Cost of optic for LED lamp is massively high?

[treez]

Hello,

Please help us because we must now scrap our product because the LEDs are going obsolete.

..Our LED lamp product is based on these 63V, 40mA LEDs (SAW09H0A & SAW09A0A)

SAW09H0A
http://www.mouser.com/ds/2/363/SAW09H0A-334993.pdf

SAW09A0A
http://www.seoulsemicon.com/upload2/MJT4040_SAW09A0A_Rev2.0.pdf


Unfortunately these LEDs are about to go obsolete. Our boss now says that the entire product will have to be scrapped, because in order to continue it, the optic and LED PCB would have to be re-designed to accommodate whichever new replacement LEDs might be useable. He says that this would cost a massive amount of money, and that therefore the product must simply be scrapped. Is this right? The cost of getting a new optic (arrangement of lenses molded into a transparent Perspex sheet which covers the LEDs) is that hugely expensive?

The following LED could replace the SAW09H0A…..
Luxeon 3014
http://www.lumileds.com/uploads/459/DS208-pdf

 

[betwixt]

The Luxeon is a much lower power device so you would need more per enclosure to get the same total light out. That obviously means a different distribution on the circuit board.

However, it seems you are not designing for best flexibility. There will almost always be component sourcing problems on 'new tech' devices and as you have discovered, parts go obsolete rapidly. I sounds as though you have optics dedicated to one manufacturers product which puts you at their mercy and forces you to buy at a price they control. A far better strategy is to design the optic the other way around - start with the luminous 'footprint' you want and design a general purpose lens that gives you flexibility to change the LED type and layout. A new PCB in an existing enclosure is far cheaper to implement than having to design and make acrylic molds as well.

Brian.

 

[treez]

A far better strategy is to design the optic the other way around - start with the luminous 'footprint' you want and design a general purpose lens that gives you flexibility to change the LED type and layout.

Thanks, this sounds like a great idea. I am wondering if there is a “most common” type of white power LED package that we could pick?
Then as you say we wouldn’t need to keep re-designing the optic every time the LED went obsolete.
With other components, diodes, resistors etc, they come in standard packages, (eg 0805 etc), but LEDs don’t seem to have this standardization?

 

[betwixt]

I don't think the LED package is an issue, at least as far as PCB layout is concerned, it's the light distribution that matters.

If you design backwards from the desired outside radiation pattern you should be able to come up with something that allows numerous internal LED placings to give roughly the same output. Doing so would allow the use of a common optic lens when the internal PCB and LED design changes. I'm thinking along the lines of an optic with narrow prismatic pattern on the inside that deflects light mostly from the middle to the sides. I'm assuming this is for street lighting where the pattern would be along the length of the street with a little radiating 'forward' to fill in the other side. A common lens design let you change the light source at lowest cost with little effect visible form the outside.

We have a problem with LED street lighting in my village at the moment. They appear to have two blocks of seven LEDs in them, presumably these blocks could be used individually or grouped for more output. The arrangement is two rows of three and one extra in the middle on one side. The light dispersion is very poor, so much so that they cast multiple shadows, one from each LED if something passes before them. Where there are trees nearby (and I'm in Snowdonia where there are a lot of trees!) each branch casts its own shadow and the whole scene animates when they sway in the wind. With the old LP sodium lighting it wasn't a problem but now it makes it difficult to see the street layout, particularly to pedestrians who have no headlights of course, as the ground appears to be constantly moving. Each branch casts seven individual shadows that interact depending on which LED they obscure.

Brian.

 

[treez]

If you design backwards from the desired outside radiation pattern you should be able to come up with something that allows numerous internal LED placings to give roughly the same output. Doing so would allow the use of a common optic lens when the internal PCB and LED design changes.

Thanks, this sounds good, and confirms to me that we needn’t scrap this product at all. All we need to do is design a “general” optic for it, and use any of a large number of LEDs which go under such an optic. Admittedly we’d have to get the LED PCB redone every time a LED goes obsolete…..but that isn’t too expensive…and the LED manufacturers always give 2 years warning before an LED line is about to go obsolete.
Also, I am pretty sure that you can buy individual acrylic optics, and cheaply get these infused into a sheet of clear plastic to make a really cheap optic for a multiple LED PCB……won’t be super-perfect, but surely perfectly satisfactory?

I dont know why we have plans to scrap the product range over this.

 

[volker@muehlhaus]

Also, I am pretty sure that you can buy individual acrylic optics, and cheaply get these infused into a sheet of clear plastic to make a really cheap optic for a multiple LED PCB……won’t be super-perfect, but surely perfectly satisfactory?

Doesn't the focal length change when the lens is embedded into material with other refractive index than air?

 

[BradtheRad]

an optic with narrow prismatic pattern on the inside that deflects light mostly from the middle to the sides.

Possibly like a skylight used on ship decks? Whatever angle sunlight came from, the prism distributed it around the room below.



- - - Updated - - -

(The photo was flipped for some reason. So the wood should be the ceiling.)