INTRODUCTION
In addition to being the easiest and quickest video mapping tool, MadMapper can also control lighting? How does that work?
We will explain the theory of operation to control lights, and more specifically LED strips, with MadMappers new MadLight feature. For that, we will first do an overview of the devices and technologies needed. Then we will see an example of a simple LED strip installation followed by some details of the installation of “The Cave”.
Note that this tutorial focuses on LED strips, but MadLight can control any DMX512 compatible device.
Try-this-at-home-with-care disclaimer
** Working with electrical devices requires some knowledge to avoid problems or even life threatening accidents. While you can realize this kind of installation without having to work with AC power, some power supplies require wiring by the end user. If you are unsure about how to do this, ask someone with the appropriate knowledge, preferably a certified electrician. **
** Low voltages used to power LEDs are not lethal but can be dangerous. Short circuits or undersized cables can cause a fire, so always check your connections and ask specialists if you are unsure. The author of this article and GarageCUBE assume no responsibility for misuse of this documentation. **
Technical description
Before explaining the tool chain needed to control LEDs from MadMapper, we need an introduction to the technologies and devices used. The following is a descriptive list:
LED STRIPS
These consist of a flexible ribbon of synthetic material (usually kapton) on which copper has been layered, exactly like an electronic printed circuit board (PCB). This allows for reels of pre-soldered LEDs where only two wires can supply power to hundreds of LEDs. The bottom side is usually equipped with tape to easily stick them anywhere. As they are flexible, they can adapt to a great variety of shapes.
While they were initially made for signage (they can easy be used as a backlight instead of a fluorescent tube because they have a longer lifespan and consume less power), they became cheap enough to be used in a variety of ways, from home decoration to artistic installations.
Led strips can be found in common LED colors (white, blue, etc..), or equipped with RGB LEDs to be able to reproduce different colors. They vary in LED density (common values are 30 or 60 LEDs per meter), voltage and power rating. They can usually be found in reels of 5 meters and cut in order to meet a desired length. In addition to individual LED, they are already equipped with current limitation resistors, so connecting them to a DC power supply is sufficient to light them with full power. Note that common LED strips have all their LEDs connected together (usually by groups of 3 LEDs), so to make segments controlled individually they need to be cut and wired separately.
attributes:
* rated voltage
* maximum current consumption
* fixed color or RGB (this affects the number of channels needed)
* number of individually controllable segments needed
POWER SUPPLY
LED strips work with DC voltage. They usually need 12 or 24 volts to be powered at full intensity. So we will need an AC-DC power supply connected to the grid to output DC voltage with sufficient current to light all the LED strips.
The power supply needs to have enough power to light all the LED strips. Check the specification of your LED strips to find the current consumption (often provided per meter). Then multiply by the total length of strips that you plan to use. If the result is higher than what the power supply can provide, you either need a bigger power supply or add another one. It is possible to use one power supply per LED dimmer. If you need a lot of channels but few currents per channel, you can share an power supply between multiple LED dimmers.
It is recommended to choose a quality power supply, ideally with temperature and short circuit protection. For big setups, a power supply with power factor correction (PFC) is a good choice to avoid polluting the mains and reduce conflicts with other equipment.
attributes:
* input voltage (110 or 220 volts if not auto-switch)
* output voltage (must match LED strip and LED dimmer specifications)
* maximum power or current (one can be deduced from the other)
LED DIMMER
To dim an LED strip, we cannot just vary the DC voltage to reduce the intensity of the LEDs. LEDs have a voltage threshold under which they just won’t turn on. So the common way to dim LEDs are to switch them on, then off, then on again very fast, in fact faster than the human eye can comprehend. So we won’t be able to see them flicker, and we will only notice the variation in intensity. Electrically, this is known as pulse-width modulation (PWM). There are a lot of different devices that can be found on the internet that take DMX input, DC voltage input and then provide numbers of power with PWM outputs to connect the LED strips.
Note that inherent to LED technology and PWM control, we won’t be able to produce very low intensities of light. LEDs don’t have a linear curve of intensity so when they are lit a little, they are already quite shiny. Some led dimmers compensate for this by having a non-linear PWM curve.
Like many DMX fixtures, LED dimmers have DMX address DIP switches. We will see later how to configure them, but just remember that they are used to configure the starting DMX address of the LED dimmer.
LED dimmers are usually not equipped with output fuses. While this is not a big problem, this gives you no security in case of short circuit. If this happens, output will probably be destroyed. You can find in-line fuses that you can add to your connections if you want more safety, but with high channel counts this can be time and cost prohibitive. But in all cases, always check your connection with an ohm-meter to prevent short circuits!
attributes:
* number of outputs
* maximum current for the whole device
* maximum current by output
DMX512 PROTOCOL
DMX512 is a simple bus protocol used in theaters and live shows to send light intensity information (or light position, color and so on) to the light fixtures that are set up on stage. We usually simply talk about DMX.
DMX is usually sent from lighting desks through cables that daisy chain from one fixture to the next. We won’t go too far in the DMX bus description (wikipedia does it better than we can), but for now you can figure it as an array of 512 values (often called channels) that are sent from the DMX emitter to the light fixtures, multiple times per second. All the fixtures receive the full array and need to be assigned a numerical address so they know which value to use. For example, if we have the case of a 4 output dimmer pack configured to address 10, it will used the value of the channel 10 of the DMX array for its first output, the value of the channel 11 for its second output and so on until channel 13. It won’t care about all the other channels. This allows us to assign the same channel to multiple fixtures. DMX protocols have a maximum number of 512 channels. In big shows or when using RGB led strips, this can quickly become a limitation. Luckily, MadMapper is able to manage multiple DMX outputs at the same time, so we are able to work around this limitation. Each DMX output will be called a “universe”.
The standard connector used for DMX is the 5-pin XLR, but as they are less common than the 3-pin XLR used for audio and as one-way DMX uses only 3 wires, the 3-pin XLR are often used. (We won’t talk here about two-way DMX called RDM, but they do exist.) The DMX uses female XLR for output and male XLR as input (the opposite of audio XLR usage).
attributes:
* number of universes needed (if more than one)
DMX512 INTERFACES
DMX512 interfaces allow to send or receive DMX512 from a computer. This is the bridge which allows MadMapper to output the light intensity information to the LED dimmers. MadMapper currently supports the following interfaces:
USB – DMX512 INTERFACE
Since the release of MadMapper 1.4, the DMXUSB Pro interfaces from Enttec are fully supported for DMX512 compliant devices. It has the big advantage to be very easy to setup and doesn’t require any external power supply, just a standard USB cable and a 5-pin XLR cable. The drawback is that you can connect only one USBDMX PRO and so it is limited to only one universe. For small setups or tests, this one will do the job flawlessly. But as soon as you need more than one DMX512 universe in your installation (512 channels), you will need to go with multiple Art-net DMX512 interfaces.
ART-NET INTERFACE
Art-Net is the modern evolution of the DMX512 protocol. It has the big advantage of being able to run on top of the ethernet protocol. It can be used to easily interface hardware to hardware or software to hardware by using common ethernet cables and switches (hubs). In our case, it will be used to send the channel/value information to an Art-Net -> DMX interface.
As stated before, LED dimmers use the DMX protocol to receive light intensity information. MadMapper is able to send light intensity information using the Art-net protocol, so we can use devices that can translate Art-net to DMX. This can seem tedious but it offers the big advantage of controlling a large number of light channels by having multiple Art-net to DMX interfaces (multiple universes, more than 512 channels).
For this installation, we use the Enttec Open DMX Ethernet (ODE) to show the most complex example. Note that ODE and DMXUSB PRO both require the use of 5-pin XLR connectors, so if you plan to use a 3-pin XLR you will need an adapter like this:
THEORY
All of this is a bit abstract, so here is a graph to summarize the theory of operation.
With USB:
With Art-net/Ethernet:
Light intensity will be determined by video fed to MadMapper, sent through Art-Net over ethernet or USB to a DMX interface, and then to the LED dimmer. The LED dimmer will take the intensity value depending on their allowed addresses and dim the LED strip connected to the corresponding output by fast-switching the voltage provided by the power supply. A little more clear now? No? Ok, let’s look at an example.
PHYSICAL EXAMPLE: PRESENTATION
Now we need something more tangible. What about an RGB LED strip of audio VU-meters?
Controlling LED strips from a video only to make a VU-meter can seem like overkill, but it is perfect for a simple example.
HARDWARE LIST
For this demonstration setup, we will need the following hardware:
* Enttec ODE
* ODE power supply
* ethernet cable
* 5 to 3 pin XLR adapter cable
* male XLR connector
* 12V power supply
* 24 channel LED dimmer
* 8 segments of an RGB LED strip
The LED strip used here is already stuck on a U shaped aluminum profile. This is convenient to make a little test and to move it around without damaging it. The lengths used here are short but if the LED dimmer and the power supply were powerful enough, 5 meter strips could be connected in the same way. Here is a closeup picture of the soldering pads at the end of the LED strip:
On the right we can see the pads on which the cable is soldered. They are tiny, so soldering is not always easy. Single color LED strips are more convenient because there are only two connections to make (positive and negative) and so there is more space between the soldering pads. Notice that after 3 LEDs there is another solder pad separated by a line. This is the cut mark defining where the strip can be cut. If needed, each part can be soldered again on wire and controlled independently.
Be careful to choose wires with enough copper section for the current drawn by your LED strip lit at full intensity. If the wire is too thin, there will be voltage drop across the line resulting in a loss of intensity. In extreme cases, the wire can even burn and start a fire. It is usually estimated that 1mm² wire is enough for 10 amps. Note that in the case of RGB LED strips, the line providing the voltage to the strip must be able to handle the sum of the current drawn by all three colors.
LED strips are usually common anode. This means that the positive side of the red green and blue LEDs are tied together and always connected to the supply voltage. There is one cathode by colors and they are switched individually by the LED dimmer to generate different intensities.
The LED dimmer used here is designed to be used with RGB LED strips so it provides output grouped by 3 channels on 4 way connectors. Single color LED strips could be connected with this dimmer. In this case, R is channel 1, G channel 2, B channel 3 and so on for following outputs.
All the dimmer inputs and outputs are provided on screwable plugs. This is very convenient for power and LED strips connections, but we also need to connect a male XLR plug to the DMX input.
Software setup
We need something to generate the video data from the audio to represent a VU-meter. We’ll use the MAD_Equalizer from the MadLab applications as it is perfectly suitable for our purposes.
This little piece of software takes an audio input (line in or computer internal microphone if available) and provides a parametric VU-meter that sends its resulting video image to Syphon. It generates an array of colored squares that will react to audio (frequencies on horizontal axis and volume on color and vertical axis). It will be used as an input by MadMapper and then animate the 8 segments of the RGB LED strips. Each LED strip will receive 3 different values of PWM and so it will reproduce the color of the corresponding VU-meter segment.
Configure it to display only one column (so covering the full audio spectrum) and divide the vertical scale into 8 segments.
In MadMapper, select the MAD_Equalizer Syphon stream in the medias tab.
On the left tab, we can see that MadMapper will output the intensity values on universe 0,0 starting at DMX channel 1. This will be the address of our LED dimmer. MadMapper conveniently displays how to configure DIP switches to assign the address to the LED dimmer.
The next fixture will start at address 4 because RGB values need 3 DMX channels to be sent. The DIP switches are now displayed for address 4 but we won’t need it because we only use one 24 channel LED dimmer. When configured to have the address 1, it will take the first channel value for the first output, address 2 for the second and so on. If we need to add a second LED dimmer, it will have address 25, and then we would need to update the DIP switches of this new dimmer accordingly.
Network configuration
As the Open Dmx Ethernet is directly connected to the ethernet port of the computer, there will be no DHCP. Manually configure the ethernet interface as following:
* IP address : 10.20.224.2
* netmask : 255.255.255.0
These settings work with an out of the box ODE. The computer and the ODE only need to be in the same network segment. There is no need to specify the ODE address on the computer. Refer to the Enttec documentation for more details about the ODE network configuration.
Also note that we don’t need to do anything about the DMX universe because without special configuration, a new ODE will be configured to use DMX universe 0,0.
Then activate the MadMapper Art-Net output. Go to the preferences panel in the DMX Output tab:
Choose Art-Net protocol and then select the ethernet interface.
Wiring
Use the ethernet cable to connect the ODE to the computer and plug the power supply into the power strip. Leave the power strip off for now.
Connect the 5-to-3 pin XLR cable to the ODE.
Connect the other end of the cable to the LED dimmer. As this LED dimmer provides all connections on screwable terminal, we will need to screw a male 3-pin XLR connector to the DMX input. Configure the LED dimmer to DMX address 1 by using the DIP switches. Remember that this information is shown in the left pane of MadMapper when you select a fixture.
Screw the power supply to the LED dimmer connector and then plug it into the power strip.
Connect the LED strips to the LED dimmer, starting with output 1.
TESTING
Everything is connected now. Toggle the switch of the power strip and play some music!
Wow, shiny!
The Cave
The Cave was presented during the 2012 edition of the Mapping festival and was the first application of this new possibility offered by sending DMX from MadMapper.
The concept was proposed by Iregular & Greg Barth, two artists who were invited to the Mapping Festival 2012 in Geneva, Switzerland. Their idea was adapted to fit with the new Art-net feature of MadMapper that took place in the Zoo nightclub.
The artists submitted a 3d model of a cave that was to be constructed as a big structure around the stage. It was all realized with beams of wood painted in black.
On the back of the stage there were 4 big triangles with fabric stretched upon them that were used as mapped screens. 100 meters of white LED strips were cut into 100 segments of about 1 meter and stuck on all the visible edges of the mesh to outline the geometric shapes of the structure.
The segments were added as fixtures in the MadMapper project in a way so they reflected their physical position as seen from the dance floor. It was then possible to play clips in MadMapper and control them as a “scattered screen”.
http://www.madmapper.com/controlling-led-strips-from-madmapper/
