make sure that you have a terminator plug fitted to the output on the last DMX device. If one is not fitted you can get a DMX Signal bounce back which can cause this effect.

A. Most DMX decoders or DMX fixtures have a small LED indicator which flickers when a DMX signal is detected. Some have a dot on the display that indicates the presence of a DMX signal. If your fixture does not include this feature, you can purchase an XLR plug that you can plug into your DMX circuit, at any point, the XLR plug has an LED on the top that indicates the presence of a DMX signal.

A. Yes you can but they will both do the same thing as they will respond to the DMX signal that is sent to that DMX address.

A. Yes DMX can control many things not only lighting, the manual will tell you how many channels the smoke machine takes and what each channel does. All you have to do is to set the DMX address on the smoke machine to the first available start address.

A. This is a common question, both protocols have their own advantages. DMX is used mostly in the theatre, TV and stage productions such as concerts etc. DALI is used mainly in large building projects such as hospitals. The biggest advantage with DALI is the bi-directional communications which tells the DALI Master if there are any products that are not working correctly etc. You can also set up set scenes to work with room sensors that will turn on the lights when people enter a room. DMX is easier to understand and you can connect more devices on the DMX system. DMX is probably easier and less complicated for smaller domestic or office installs.

A. That depends on the type of home automation system you are using; some companies use the DMX protocol in conjunction with their home automation products. Ask your installer what protocols their system use.

A. Yes DMX is much better and it is a digital protocol rather than an analogue protocol.

A. Yes, DMX is an international protocol so any DMX product will work with other DMX products.

A. You may get something called DMX bounce which is when the DMX signal bounces back down the signal cable, this can cause flickering on your lights or it may cause the system not to work properly.

A. No, all DMX systems should have a DMX terminator on the output of the last product in the chain.

A. No you can’t, the voltage on the signal cable is very low with only milli-amps of current.

A. The screen on a DMX cable is earthed to stop any strong electrical currents from interfering with the DMX signal if a DMX signal lead is run alongside a power cable for example.

A. Most DMX decoders or devices with a built in DMX decoder have an LED either as part of the display or on the unit near the DMX menu buttons which lights up to indicate the presence of a DMX signal.

A. You have probably set all the DMX decoders to the same address, each light that you want to control separately needs to have its own address.

A. Some lighting manufacturers reversed the polarity of the DMX cables on the DMX input sockets, if the switch enables you to quickly switch the polarity of your DMX output.

A. No, you can only control one or the other. I would suggest that you re-wire the DMX output plug on the cable that is going to the lights that are wired the wrong way round as Pin 3 should be +.

A. Your RGBW tape will normally have a black wire which is common +, a red, green, blue and white wire. Connect the common + wire to the + output on the decoder then Red to channel 1, green to channel 2, blue to channel 3 and white to channel 4.

A. Yes you can, you will need to replace your existing RGBW remote control receiver with a DMX decoder. You can still use your existing LED Driver (power supply) which you would connect to your DMX decoder instead of your receiver. All you need then is to set the DMX address on the decoder to match the DMX output on your wall panel and connect the DMX signal cable to your decoder.

A. Some DMX decoders can be set to single channel, Dual channel, three channel, four channel or more modes. If your decoder has this then just set the mode you need and wire up the LED tape as detailed in the instructions. If it doesn’t have that facility then just use the first three channels 1, 2 & 3. You don’t need to connect anything to channel 4 & 5.

A. No, if you are only using the first six channels of the 12-channel decoder, the next available address to set the second decoder to would be address 7. You just need to bear in mind that if you ever connected anything to the other six channels on the first decoder, they would also work with the lighting that is connected to the second decoder, so you may want to re-address your second decoder to address 13 in that case as that would then be the next available address because in that situation you would then be using all 12 addresses on the first decoder.

A. It could be a number of things, but first check that you have addressed the fitting correctly. If they are then it could mean that there is a faulty cable from the last fitting that works to the rest of the lights in the chain. Replace the DMX lead from the last fitting that works, if the rest of the lights work then the fault is with the cable. If not then disconnect the first light that is not working, remove it from the chain and connect the DMX cable to the next light in the chain. If that cures the fault there is a problem with the unit that you have removed.

A. It looks like you may have connected the green cable on your LED tape to channel 1 and the red cable on your tape to channel 2 so when you select red the green lights up. Check your wiring from the tape to the DMX decoder. It should be red to CH 1, green to CH 2, Blue to CH 3 and white to Ch 4.

A. DMX Macros are a series of pre-programmed “effects” that are either built into the DMX fixture or the DMX controller. On a controller there is usually one fader that will run the macro programs built into the fixture. Depending on the value that the fader is set to would depend on the macro selected.

A. In your user manual you will have a DMX mode that the fixture can be set to which has values on one of the channels for running various programs if it has macros.

A. Your DMX desk will have a fader control that lists multiple functions for different DMX values on the fade. For example, DMX value: 000 – 025 creates a slow fade through the colours, so if the fader is set to that value the fixture will fade through the colours.

A. This depends on the complexity of the moving head unit. A basic moving head luminaire will have one channel for lamp brightness, one channel for pan, one channel for tilt, one channel for colour wheel and one channel for gobo selection so a minimum of five channels. A more complex luminaire will have many more channels so your 512 channels of DMX on one universe can be used very quickly just on one projector.

A. Moving head or moving mirror luminaires use stepper motors to accurately position the head or mirror. Stepper motors move in small increments or steps, the number of steps that the motor makes are determined by the DMX value on the controller. For example, the higher the DMX value the more pulses go to the motor so the further it turns.

A. A DMX Switch box is a box with a switch that enables you to connect two DMX controllers to the same DMX system but only one at a time. You can switch from one controller to the other in case one system fails.