Some Back Lighting Techniques I Used

I was asked to illustrate some backlighting techniques that I am using on several parts of my cockpit build. The CDU, CMSP and NMSP are panels under construction at the moment I have recorded the various stages of development. So on to the backlighting.

I did my backlighting for the CDU as follows. I think it works really well. Unfortunately the photos don't come close to doing it proper justice.

Start with a PCB and tactile switches in place. The switches were chosen for the long posts as they become important as we move along.

Keep in mind that I designed everything in AutoCAD before hand and I use a CNC mill to cut everything. The designed incorporated several layers of boards. After the initial PCB with the tactile switches in place I then make another PCB just for the LEDS. It registers tight to the first PCB and only the tactile switch "POSTS" protrude. Having the LEDS on a separate board does make it easier to assemble as it could get rather crowded doing it all on one board.

This next piece, the acrylic sheet, allows just a bit of the post top to protrude through. When a post is depressed all the way down it is actually flush with the top of the acrylic. So just the "active length" of the post is visible.

This is just a closer look at the acrylic sheet and you can see how it functions. I pocket out areas on the reverse side to allow for the height of the LEDS so they don't interfere with it sitting tight to the PCB.

This pic shows the next piece in this sandwich of parts. It's the acrylic sheet that holds the actual engraved buttons in place. As you can see, the buttons have a lip to hold them from coming out of the CDU. I have pocketed out an area beyond each button hole just deep enough to permit the bottom of the button to sit flush with the underside of the acrylic. This plate with all its buttons in place then sits on top of the previous acrylic piece. Notice the white strips on the underside of the acrylic. They act as shims to hold this button filled plate just high enough so the posts make contact with the underside of the button and still have the needed space to allow the button/post to be depressed.

The push buttons themselves are made from white styrene plastic, around .3" thick. The plastic is first painted and then engraved. Then the whole thing is flipped upside down and hollowed out with the mill. I do this to ensure good light penetration to the underside of the engraved button top. Each push button has a clear cube of acrylic placed inside it to act as the bottom of the button so it will make contact with the tactile switch post. I could have used a solid acrylic button instead of all this hollowing out business and then adding some acrylic cube to it... bit I like the feel of styrene buttons:animals_bunny:. Acrylic buttons just feel to hard.

This next pic shows it lit up but I do not have the push buttons installed yet. I just wanted to see how it looked in terms of lighting. I am going no further on this project until I have found a decent display for it. Then I will make the required cutout for the additional buttons and the display.

And finally, the face-plate and buttons all in place and the backlighting turned on.

It really is sad that I can't get a picture that actually shows how good the backlighting turned out

It may appear as really finicky...all of those pieces to make, but with a CNC mill its pretty much sit back and watch as things get cut to exactly the correct size. Then you just put it together as if it were a kit. The effort is in the design time and ensuring everything is properly registered and no critical overlaps of unforeseen parts.

Next....

When I built the NMSP and the CMSP I used individual circuit boards for each button or a strip PCB. This is what I constructed to allow good backlighting..

First I designed and cut a PCB for the switch. The ones in the pictures are a little wide. I had lots of room so I could screw each one in place. The basic concept was to build an extension of the post around a fixed LED. The LED could sit in the middle of this extension post and not be affected by the movement of the push buttons.

The next part was to cut a 0.02" thick piece of plastic sheet 5mm x 5mm and then glued it to the top of the post of a tactile switch. I then cut 2 small blocks of 0.06"x 0.06"x 5mm long plastic strip and they were glued on to each side of the 5x5mm plate I just finished gluing to the tactile switch post. That little structure will ensure contact is made with the underside of the button. Between those two pieces of plastic is an LED fixed to a circuit board.

These are all of the pieces I use to make this happen. For the actual engraved button, I use exactly the same technique as with the CDU above. Hollowed out styrene with an acrylic block inside it.

I take a 3528 LED and with a sharp blade I bend the tabs out from the bottom as in the sketch I drew. Then its just a matter of soldering on a couple of stiff pieces of bare solid core wire to act as the supports for the LED. There are holes in the PCB next to the switch body for the support wires. I just drop it into place so it sits nicely on top of the plastic plate and between the two little blocks. Thats the position it gets soldered.

The plastic parts move as the switch is depressed. They are the link between the underside of the button and the top of the switch post. The LED is fixed to the PCB and it remains stationary and is not impacted by any movement. And of course the key to all of this is using the same buttons as I did for the CDU (hollowed out with acrylic block inside) or a plane solid acrylic button that's been painted except for the underside. Light penetration is excellent in both cases.

Here is the backside of the CMSP and the backlit push buttons installed.

Guess you might as well see the front although I don't have it turned on in this pic.

And then there is the NMSP where I used this technique to simulate Korry switches. You can see how I bent out the tabs on the LED to solder on to.

And the front. Same as the last one. No lighting on. Sorry. But the backlighting turned out very nice.

And that my friends is how I do my backlighting. I hope that you get some new ideas from this on how you can do something similar or totally different, in which case you will need to post you ideas as well.

Thanks for reading.

Impressive work! I especially like your method for making the buttons. I struggled with a good technique and what I came up with worked, it just took a long time to assemble them. I may need to convert to your way! :D

Outstanding work Warhog. Thanks for sharing your techniques. Really appreciated :thumbup:

Cheers

Hans

Really nice work John

Cheers

Peter

John, good that you decided to post your work here as well. very interesting solution with sandwiched PCBs.

Thanks for posting. I'm trying to start work on my CDU buttons and this has given me lots of new ideas to try!

Thank you, Warhog. Very informative and a lot of good ideas :)

Very impressive. As I don't speak fluently english, I could not fully understand how you made the buttons and the engraving. Any chance to explain again with some more dedicated pictures?

Your work on the panels shows talent ,that's for sure

Exceptional talent!

:thumbup:

Randy

Very nice work. Thanks for sharing!

Great tutorial! Thanks, John

Great Job Warhog! Please tell me what kind of mill you are using.

Thanks

Hi Clay

I use a TAIG CNC mill from the US.:thumbup: Its table size is just large enough to do all but maybe 4 panels. For those panels its just a matter of cutting the top half first, flip the work piece and do the bottom half next. All things considered its a bit of a hassle but the cure is rather expensive..ie new larger mill.:(

This is my baby....

Unfortunately there are very few accurate, reasonably priced CNC mills to choose from in a size that would suit our needs without you having to sell your kid or wife to pay for it. Yes there are the cheap chinese things but they lack any amount of accuracy to do ALL that's needed in building a cockpit. Its really to bad because some of them look SO NICE its hard to believe they are so problematic. But that how they suck you in.

Hi Warhog

How did you do the Buttons?

Cheers Evilfisher

There is a description in the very first post that lists all the steps required to make a button including backlighting the button.

There is a description in the very first post that lists all the steps required to make a button including backlighting the button.

Thank you very much for your reply, problem is i dont get it.

You are refering to :

The push buttons themselves are made from white styrene plastic, around .3" thick. The plastic is first painted and then engraved. Then the whole thing is flipped upside down and hollowed out with the mill. I do this to ensure good light penetration to the underside of the engraved button top. Each push button has a clear cube of acrylic placed inside it to act as the bottom of the button so it will make contact with the tactile switch post. I could have used a solid acrylic button instead of all this hollowing out business and then adding some acrylic cube to it... bit I like the feel of styrene buttons. Acrylic buttons just feel to hard.

Sorry maybe its because english isnt my native language

but the only thing i can made out of it is:

"The push buttons themselves are made from white styrene plastic, around .3 thick"

that gives me no indicator if its a block styrene that you cut out or if its molded etc...

I hope you can understand me

Cheers Evilfisher

Freaking Awesome Work!! Thanks for sharing.

I would love to have the room to get a CNC mill like that. Currently, I have to use CNC milling services, which gets expensive very fast.

Fantastic post, John! You're incredible, really! I need to send you an email, so keep a look out.

The buttons are cut from a sheet of styrene. The sheet is around 2”x3”. I normally cut 20 or so buttons at a time. I haven't been able to source styrene sheet in that thickness so i had to improvise. I glue thinner sheets together until I have the desired thickness. The glue used for styrene bonds the thinner sheets together into one solid, thick styrene sheet.

The sheet of styrene is painted with grey acrylic paint. Once the paint has dried, I engrave the tops of the buttons. The sheet is flipped upside down and the mill hollows out each button. It’s then flipped over again and the mill cuts out each button. The styrene sheet has to be registered each time it’s flipped so the mill only cuts where it’s supposed to cut.

Hope that helps.