1. SMD vs DIP LEDS
LED displays generally have two different kinds of LEDs. Surface mounted device and dual in-line pin are the two different ways to package LED chips. SMD is a newer technology and is now about the same price as DIP. It provides a greater viewing angle, higher resolution (as they can be made smaller so you can fit more LEDs into your display), and depending on the manufacturer may not be as good outdoors. DIP LEDs generally can’t go smaller than 10mm pitch because each pixel is made up of 3 separate LEDs (1R1G1B). DIP have been around for a lot longer and are seen as very reliable and bright, and have a smaller viewing angle due to the lens of the LED packaging being much sharper than an SMD LED.
2. LED chips
There are many different brands of LED chips, Osram, Cree, Epistar, Nichia, Philips, Silan, and Sanan to name a few of the most popular. Chips are made all over the world with the main manufacturers in the US, China, and Japan. The LED chips are the actual light emitting diode(s) itself and the quality of the chip will affect such things as: color uniformity, brightness loss over time, brightness capacity, stability, and viewing angle. Drastic differences in price of an LED display can come down to what brand of chips are being used.
3. LED packaging (encapsulation)
How the LED chip is packaged affects the quality of light that comes from the LED, the viewing angle, the weather resistance, the level of heat transfer and other factors. Is it packaged with silicone which helps with heat transfer leading to longer life span, or is it epoxy which doesn’t transfer heat as well? Is it creating white light via a blue LED chip with a yellow phosphor coating, or is it utilising 3 LED chips (red, blue, and green) to do so? The quality of each of the components used to construct the LED will determine how long your LEDs will last, and the quality of the light being emitted. You may even find some suppliers boasting about the LED chips they use, but the LED packaging may be substandard so this chip won’t be properly housed and thus you won’t get the quality and longevity expected from the LED chip. As you can see from the diagram below of an SMD LED, the packaging is multi layered and each of these layers can be made from different quality materials. Also, the quality of the process in which the LED is put together is vitally important. It’s just like building a house, you might have the best quality materials, but if you cut corners in construction, over time this will show in a leaky roof, or other problems.
4. Warranty
How long you are protected from things going wrong with your LED display is vitally important. Even amidst prices dropping significantly in recent years, LED displays are still quite an investment. Electronics tend to have higher error rates at the start and end of their lifecycle, so quality LED display manufacturers will “age” their displays before selling them allowing errors to happen so they can be remedied. Having a 1 year warranty on your LED display is not enough, and you should require a minimum of 2 years for parts AND labour. After the 2 year mark the rate of problems has flattened and you are generally only susceptible to spontaneous random problems that can still happen with electronics today (like when your smart phone or internet browser freezes and you have to reboot). How long a warranty is will affect the price of the LED display.
5. Pixel Pitch
Pixel pitch is the distance between each pixel in millimetres. The lower the pitch, the higher the resolution/definition (more LEDs are being crammed into the same area). Are people willing to pay more for an ultra HD 4K TV than a standard high definition TV? Yes. However, because the viewing distances can vary greatly with outdoor LED displays it isn’t completely comparable to TV definitions where the viewing distance is pretty much always less than 30 feet. From 100 feet away an ultra HD 4K TV and an HD TV would look exactly the same to the human eye. For a large billboard sign beside a highway, you would be throwing money away if you got a pixel pitch less than 10mm as no one would be able to tell the difference who is driving by. However, if you have a sign outside your church and people walk right by it, then you could go lower than P10 and that would still be worthwhile. So obviously this will be a big factor in the price of an LED display, if one business is giving you a quote for P16 this will be a lot cheaper than another business which is offering you a higher resolution screen of P10.
6. Software and Connectivity
Different electronic message centres will use different software to control the displays. Not all software is created equal and you will want to ensure that what you want to do with your new LED display can actually be done with the software provided for the sign. Also, if you want to connect wirelessly to your sign from your building, or home for that matter, you will want to make sure the sign has this capability before purchasing it. As technology is continually reaching new frontiers, more and more capabilities are being built into LED displays and the software accompanying them.
7. Loss of brightness over time (attenuation)
Loss of brightness (lumens) over time for LEDS is directly related to the temperatures they are consistently exposed to. The ability of an LED to dissipate heat comes down to chip quality, phosphor, and whether or not the heat is able to be released smoothly through the pins and packaging. Also if driving current is greater than the rated value the LEDs will be running on overdrive and heating up more than they are made for which will result in an increased rate of attenuation. Knowing that your LEDs are going to last for years and will still be able to be viewed in bright sunlight is crucial to the effectiveness of your sign. This rate of attenuation is affected by quality of the LED and it’s component, the way the sign is built and protected from weather, and it’s ability to remain cool as heat is the greatest factor in attenuation rates.
8. Brightness
Different LEDs are designed to be able to emit differing levels of brightness. If you are going to have an outdoor LED display that faces direct sunlight you will want it to have a brightness of over 6000nits. For indoor you only need around 1000nits (up to 2500nits if indoor and still in direct sunlight). For outdoor signage where ambient light is continually changing, you will need to have a light sensor that will auto dim your screen according to the current brightness of the environment so that your LED screen isn’t blinding passersby because it is still displaying maximum brightness even though it is the middle of the night! One thing to be aware of is that with LEDs that aren’t rated for high brightness, you can still reach extreme brightness levels by increasing the power to the LED, this will work fine in the short term but will lead to them losing their brightness rapidly over time as they aren’t designed to operate at that level.
9. Contrast
Brightness isn’t everything. The sun’s brightness when viewed directly is around 60,000nits, if you had a completely reflective sign, then no matter how high you managed to get your LEDs nits, it would still be overpowered by the sun. So reducing reflectivity of LED displays is important so that the contrast ratio is suitable. Contrast ratio is the ratio of white to black. The higher the contrast ratio the more readable the content of the display, just like reading white letters on a black background is easier to read than grey letters on a black background. In the below image you can see that the display on the right has a higher contrast ratio (the difference between the darkest black and the whitest white is greater) leading to a crisper image, even though both screens are still just as “bright”. The implications of a good contrast ratio are significant, as it means you can run your LEDs at a lower brightness and get the same readability which will reduce the heat of the LEDs leading to increased longevity and power savings!
10. Cooling
Considering that heat is the main contributor to the degradation of LEDS and their level of brightness, the ability for the sign to remain cool is very important. There are many different ways to cool the sign, from simply having vents in the LED display cabinet, to having fans that cool the display, to air conditioning untis inside the cabinet, to having higher quality components in the LED itself and the PCB to help with heat transfer. A sign that has air conditioning units compared to one that just has some simple fans (pictured below) is going to be a lot more expensive!
Now you have a glimpse into the world of LED displays and how these aren’t simple products that are easily comparable. Make sure you talk to someone who knows the ins and outs of LED displays when you decide to step into the future of signage with your very own Electronic Message Centre. Click here to see photos and videos of some of our Electronic Message Centres. Jordan Taylor 905 802 5741
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