Customer Question: Should I use a centralized or de-centralized controller for an element?

HolidayCoro sales/support often sees common, open-ended questions from our customers and here on our blog we post detailed responses publicly so that other people will be able to learn from the decision making process we use to answer these questions.

Today's question is:  "I am making 16 pyramids and would like to light them up using 3 or 4 Basic Rectangle RGB LED Waterproof Module per pyramid.  The pyramids will be in the front yard each about a yard apart.  My Question - should I buy 16x Item #30 Basic 3 Channel RGB DMX Controller or should I buy 2x Item #24 Basic RGB 27 Channel DMX Controller.  Is there any advantage to either in this situation?"

For this given project it has already been determined that basic or dumb RGB lights should be used as opposed to pixels and this is often the case when an element doesn't need the control that pixels offer or when there are larger distances between elements.  So the question becomes - should the basic RGB DMX controller be centralized in the form of a 27 channel (9 RGB outputs) DMX controller or individual 3 channel (1 RGB output) DMX controller in each element?  The issue comes down mainly to two factors - cost and complexity:

• Cost - The number of RGB lights won't change between the two methods, so we'll exclude that from the calculations, though what does mainly matter are wiring, power supplies, controllers.  Also, we need to determine he power consumption of the RGB Modules, which in this case consume about 100ma (1/10th of an amp) at 12v DC - or 16 elements x 4 modules is 6.4 amps total.  So, we'll take the number of individual elements here - 16 and do some comparison math with the two options: 
• Centralized - This method allows us to have one (or two in this case) centralized controllers - the costs involved are:
• $114 ($57 x 2) - 27 Channel DMX controllers
• $26 ($13 x 2) - 45w (3.75amps at 12v) power supply.  This solution would power each 27 channel controller with a single power supply.  It's a little tight on the power at 3.2 amps total per controller (32 modules per controller) but it should work.
• $20 ($10 x 2) - Waterproof housing.  The 27 channel controller isn't waterproof, so you'll need a waterproof/resistant housing and this varies by region, water/snow conditions and budget.
• $20 (100ft @ $.10 per foot x 2) - CAT5 wiring.  You'll need to get the output of the controller out to the individual elements and CAT5 would be a good solution here as the current consumption of the lights is below the current carying ability of CAT5 at a bout 3 to 4 amps and it has 8 wires, so you could double up each wire for the 4 wires required for RGB lights.
• ~$180 - Total
• De-Centralized - This method allows us to have an individual, 3 channel DMX controllers in each element - the costs involved are:
• $144 ($9 x 16) - 3 Channel, CAT5 based controllers
• $26 ($13 x 2) - 45w (3.75amps at 12v) power supply.
• $8 (80ft @ $.10 per foot) - CAT5 wiring.  Using the DMX+Power over CAT5 system, it is possible to inject power at the start of the string and again at the 8th element.
• $23 ($1.50 x 16) - 3 Way Splitters for the DMX signal+power.
• ~$201 - Total

Of course there are other minor costs - shrink wrap, solder, tools, shipping, etc and we've not included those in the calculations above.  So, on the surface, they look pretty much about the same from a cost basis, so let's take a closer look and consider all the other factors:

• Complexity
• Interconnections - Left out from above on both are how you'll interconnect the wiring from the element to the controllers.  
• Centralized - With the centralized solution, you could solder the CAT5 wire directly to the lights in the element and then have elements with 20, 15, 10 and 5 ft lengths of cable coming off them and then you'd fish that wire into the controller case and screw it down to the terminals on the controller.  The problems with this solution are that it makes future adjustments in length complicated since you've already set the length of the cable from the element to the controller when you built the element.  Additionally, you'll have to deal with elements that have attached wire and then manually wire up each element to the controller, adding to your display setup time.  An additional down side to this method is that you also have more wire spread out over your display which can present safety/tripping hazards.  The upside to this method is that it doesn't really require any additional connectors - just tin the wires where they go into the controller screw terminals.
• De-Centralized - If you've placed the individual CAT5 controllers in each element, that means that you can simply attach a 3 way splitter to each CAT5 plug, then plug in the necessary CAT5 cable between each element (5ft lengths in this case) in a daisy chain arrangement.  Then you just build a power injector for each of the two bands of 8 elements and this allows you to run the power and the DMX signal from one element to the next.  The amount of wire is limited as it only goes from one element to the next.  The down side is that you need to ensure that you control water ingress in to the CAT5 connectors and use a corrosion control spray - usually mounting the controller up-side down under the element would be more than sufficient to manage water ingress.  The real beauty of the Power+DMX over CAT system is that you can assembly your display quickly just by plugging into each element to the element next to it.

Factors to Consider When Designing an RGB Pixel Matrix

Over the years we at HolidayCoro have been asked why we only sell a single pixel matrix product - our 18" x 24" pixel with either 150 or 162 pixels.  Well, actually, we've produced a fair number of custom matrix based panel items for customers over the years and the main reason we don't offer all these variations for sale is because each project is so different.  The article hopes to provide information on factors that we consider when working with customers on designing a pixel matrix and hopefully this will help those building their own or working with us to custom produce one.

• What exactly is the purpose of the pixel matrix?
• Is this matrix intended to be dense enough that viewers will be able to see objects scrolling or displayed on it such as text, icons or logos?  
• What is the viewing distance from the matrix to the viewer?  If you've ever looked at a big screen TV up close, you can understand the relationship the size of the pixels (lights) have to the distance they are being viewed from.
• What is the viewing angle?  A curve pixel panel (such as a pixel megatree) can look odd if all the pixels in the matrix are not visible to the viewer.
• What is the shape of the matrix?  Is the matrix a cone, in the case of a pixel megatree, where the pixels at the top are in a much higher density than those at the bottom of the tree?  Is the matrix cylindrical?  flat? concave or convex?  All these designs have an effect on the final output, pixel density and mounting methods.
• Technical factors to consider include:
• Number of pixels - This is an important factor to consider and the number shouldn't be random - it should be based on the design requirements.  Look closely at how many pixels you'll need and their spacing from each other.  If needed, build a sample mock-up and view it from the distance and angle you expect your viewer to view it from. 
• Pixel height and width - Also consider how many pixels you may need to display certain items such as a text font which often require a 5x8 pattern.  Again, keep in mind that you will also need to have the pixels close enough that the human eye can make out the pattern - just because it might look good in the sequencing software doesn't mean that will translate into the real world.  
• Multi-Panel Alignment - If the matrix will be comprised of several panels, be sure to carefully consider the spacing within a panel and how it relates to the spacing induced between two adjoining panels.  This may mean that you will need to increase the center-to-center spacing of the lights to match that of the panel-to-panel gap.
• Mounting or support - An important part of any matrix is how you will mount it - because a matrix tends to be a flat area (excluding pixel megatrees), you'll need to think hard about what system you'll use to mount the substrate on to which the pixels are mounted. If that surface catches the air, there could be problems with it blowing over or toppling the support structure.  Also consider that you'll need to store this mounting system in the off-season - so if the panels need to go into an attic, consider the opening going to the attic.
• Substrate mounting - In most cases, you'll need to mount your pixels to a substrate - not only to support them but to maintain a clean and even spacing - there isn't anything worse than a matrix that has mis-aligned pixels.  How you mount those pixels can vary - it could be holes in coro like we do at HolidayCoro or it could be screwed or glued to wood slats or plywood - this all depends on your pixel type.
• Pixel type - The type of pixel you select will often be a by-product of the distance and viewing angle of the people viewing your matrix.  These pixels could be in a strip form, node form or module form and each has it's pros and cons and there is no one pixel that is best suited for all matrix types.
• Channels - Keep in mind that you'll often have many, many DMX channels on a matrix display and it makes sense to select pixel counts that fall within a set number of DMX universes - so don't design a pixel display that requires 180 pixels (18 wide by 10 high) if it could have been done in 163 pixels (18 wide by 9 high) which fits neatly into a single DMX universe and thus saves you a controller or controller output and also makes your sequencing easier to setup and manage.
• Repairs - Factor in that pixels DO fail and that you'll need to fix them.  So consider how easy it will be to remove and replace pixels.
• Cost / Budget - A matrix can grow in cost quite quickly when you factor in hundreds to thousands of pixels, so be sure to ask yourself the overall value of the matrix and how well it accomplishes its goal.  If this is just for announcing the radio station and song titles, a simple matrix will do - if you need to scroll logos or animations, you'll need a larger and more expensive matrix.
• Big isn't always better - Since pixels have come down in price and complexity, we've seen a number of pixel matrix panels (and pixel megatrees) in displays that just completely over-shadow and "hog" the display.  We believe that a well balanced display should be the ideal and that one mega-element can leave your audience so fixated on one area that they fail to see other areas and animation. 
• Software & Sequencing - Building a matrix panel is only one part of the process and the other major part is generating the sequencing for that panel.  Since it is nearly impossible to "hand" sequence matrix displays, you'll want to consider applications like LightShow Pro's matrix animator or Light-o-Rama's Superstar lights or other freeware applications that have been coming into the market.  You may even want to design your pixel display hardware, then start sequencing it before you buy or build it to evaluate how complex it will be to sequence the matrix. 

Customer Question: How many lights can be hooked up to the TinyPix?

HolidayCoro sales/support often sees common, open-ended questions from our customers and here on our blog we post detailed responses publicly so that other people will be able to learn from the decision making process we use to answer these questions.

Today's question is:  "I see that the smart pixels 8mm come in a max of 100 per string, however a TinyPix can control up to 170 pix. So if I wanted to control 150 8mm smart pixels, can I do that with one TinyPix? If so, how would the 2 strings (100 & 50) be hooked up to the TinyPix, and what kind of power supply would be required? (I assume the 45w one would be too small for 150 8mm Smart Pxels)."

I can see that the customer understands that the TinyPix controller can handle 170 pixels (510 DMX channels (170 * 3) or almost a full DMX universe that is 512 DMX channels) as that is covered in our documentation on the product page.  I can also see that the customer is aware from the product page for the 8mm smart pixel nodes that the pixels come shipped in 100 count maximum per string.  So, we have several issues here, some of which we have information on and some we don't.

Design - There isn't any design information provided, so we don't know if these are being used in a concentrated matrix or string over a long distance, such as a pixel tree or a soffit on a house.  Why this matters is because if the pixel nodes are all close together, it can be fairly easy to inject power (more on that in a minute) as where if they are in a long single string over a distance, it can be harder/more complex to inject power.  Additionally, we don't know if this is for a single element or many elements and the distances of those elements.  We would be generally suspicious if the TinyPix is even the correct item for this design because we suspect that it would be one of several units where a centralized pixel controller would be a better match.

Signal - A TinyPix controller is a RS-485 based controller and thus needs a DMX source, such as our Actidongle.  A single Actidongle could output 512 channels, so it could handle the 150 pixels (450 DMX channels) without issue - IF - the customer only has one of these items with such a high channel count.  If the customer has several other 150 pixel elements, they would need more DMX dongles and at some point it is likely cheaper to invest into a centralized pixel controller with a E1.31 inface.  Again, since we don't know anything about the overall design the customer has in mind, we can't recommend a specific solution here or if the TinyPix is even the right item for this customer.

Power - An important part of any RGB design is power management - we've covered this in many articles and knowledge base articles.  So, given that we know we are going to have problems if we try hooking more than 150 pixels together end-to-end from a power loss standpoint, we recommend the customer review our blog post about how to manage power injection and power supply selection (because the customer had also asked if the 45w power supply was sufficient to power them.)

So, to recap - yes, the pixels can be connected end-to-end in an amount UP TO 170 but just because that can technically be done by soldering the wires together to make a single length, doesn't mean they will work without managing the power issues.  The issue at hand is that there will be just too much power drop over the pixel wiring and thus power injection would need to take place, likely at the start (through the controller power outputs) and again at the end of the string.  This is what we recommend with our 163 and 150 pixel scrolling RGB matrix signs since it is easy to put power in at both ends of the wire, thus resolving the power drop issues since everything is close together.  If the pixels were used on, say, the front of a house or to outline windows, you'd need to still carry the power to the end or middle of the string for power injection.

The second part of the customer's question if our 45 watt power supply will be able to power all 150 nodes.  So, first we need to look at the overall power consumption of the nodes, which is:  White (all three colors) 100 Nodes: 3.6 amps / ~44 Watts  We can see right away that at 44 Watts for 100, that a 45 Watt power supply isn't going to cut it since 44 (100 nodes) + 22 (50 nodes) would be 66 Watts total, plus add in another few Watts for line losses and a safety factor and we are up towards about 75-80 Watts to be safe.  This excludes looking at any other factors such as additional controllers, etc - hence, why it is good to know the overall design involved.  So, normally I would just recommend hooking up a 250 to 350 Watt power supply.  They are not that expensive and likely the customer also has other controllers that could also piggy-back off this same power supply.

So, in conclusion - the customer would best benefit by providing as much detail as possible about the overall scope of the project and where this specific element fits into that project.  We understand that often customer just want a simple answer to their question and do not yet understand the underlying complexities that comprise an important part of the decision making process.  In this case, it would be helpful if the customer were to review and then understand the power and DMX addressing issues under-lying the technology in the TinyPix (and all DMX controllers.)  While this process can be long and tedious - taking weeks or months for some customers, this knowledge is a fundamental requirement for customers selecting a completely DIY solution, as we talked about in our DIY vs Commercial solutions blog post.

How many lights can be connected to a controller, what controller do I need for RGB lights, what wiring should I use for RGB lights and/or what power supply do I need for my RGB lights?

We often get requests from customers that ask how many lights they can connect to a controller, how many lights can be connected to a controller/power supply, what type of wire they need to hook up their lights and/or controllers or what power supply they should choose - and this blog post will work to answer those questions. This article assumes you are working with RGB lights and using a DMX based, constant voltage (all HolidayCoro controllers are constant voltage) controller, though the concepts will often apply to other controller types.  If the following information looks too complicated to learn or you'd rather just "have the answer", I'd recommend against working with a DIY lighting solution because a failure to fully understand the power requirements in some parts of the system can result in damage to the hardware all the way to house fires - and I've seen them both occur - so DO NOT "wing it" here.  Alternately, you can pay someone to "run the numbers" or there are vendors that sell plug-n-play systems and while they are not as flexible as a completely DIY system, there will be little to no need to understand power requirements - just plug-n-play.

The key to understanding how many lights can be connected to a given controller, it is important to see the lights and controller as only individual parts in a system that consists of:

Lights < Lighting Wiring < Controller < Power Wiring < Power Supply

Let's work through the chain and examine each part, starting with:

• Lights
• Purpose:  The lights are the final end-goal of any lighting system and they provide the light output for your display.
• Selection:  Lights are selected on a wide variety of factors - more than can be fully described in this post but some of the factors are:
• Physical:  You'll want to select the physical format, be that modules (square, rectangle, etc), nodes (8mm/12mm usually) or strip that best suits the mounting method and directional change (going around corners, curves, etc) requirements.
• Voltage:  LED lights can come in a variety of voltages, usually 5V and 12V DC.  There are advantages and disadvantages of both of these common voltage ranges so refer to additional sources on proper voltage selection.  In general, you can go longer distances with higher voltage drops with higher voltage lights (12v) than low voltage drops (5v), though low voltage (5v) is much more power efficient and sometimes has brighter output.
• Optics:  This can include output angle (60, 90, 180, 360 degrees, etc), color mixing (5050 on-die LED, Tri-Color 8mm, three 5mm separate LEDs, etc), light diffusion and many other factors.
• Control type:  LED's can be controlled via constant current or constant voltage.  Constant current controllers are usually designed into dedicated systems like floods and it requires a specifically matched LED or LEDs to a specific controller as where constant voltage controller allows any number of LED lights as along as they are below the output requirements of the controller.  For pixel lights - the pixel is always supplied with constant voltage, even if in the chip it is constant current, so for pixels, consider them constant voltage devices.
• Lighting Wiring
• Purpose:  This wiring is either the wiring between each LED light in a string, such as in the case of RGB LED nodes or it maybe a circuit board in the case of RGB strip lights.  This wiring brings the power from the controller down to each light.
• Selection:  There are no "standards" or "normal" wiring types here - each vendors wiring can be different.  One vendor may sell RGB nodes with 24 AWG wire (thin) compared to another vendor that uses 18 AWG (thicker) wire and they can look exactly the same.  I would not always trust the data provided by the vendor, more so if your supplier is outside the US as they often lie or copy other vendor specs even if they don't match the actual product.  In an ideal world, you would want the thickest gauge wire possible as it will be able to best transport the power with the least losses but the reality is that thicker wire is harder to work with (less flexible, harder to solder to circuit boards or lights) and is more expensive, so usually there is some "balance" between cost, weight and the distance needed for the lights to be run over.
• Additional information:  Ideally, your vendor will list the maximum run on serially/continuously connected lights that can be supported before there is a "reasonable" drop in power.  So, for example, you might have one vendor that sells a 100 count string of 12v RGB nodes and they have a voltage drop from the start to the end of the string of 6v - or 50% of the power is used/lost between the start and the end.  Then you may have another vendor that has 12v RGB nodes that have a 3v drop over the 100 count string.  Again, this could be due to a number of factors - power consumption/design of each LED, gauge of the wire, quality of the circuit board, the type of solder used, the number of strands in the wire, the type of wire (100% copper, tin coated copper, tin only, etc.)  So, unless your vendor provides SPECIFIC information on how much power, over a given length at a given voltage the lights use - YOU MUST TEST AND MEASURE THEM YOURSELF!  Don't go by estimates or guesses - only trust the data.  When you've collected the power consumption amounts, you should then have a amperage (at a given voltage) or wattage for the number of lights or length of lights.  An example of this may be 37 watts per 5 meters of RGB strip.
• Additional information:  You should always measure current draw with ALL colors on, so for RGB lights this means the light will be "white" in color.  Ideally you should leave the all lights on over a period of time (an hour or so) to get a true measurement as resistance goes up (along with higher power consumption) as the wires and lights heat up.
• Controller
• Purpose:  A controller is designed to rapidly turn off and on the power going to a light to create the impression of "dimming" - it does this usually through a process called Pulse Width Modulation.  
• Selection:  Once you have selected your light type, then you've tested the power consumption, you can then determine which controller will be able to handle those lights.  Controllers are rated in amps or watts - which are the same thing when amps is combined with a given voltage.  So, if your vendor says that the controller can handle "6 amps per RGB channel" they mean that there are three individual DMX channels, each which can handle 2 amps - or a Three Channel DMX Controller.  The key here is - what is the voltage, so the voltage would be, say 12 volts, so if we use Ohms law, we come up with:  12v * 2amps = 24 watts, so this controller would handle 24 watts of power for each output or 72 watts per RGB channel (3 channels.)  So, if you've selected lights that you've TESTED to be 100 watts per "string" when they are lit up as white, than that single RGB output on the controller used in the prior example (72 watts) would not be sufficient to handle the load and you would either need to reduce the number of lights (less likely if the lights were planned correctly) or you would then need to divide up the load with either an additional controller or a multi-channel controller such as a 27 DMX channel / 9 RGB channel DMX controller.
• Additional information:  Controller terminology comes in all different forms here are some of the common terms:
• Channel:  Usually this refers to a single, two connection (wire, solder pad or screw terminal) output tied to a single DMX channel.  So a three channel controller would have three of these outputs and would also have three corresponding DMX channels.
• RGB Channel:  An RGB channel is the same thing as a three channel controller - it means that with each of the three channels, red, green and blue can be controlled to make most any color.
• DMX Channel:  This is a single output usually, that can be adjusted from a level of 0/zero/off all the way up to 255/on.
• Additional information:  It doesn't make any difference if the controller is a pixel/smart controller or dumb controller - they both use power in the same way the only difference being that one can control each light individually vs all lights at the same time.
• Power Wiring
• Purpose:  Power wiring transports the power from the power supply to the controller.
• Selection:  This selection is usually pretty easy and "by the numbers".  Those numbers are determined by the TOTAL power consumption of ALL the LEDs attached to the controller or controllers at the other end of the power cable - it has nothing to do with your controller because if you've properly allocated the maximum number of LEDs to your controller(s), than you just add them all up.  So, if you have two controllers, each with 50 watts of LEDs, you need a power cable able to handle 100 watts.  So, how do you select a cable that can handle 100 watts?  That depends on the distance to the controller.  So, these two factors - the amount of power you need to carry and the distance between the power supply and the controller(s) - we've covered this exact topic in our blog post about RGB wiring selection - check there for additional information and wiring selection charts.
• Power Supply
• Purpose:  To provide sufficient power at the correct voltage to the controller to power the lights.
• Selection:  Power supply selection is the last item to select and is pretty simple based on a few factors, such as:
• Total power consumption:  That same amount of power consumption that was determined in the power wiring section (the total power consumption of all the LEDs connected to the controller(s)) applies completely to the power supply.  If all your LEDs require 100 watts, you'll need AT LEAST a 100 watt power supply, though usually a 10 to 20% overhead is a good idea.
• Form factor:  Power supplies can be purchased in many different forms - from waterproof, to water resistant to open frame.  Mainly this has to do with how you intend to use the power supply.  If the lights are inside, a simple shrouded power supply will be fine - no need for waterproof but if you are mounting it outside in a high humidity environment, you may be better off with a waterproof power supply.  Also consider how you'll attach or mount the power supply.  Also consider air flow as high wattage (250w +) power supplies often have fans and need a sufficient volume of air for cooling.
• Voltage:  Of course the lights you selected at the start will be a given voltage and thus this applies to the power supply.  So, if you have 12v lights, you'll mostly likely need a 12v power supply.

We hope this helps you in the selection of the right wiring, power supply, controller capacity and lights for your project.  Here are some other related blog articles:

• See the effects of power consumption on the output of pixels
• How to outline your house in pixels
• Smart Pixels or Dumb RGB lights - which is right for me?