Backlighting laser etched fascia panel

[David Hymers]

Hi.

I'm currently making a car dashboard for my race-sim cockpit. It is made from abs, petg and acrylic all laser cut. I want the dashboard's fascia to "glow" and am planning to use some elctroluminescent sheet to accomplish this. I've been looking at a number of options for the fascia panel itself and am leaning towards using some matt black reverse lasermark from Rowmark.

Does anyone here know if that is a suitable product for this purpose and if the finish on the cap side is good enough to be used as the facing side of the fascia? Or can anyone enlighten me as to a better way of backlighting? I have searched and searched and searched and still don't know what the best method for backlighting is. Ideally I want the text to be white until the dashboard is switched on at which point the text will glow - and in different colours!

I figure back-painting the reverselaser sheet with white and then placing various coloured transluscent sheets behind that and finally lighting that all up with a white electroluminescent sheet. I have no idea if this would work.

I would love any advice at all from anyone.

Thanks.

[Rodne Gold]

The best way is to laser the legend in the reverse black/clear rowmark , the text will naturally be white , then add 6mm pex strips which you have lasered to a frosty finish behind the text and side light the pex itself , the frosty strips will glow the same colour as the leds and will light up the text.

You can have 2 leds sidelighting the strips , one white and another colour , when switched off the white led can light , making the letters and legend glow white , once you switch on , switch to the other led and the text/legend will glow the led colour.

[Dan Hintz]

If you want different colors, LEDs are the way to go (side-lit acrylic is dirt easy). EL is a single color and once you cut it to shape you can't change it... with LEDs, you can change the acrylic backer shape all you want without needing to throw away the lighting. Not to mention EL panels use a high-voltage, high-frequency ballast that can wreak havoc with non-shielded, sensitive electronics that are in proximity (such as might be the case with a race simulator where low-voltage sensors are used for input). LEDs also allow you to put the lighting component out of the way (i.e., along the edge), rather than with EL, which requires close proximity to what's being lit (e.g., middle of the panel where siwtches might be in the way).

[David Hymers]

Gentlemen, I am both very grateful and intrigued by your answers. I particularly like the idea of LED lighting because this will be much cheaper than electroluminescent lighting! :):)


laser the legend in the reverse black/clear rowmark , the text will naturally be white

Will the text be naturally white due to the lasering process? Will this be clearly legible in a room under normal incadescent lighting (without the LED backlighting being switched on)?

The reason I ask is because I want this to be legible under normal ambient incadescent lighting conditions but also have the option of switching on the LEDs for the glow effect - if desired (as opposed to being necessary). The two colors I referred to will be blue and red, both being on at the same time. Some parts will be red in color when lit, some blue.

I assume 6mm pex is perspex? That is acrylic? Please forgive my ignorance of industry slang. We were all newbies once! I am curious as to why the pex needs to be frosted behind the text. Is this necessary behind the text only? Also, and this is the most important part - will side lighting the pex give an even light right across the panel? This panel will be about 420mm (16-1/2") wide. I can light it from both ends.

The unfortunate part is that I only have a maximum of 2mm behind the fascia panel for lighting. The Rowmark fascia itself will be 1.3mm thick and then there's a mere 2mm space behind that. The restriction comes from the length of the little spindles poking out the end of the air-core drivers that physically move the gauge's needle. Will edge lighting a 2mm sheet be possible/work?


Thank you so much.

[Rodne Gold]

Will the text be naturally white due to the lasering process? Will this be clearly legible in a room under normal incadescent lighting (without the LED backlighting being switched on)?

Yes it will be legible , it comes out nice an frosty if you use the Rowmark laserable suff , easily visible in normal lighting.

The reason I ask is because I want this to be legible under normal ambient incadescent lighting conditions but also have the option of switching on the LEDs for the glow effect - if desired (as opposed to being necessary). The two colors I referred to will be blue and red, both being on at the same time. Some parts will be red in color when lit, some blue.

It will be fine for that

I assume 6mm pex is perspex? That is acrylic? Please forgive my ignorance of industry slang. We were all newbies once! I am curious as to why the pex needs to be frosted behind the text. Is this necessary behind the text only?

Yes , 6mm acrylic .. the thicker you can go the better the light transmission - the frosting is to make the surface "glow" , without it , the pex is almost transparent even when sidelit - I would frost the whole piece.

Also, and this is the most important part - will side lighting the pex give an even light right across the panel? This panel will be about 420mm (16-1/2") wide. I can light it from both ends.

There is fade over distance , you will have to see whether the led you choose or the strip of leds is ok for this , you might have to light both sides , reflective silver vinyl applied to the edge of the piece you are lighting acts like a mirror reflector of sorts and makes the lighting more even too - leds have "spread" of light too that have to be considered
What we have done in the past where the panel was lit from one side only and the evenness of the light was important across the whole panel was to engrave a faded halftone , so that where the light is strong there are less dots to luminesce and as it goes further we engrave more dots so the panel lighting appears even
We have a flat surface mount led that changes to 7 colours and can be programmed to fade or flip between em and all other stuff - that would make for great sidelighting - but they really pricey - a 8 led 25cm strip is like $40 and you need a power source etc.
Im not a led expert so cant really guide you here as to what to use.

The unfortunate part is that I only have a maximum of 2mm behind the fascia panel for lighting. The Rowmark fascia itself will be 1.3mm thick and then there's a mere 2mm space behind that. The restriction comes from the length of the little spindles poking out the end of the air-core drivers that physically move the gauge's needle. Will edge lighting a 2mm sheet be possible/work?

Be real difficult...You can try , I would rather go at least 3mm and even thats a little marginal.

[Dan Hintz]

The two colors I referred to will be blue and red, both being on at the same time. Some parts will be red in color when lit, some blue.
You will need to separate each colored portion into its own piece to prevent spillage of one color into those surrounding it. Cover the edges between pieces with black paint, tape, etc.

The unfortunate part is that I only have a maximum of 2mm behind the fascia panel for lighting. The Rowmark fascia itself will be 1.3mm thick and then there's a mere 2mm space behind that. Will edge lighting a 2mm sheet be possible/work?
2mm isn't a problem, but it may require extra work if you do not use thin surface-mount (SMD) LEDs. SMD LEDs can be easily found with faces <2mm in height (used most often in cellphones, PDAs, etc.). If you're stuck with through-hole LEDs, you'll need to "funnel" the light into the edge of the sheet using either a plexiglass optical wedge or surrounding the LEDs/edge with reflecting tape. You'll lose a lot less light with the plexi wedge, but sometimes you don't have the space.

[David Hymers]

Wow. Thanks chaps. :D It sure sounds like LEDs are the way forward. And heaps cheaper than EL sheet. :cool:

I have a really daft question about side lighting. I've been looking around for SMD LEDs and found plenty. Some are "right angle", some are not. The ones that are not shine up and away from the pcb they're mounted on. Here's the dumb question. Do I literally side light the acrylic sheet - ie shine the LED through the edge of the sheet and in a direction towards the center of the sheet? If that's the case then the surface mounted LEDs that shine straight up from the pcb will not be of any use unless the pcb is mounted vertically from the acrylic surface and parallel with the sides of the sheet. Yet they seem to be the most popular.

For different colors could I not use a white LED and simply place a thin layer of colored translucent sheet between the acrylic backlight and the laser engraved Rowmark cap layer? It would mean I can make a simple square shape for each gauge (and light them independantly) - the colored translucent sheet overlay providing the desired color in the desired location.

Exactly how many of these little LEDs are required? Do you have a rough idea? I mean, does one LED light up a whole square foot or would one only light up a square inch or so? I also read on another thread that the edges of the acrylic ought to cnc cut or at least frosted as well. Is that true?

I can't thank you guys enough for the help! I have extensively searched for this sort of information (to an unhealthy degree according to the missus) and got nowhere really.

[Dan Hintz]

I have a really daft question about side lighting. I've been looking around for SMD LEDs and found plenty. Some are "right angle", some are not. The ones that are not shine up and away from the pcb they're mounted on. Here's the dumb question. Do I literally side light the acrylic sheet - ie shine the LED through the edge of the sheet and in a direction towards the center of the sheet? If that's the case then the surface mounted LEDs that shine straight up from the pcb will not be of any use unless the pcb is mounted vertically from the acrylic surface and parallel with the sides of the sheet. Yet they seem to be the most popular.

For different colors could I not use a white LED and simply place a thin layer of colored translucent sheet between the acrylic backlight and the laser engraved Rowmark cap layer? It would mean I can make a simple square shape for each gauge (and light them independantly) - the colored translucent sheet overlay providing the desired color in the desired location.

Exactly how many of these little LEDs are required? Do you have a rough idea? I mean, does one LED light up a whole square foot or would one only light up a square inch or so? I also read on another thread that the edges of the acrylic ought to cnc cut or at least frosted as well. Is that true?
Yes, through the edge... the closer to the edge you are, the better. If you cut the edge of the sheet at a 45 degree angle (which acts as a mirror), then you can use the forward-firing LEDs mounted to a PCB, else use the side-firing type.

You can use a white LED with a colored acrylic cover only if the LED is made up of red, green, and blue dice. The typical white LED is usually a blue die with a yellow-emissive phosphour coating, which fools the human eye into thinking it's white. Since you only have blue and yellow wavelengths, some colors will not come out correctly when using colored filters... blue would be okay, red would end up more of an orange. That said, if your application requires a lot of areas in different colors, the RGB LED and filters would probably prove less expensive with less hassles.

Distance to light is based heavily upon the brightness of the LED you're using. My Windscreen Lights product used to use only two RGB LEDs and would fully light a windscreen roughly 10" x 24". Only frost what you want to glow... if you frost the edges, they'll glow and you'll lose light. Tape the edges with silver tape, as Rodney suggested.