A Brief History of LED Signs
At their essence, outdoor LED signs are simply signs that include a display, or “message center” made up of light emitting diodes (LEDs) to form text, graphics, or animations as a marketing tool. Although it may seem like a no-brainer, to answer the question “What is an outdoor programmable LED sign?” in detail, but it is not so simple. A general understanding of the history, technology, and variables in the outdoor LED sign industry are necessary to be able to understand the whole answer to this question. Armed with this knowledge you can find yourself in the driver’s seat if you are seeking to plan a sign project of your own. The following points are intended to describe in detail each of the most important variables to consider when defining what your outdoor programmable LED sign should, or could have depending on your specific needs and preferences.
#1: The History of LED Signs:
Light emitting diodes have been around for a very long time. A Russian scientist named Oleg Losev reported the first discovery and creation of light emitting diode technology in 1927. However, there was no significant application of the technology for decades until in 1961 James R. Baird and Gary Pittman of Texas Instruments in Texas were able to demonstrate that LED technology could be made into a commercial product. In 1963, Texas Instruments announced the commercial LED product, but the light emitted was not readily visible. During this same time period, General Electric was running its own experiments resulting in the announcement of the first LED capable of producing a visible light spectrum in the December of 1962 issue of Applied Physics. By 1972 General Electric improved the brightness of their LED tenfold.
In the 1960s a single LED diode capable of emitting visible light cost $200 per unit. These diodes were only used in medical equipment and other high technology devices requiring little to no heat output with reliable light emission. By the 1970s LEDs were used in calculators, radios, TVs and other appliances thanks to Hewlett Packard’s work in making the technology more affordable and practical for commercial uses.
The First LED display:
The work at Hewlett Packard that made LEDs more practical for commercial applications was headed by Mohamed M. Atalla in collaboration with Monsanto to produce the first programmable LED display at HP. It was considered a revolution in technology at the time as the world’s first intelligent display. Atalla’s methods from this time period are still used in LED production systems to this day. The diodes in these devices were still quite dim, and red was the only color until a bright blue was obtained through increased innovation in the chemistry of semiconductor technology as it pertains to light production. Diodes were covered by a colored lens to produce a specific unchanging color. Today, LEDs are produced in Red, Green, Blue, or all three in one diode in the case of SMDs or Surface Mount Diodes which are used in today’s outdoor LED signs with definitions of 10mm or lower. This is required in order to fit the diodes closer together and thus create a higher definition image.
#2: The Main Components of Outdoor LED Signs
All outdoor programmable LED signs have the same basic components at their core. Other features, components, and the like can be added. The additional components and/or features can often be used to cloud one’s understanding of an LED sign’s value. So, it is a great idea to understand the basics that will allow you to ask the hard questions.
All outdoor LED signs have diodes. But not all diodes are made the same. An important quality indicator of a diode is the brightness level rating. As diodes are produced they are dropped into “bins” to sort them by their brightness quality. This is the best way to tell diode quality, as long as the same amount of electricity is provided to the diodes being tested. The problem in today’s outdoor LED sign industry is that many manufacturers use cheaper diodes with lower brightness ratings to save money, which is fine in and of itself. However, these companies then configure the power supplies in their signs to push extra electricity to the diodes making them brighter for the short term. The problem with this method is that it forces the diodes to degrade much quicker than they would have under normal electrical conditions. So, if you have a sign that is claiming 10,000 NIT brightness, you may want to dig deeper. Diode manufacturers producing 10,000 NIT diodes are proud of their product and the manufacturers that spend the premium price to use these diodes are equally proud and willing to disclose where their diodes are coming from. Some examples are Nichia, Cree, Osram, Lumileds and others.
Programmable outdoor LED signs are always going to need to mount to some sort of support structure that houses the internal components and provide a safe system for the LED modules to mount to. Low quality cabinets are made from steel and allow for water to leak in. Steel rusts, so it is inevitable that water infiltration will be a problem for these signs. Most moderate to high quality manufacturers are using aluminum cabinets to avoid problems related to oxidation. These cabinets should be painted with sign grade paints like Matthes PAint, or Akzo Nobel paints. Some cabinets are powder coated as well.
Power supplies accompany just about every electrical appliance or device in operation today. The purpose of a power supply at its essence is to receive power from the raw source circuit and condition that current to a specific configuration to serve the purposes of the destination where the power is actually sent from the power supply itself. Outdoor LED signs have many types of power supplies, but they should all be judged by their ability to deter the two most common enemies of LED signs; heat and humidity. Overheating and water infiltration can cause degradation and failure in electronic components. IP Ratings are often used to measure the ability of a component to suppress or prohibit water infiltration. Look for verified IP67 or IP68 ratings. Independent lab certifications like UL, MET, or ETL among others are useful to verify if a component is going to withstand the heat it will encounter outside in the elements. (see: https://guthmansigns.com/blog/ul-vs-etl-vs-met-listing/)
Of course, electrical components in an outdoor LED sign will need to be connected in some way, and these methods are extremely important to consider and understand. Lower cost options include ribbon cables of varying sizes and specifications. Ribbon cables have many points of contact per cable (over 30 in some cases) creating increased probability of failure. Basically, the rule is that the more points of contact there are, the higher the probability that a failure will occur. Many factories of medium to high quality use more modern connectors with anchoring systems that keep cables from wiggling loose.
Since heat is such a detriment to the longevity of LED signs, it is important to understand the ways manufacturers try to cool their displays. Traditionally, cooling fans have been employed. With these designs, fans are mounted inside the sign cabinets to pull air from one side of the sign and push air out the opposite side, to keep cool air circulating over the internal components. These systems work well, as long as there is enough space between the cabinets so hot air isn’t continually re-circulated back inside the same cabinet.
Another method is the heat sink. These methods are denominated as passive cooling systems since they don’t have any moving parts. They are simply metal ridges protruding from where heat is generated in order to allow heat to dissipate naturally. Again, space is extremely important to allow these signs to stay cool and last their full life expectancy.
LED sign modules are made by mounting diodes to circuit boards and mounting these to varying styles of plastic squares or rectangles that, when placed together and connected to one another, can operate as a full display. The modules are where water infiltration is most dangerous because of the fragile connections that are included on circuit boards and diodes. Lesser quality signs will have no coating at all and the circuit boards often fail quickly for this reason. Medium to high quality signs will have conformal coating (a spray on silicone gel) or potting (poured on silicone) to completely seal the components from water infiltration. Potting is generally much better than conformal coating due to the thickness and robust adhesion it allows for.
#3: Diode Color:
Another important quality indicator of an outdoor LED sign is color. Each diode, whether Red, Green, or Blue, has its own quality and brightness rating. Red diodes are generally the least expensive, and Blue is the most expensive for most circumstances, so a low quality sign manufacturer will often use high quality Red diodes or Green diodes perhaps, but will skimp on the Blue diodes. The result is visible to the passer-by if you look close enough. In specific, pay attention to the whites in the LED display image. If the “white” areas look pink or green in hue, you can be sure the sign is being pushed or “over-driven” with electricity and the other diodes have degraded faster.
In the LED sign industry, control software packages can vary widely. It is an area where many consumers do not pay much attention, and often regret that dearly later on. Some LED signs include very simple software that requires a dedicated laptop supplied by the manufacturer and the sign cannot be controlled otherwise. Others employ software packages that must be downloaded to a local computer tied to the outdoor LED sign by wireless antennas on site. Still other software packages are cloud based, allowing the sign to be controlled from anywhere in the world with an internet connection, including via smart phones, for example. It is essential to understand exactly how you will interact with the sign, thus requesting a demo of the sign software prior to purchase is advisable. Be sure to note whether or not a standard content package is made available in the software, or if custom content is available for order through the software. Note exactly how you will need to manipulate images or animations etc to upload them to the sign as these processes can vary widely in complexity.
Any LED sign will need to connect to a computer to receive the playlist you want shown on the sign. This communication can happen in a variety of ways. The most modern, seamless, and reliable method of communication is via cellular modem. Many factories now offer cellular modems with data plans included so that once the sign is installed, it connects immediately, allowing users to program their outdoor LED signs immediately. Other solutions employ short range wireless antennas with one antenna installed on the sign itself and its pair installed to the building on site. The antenna mounted to the building then needs to be connected via ethernet cable to the router inside the building for this method to work correctly. This requires a direct line of sight and has a distance limitation of anywhere from 300-1,500 feet depending on the provider. Finally, LED signs can be connected with hard wire cat ⅚ cable (the same as your ethernet cable connected to your router in your home or business). Ask yourself which would be best for your circumstance, but if you can manage the $1,200-$1,500 cost increase to add cellular modem, it is often well worth it.