Friday, December 22, 2017

Why its NOT Time to buy LED Projectors

LED (Light Emitting Diode) Projectors are on the market.  They have been for a few years now.  At first they were waffling between LED and Laser(which uses LED) and have settled on LED for the most part.  
LED pocket projector


LED is touted as "No more lamps!" which is the biggest selling point.

Is this true?  Its true that there is no lamp to replace in an LED projector.  They have no removable user parts that can be replaced. Its a sealed unit and you are at the mercy of the manufacturer.

Is this a good thing?  In my opinion, as it stands now, I say its not a good thing.  There is a lot of promise in LEDs.  They are not the lifetime lamp they claim to be.  

Being someone who works inside projectors, its been my experience that LEDs are not there yet. 

I will explain my thought and will be interested to see if my thoughts hold true in a few years.

LEDs themselves are fine. For general lighting, indicator lights and even low lumen, low cost projectors.  

Inside a projector, the LED light engine is made up of 3 chips(In most cases). I'll be referring to LEDs as Chips since they are semiconductors.


RGB LED chips
They use a Red, Green and Blue High output chip mounted to a large heat-sink arrangement.  Those Chips are then powered by a special lamp driver made to run those Chips .

Current LEDs suffer from a problem that cause them to have a severe drop off in brightness after a certain point.  That energy then becomes heat.   The average short arc (current technology)projector is 3000-5000 lumens at 250-300watt.


For instance, the Optoma UHD60 uses a 240W Osram bulb that puts out 3000 lumens to the screen.  This means the unit uses 240W of lamp power(not 240W total power) to drive the lamp.

An LED for the same unit would need to be at least 50W per color.  That would then add up to 150W total (for RGB). The problem here is that at 50W the Chip is going to generate a lot of heat and put a lot of stress on the lamp driver.  In most cases when an LED light of any type(even incandescent replacements in your home) fails, its because of the lamp driver rather than the LED element itself.

The amount of thermal stress increases greatly as the wattage increases.  Most of the time the voltage is constant and the amperage is increased. 

Over a few amps, the thermal reliability begins to drop off significantly.  The diagram below shows the drop off of a high power Blue Chip that could be used in a projector.

Blue LED efficiency chart
Short Arc Mercury lamps such as the BL-FP240E for the above mentioned Optoma UHD60 and UHD65 on the other hand are tried and true technology.  When the lamp fails in this model you can change it.  That lamp usually lasts 2 years(with normal use). Then for a few hundred bucks you are back in operation and have a nice bright image.
Optoma UHD60 UHD65 4K Video Projector image

If you want to use a long throw projector in an auditorium you are definitely better off with the current type of projector technology over LED. Even Laser which is advertised as effective will not give you the clarity and color rendering that a Short Arc lamp can currently deliver.

With the average LED projector warranty only being 2 years, you are then stuck with a multi-thousand dollar paperweight when the lamp driver fails or the LED overheats.  There is no reset or simple bloated capacitor fix.  It is going to need a new lamp driver module and probably a new LED module.  In my experience those parts can be much higher costing than a plain old short-arc lamp.

Last projector I worked on with LEDs, would have cost $300 for three 25 watt red, green and blue chips.  It still needed a lamp driver which was $150.  For the low-low price of $450, the customer would then have had their $315 LED projector back in operation.  Lesson learned.

Those lamp drivers and Chips are not user replaceable. There is no door you can open and pull a cartridge out and then pop in a new one.  You have to take the projector down, ship it to a repair center and wait for it to be sent back. Inevitably it will fail again.  Rinse and repeat.

With LEDs now starting to grow up, I fully believe they will be the light source of the future.

However as it stands now, they are not there yet.  Don't let yourself be part of the manufacturers experiments.  Wait until you see a 4K 3000 lumen projector under $1000.
https://www.purelandsupply.com/optoma-projector-lamp_bl-fp240e.html

Until then buy an Optoma UHD60 or UHD65 and then in 2 years check back to see how BL-FP240E is going for and let me know if I was right about LEDs.








Happy Holidays from Pureland Supply! Have a Safe and Pleasant Holiday Season!


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