How to make backlit buttons and annunciators?

[xray20]

Now I have LEDs working through Arduino and DCS-BIOS, I want to make some backlit annunciators like 'Take-off Trim' and 'Nosewheel steering' etc.

I have had a look through the forum and can't find much detail.

 

How are you building these annunciators? Specifically how do you make the transparent lettering with the dark background?

 

Cheers

Matt

[Warhog]

You take a piece of clear acrylic and paint it black on the inside surface. Then you can engrave the lettering on the inside cutting through the black paint. The lettering, of course, has to be a mirror image of what you want to show in the front or outside view of the indicator. Last thing is to paint the inside housing black. Always use FLAT black for these type of components so you minimize any reflections.

 

With no lighting on you can barely make out any lettering and with the lighting on you get...

 

 

 

 

If you wish to remove any sign of lettering whatsoever you need to add a piece of smoked acrylic and place it at the very front of the indicator.

 

Also make sure to attend to any light leaks which has not yet been done in the pic above. They really detract from the overal affect.

[xray20]

Thanks John,

So no way to do this without an engraver?

This looks like an expensive proposition. I have just had a look on Ebay and suitable machines look like they are going for many hundreds of pounds.

What do you use?

[agrasyuk]

The other way would be to mask the lettering , paint and then remove the mask. Maybe use some set of letter decals for plastic modelling as masks. But even then it will be a very demanding task . practically I don't see a very good way to accomplish this without engraver of sorts.

 

I will offer this picture.

White plastic painted black and engraved on the top (not mirror). On the top a piece of green transparent acryl is glued serving as filter. Two styrene strips glued on each side shielding from cross light bleed and shadowing the engraved text.

 

Edited December 20, 2015 by agrasyuk

[cichlidfan]

I have never tried it, but it might be worth the experiment.

 

Using a hand held electric engraver, with an engraving template. The button and the template would have to be held very securely, which means setting up for each letter would be time consuming, in order to be accurately placed. Also, I have no doubt that the edges will be far less smooth.

 

EDIT: This was just a passing thought, since I was just using such an engraving tool.

[xray20]

Photo Etch?

 

OK, I'm going to try something here. I think it may be possible to make these using a photo etch technique.

I think it will be possible to make masks using photoshop or similar print them on Inkjet acetate and etch thin brass sheet. It will be necessary to make webs on letters like O and P like a stencil so the centres don't drop out.

 

Have a look at this....

I have just ordered some photo resist spray called POSITIV 20 available in the UK from Farnell

for £10.

 

http://uk.farnell.com/kontakt-chemie/positiv-20-200ml/positive-resist-positiv-20-200ml/dp/801010

 

The developer and etcher are available from local electronics stores (Maplin) and are the same as used for PCB manufacture.

0.1mm brass sheet is available from EBay.

 

I'll let you know how I get on

Matt

[cichlidfan]

I though about photo etching but I wasn't sure what materials it would work with. I only think of it for metal etching, i.e. circuit boards.

[xray20]

I though about photo etching but I wasn't sure what materials it would work with. I only think of it for metal etching, i.e. circuit boards.

 

Yes, I want to use metal sheet. Its perfectly opaque so it can be really thin (< 0.1mm)

It's the same thing. Circuit board is only metal film stuck to a board. It etches through perfectly.

I think the acid etcher (Ferric Chloride or something less nasty) will cut through copper, brass or steel.

 

I'm thinking about how to mount the etched masks in the bezels now. Maybe clear epoxy resin?

[Mr_Burns]

You know if you use warhogs idea, it might be easy to remove the paint using say a ballpoint pen with the ball removed (or one without ink and with the ball?) and a plastic stencil of the Alphabet.

 

So spray green translucent sheet black, get one of those letter stencils and scratch the paint off.

 

Finish would have a different font but it could be a very simple solution that might meet your needs?

 

When done cut to the size you need and slick it face down, not sure what type of paint to suggest?

[Warhog]

Why not print it on an acetate sheet? The clear sheets they used with overhead projectors many years ago. That could work.

 

John

[Deadman]

It has been tried and does not work. I can't recall the members name he made printed left and right consoles he reported it failed later.

I tried the same repeated printing on film it does not block all of the light.I would suggest purchasing annunciators off of ebay replace the old lens with a green blue shade of glass or acrylic and silk screen the ledged.

[BravoYankee4]

Here is another way of doing it :)

 

Also note the mechanical dimmer.

[xray20]

Here is another way of doing it :)

 

Very Nice. But the problem with A-10 annunciators is that the letters are lit on a black background. The inverse of this set-up.

The layered construction is something I will follow though.

[BravoYankee4]

Very Nice. But the problem with A-10 annunciators is that the letters are lit on a black background. The inverse of this set-up.

The layered construction is something I will follow though.

 

Well, just print the label film inverted :thumbup:

A standard laser printer with OH-film would do that. Even better would be to do it with a stencil cutter and black vinyl of course.

[Warhog]

This is an interesting technique.

 

http://mazda626.net/topic/39309-making-custom-gauge-faces/

[Kubi]

I used self adhesive transparent sheet for Ink Printer.

I put 4 layers together. Looks good for me.

 

http://forums.eagle.ru/showpost.php?p=1712123&postcount=23

[xray20]

I used self adhesive transparent sheet for Ink Printer.

I put 4 layers together. Looks good for me.

Nice job. I would be happy with that.

I have ordered all of my parts. Acetate, 0.1mm brass sheet, photosensitive film, photosensitive aerosol. Hopefully it will arrive before Christmas. I'll report on my progress.

[xray20]

I have just tested with printing on inkjet acetate and (just as Warhog said) the ink is just not dense enough.

I tried two passes, loading up the acetate with as much ink as it could handle without running and its better but still not good enough. The brass sheet arrived today. If I can get some sodium hydroxide on Christmas Eve I'll try etching.

I wonder if the problems with ink density will also apply when I'm trying to expose the photosensitive film.

 

BTW I found some aluminium channel at my local hardware shop (B&Q). I glued two pieces together to make a box. Its about the right size for the annunciator frame. Better than any box section aluminium I've been able to find.

 

Happy Christmas

Matt

[Mr_Burns]

Did you try printing four of them and sticking them on top of each other as suggested above?

 

Like the aluminium idea btw - pinched!

[jrsteensen]

From experimental a bunch of years ago, I found doing four layers laser printed to be optimal with this method, with a 1/16 sheet of smoked acrylic over top to eliminate the visibility of the characters when not lit.

[xray20]

My experiments with acid etching have not been successful so far.

The problem with the inkjet printed transparency not being sufficiently opaque to be an original label is the same problem when trying to expose photo-resist. The UV light bleeds through the black bits and partially exposes the photo-resist, so it won't develop properly. I'll try with some different timings and see if its any better, but I fear this approach is a dead end.

 

Meanwhile my wife is not talking to me as I spilled ferric chloride in the Christmas gravy.

:pain:

[agrasyuk]

For etching solution I suggest you try hydrochloric acid/ox peroxide solution. Much more friendly then the ferric stuff.

For masking see if toner transfer will work better , no laminating photoresists, no uv exposure required.

[hansangb]

I'm curious. Do folks use clear acrylic or "matte" ones (little cloudy)?

 

In this example http://forums.eagle.ru/showpost.php?p=1712123&postcount=23, it looks like the acrylic is *not* clear - which may actually help with light leakage?

 

thanks

[Kubi]

I have used clear sheets. But as I had mentioned in my example, it works quite well.

[hansangb]

Thanks Kubi. I'll order some now!