Backlit Panels? - Page 1
Forum section: electronics / projects

author: Falcon69
author_rank: Super Contributor
timestamp: September 11, 2015, 11:31:44 pm
content: Hello,I have a project I'm trying to work on, but ran into a snag.I need something that is kind of like a two way mirror, but in black and not reflective.Basically, I have a panel of plastic. It is silk-screened black with reversed words/graphics. I need the words/graphics to be only noticeable when a LED is turned on from behind them.Exactly like how your check engine light or oil light comes on in your vehicle. How do they do that? You can't see them, until the LED or bulb is turned on behind them. Would, perhaps, window tinting film work for that?It needs to be no more then 1/16 inch thick or 1.5mm thick.Thanks in advance.

author: fivefish
author_rank: Frequent Contributor
timestamp: September 12, 2015, 12:42:35 am
content: A 2-way tinted acrylic sounds like what you need.http://www.tapplastics.com/product/plastics/cut_to_size_plastic/two_way_mirrored_acrylic/558

author: Psi
author_rank: Super Contributor
timestamp: September 12, 2015, 12:56:08 am
content: You want a thin black sheet which looks black but a little light does pass through it. (Like very dark sunglasses) This goes on the outside.Then you want a true 100% opaque black plastic sheet with the letters cut out or transparent (what you already have)Then you need a sealed container to put it in so no external light can get in.Lastly you want a LED inside that is quite bright, to overcome the losses getting through the front black sheet.

author: Falcon69
author_rank: Super Contributor
timestamp: September 12, 2015, 12:57:51 am
content: yes, i was down there looking at it this morning. I don't want the reflectiveness (mirror) of it. I thought about maybe a Dark smoke color acrylic or film, but, I think you'd still be able to see what was behind it (i.e. the LED itself or the capacitors/resistors, etc. behind it).

author: Falcon69
author_rank: Super Contributor
timestamp: September 12, 2015, 12:58:40 am
content: Psi,Do You have an example picture showing that with an LED behind it, on or off?

author: Psi
author_rank: Super Contributor
timestamp: September 12, 2015, 01:01:18 am
content: I don't have an example picture no.I've not tried it myself, but it will work.That's how the car dashs do it, except they combine the two layers into one. There's a sealed compartment with the lamp inside (so its 100% dark when the light is off) and then there's plastic on the outside which is 100% black in some areas and 80% black where they want the text/symbol to shine through. When the lamp is off it just looks black and you can't tell the difference between the 100% and 80% black areas.You do need to spec the 80% black substance so it doesn't filter any of the colors, unless you want that

author: Falcon69
author_rank: Super Contributor
timestamp: September 12, 2015, 01:06:59 am
content: ya, i don't want the colors filtered. There will be different colored LED's behind it. Depending on what state the electronics are in.So I need 80% Black Opaque then? Tap Plastics does not have that, nor do they have it in 1/16" size or less. Needs to be acrylic so I can cut it on the laser cutter.

author: Psi
author_rank: Super Contributor
timestamp: September 12, 2015, 01:07:42 am
content: I just picked 80% out of my head.You'll need to try it and see what works.You want as low as possible while still remaining invisible when the light is offIf it were me, i would try coating acrylic with various types of car window tinting film.That stuff comes in lots of grades of transparency.

author: Falcon69
author_rank: Super Contributor
timestamp: September 12, 2015, 01:12:31 am
content: that may work. I can do a layer of 1/16 black acrylic, cut out with the words/ Then use a piece of clear acrylic with the window tint film on the other side. Then glue them all together. Hmm, I wonder if I can cut the tint on my laser cutter. I'm guessing probably not, it's probably made from Poly-carbonate or something.I'll head up to the auto store and see if they have some 60-80%

author: Psi
author_rank: Super Contributor
timestamp: September 12, 2015, 01:20:37 am
content: Quote from: Falcon69 on September 12, 2015, 01:12:31 amThe tinting is a thin film that's sticky on one side. Probably comes on a roll like Christmas wrapping paper but i cant say ive seen it.Should be able to cut it no probs