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'LCD projects'
1998\07\23@212748 by Timothy D. Gray

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Has anyone sucessfully backlit a non-backlight LCD display? or anyone have
a source for backlit 16X1 lcd's? My current PIC project is a automotive
heater control system, I've got the basics done except for getting a red
backlight. everything on the market is green or blue.

1998\07\24@025539 by

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Unfortunately it's not generaly possible.  The non-backlit displays use a
fully reflective material at the rear of the glass, the backlit type use a
semi reflective material that allows light to pass through it from the rear.
It tried this when I had a couple of 16 x 2 displays one backlit, one not.
The screen in the backlit one was cracked, so I took 'em both apart and
swapped the display from the non-backlit one.  I may just as well not
bothered, I couldn't see any light comming through the display.

Maybe some of the non-backlit displays use the semi-reflective material, but
I wouldn't bank on it.

Mike Rigby-Jones
spam_OUTmrjonesTakeThisOuTspamnortel.co.uk


> Has anyone sucessfully backlit a non-backlight LCD display? or anyone have
> a source for backlit 16X1 lcd's? My current PIC project is a automotive
> heater control system, I've got the basics done except for getting a red
> backlight. everything on the market is green or blue.
>

1998\07\24@072354 by Mark Willis

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Timothy D. Gray wrote:
>
> Has anyone sucessfully backlit a non-backlight LCD display? or anyone have
> a source for backlit 16X1 lcd's? My current PIC project is a automotive
> heater control system, I've got the basics done except for getting a red
> backlight. everything on the market is green or blue.

 Possibly, use those high-powered LED's (Radio Shack carries these,
among other sources) as front lighting?  Those are pretty darn bright,
if you aimed them at a diffuser or a curved mirror that might do the
trick...  I've thought of building a few of those into a red automotive
instrument lighting system like aircraft use (no night blindness
problems, and you can make it pretty bright!) for one car that likes to
eat instrument light bulbs & is a horror to replace bulbs on...

 Maybe edge-lighting is possible, also?

 Mark Willis, .....mwillisKILLspamspam@spam@nwlink.com

1998\07\24@073353 by Coetzee, Morne

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Try using edge lighting LED modules. I think they're available in
different colors.
You just mount them on both sides of your display.

MornŽ Coetzee

> {Original Message removed}

1998\07\24@084026 by Peter L. Peres

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On Fri, 24 Jul 1998, Rigby-Jones, Michael [PAI01:4837:EXCH] wrote:

> Unfortunately it's not generaly possible.  The non-backlit displays use a
> fully reflective material at the rear of the glass, the backlit type use a
> semi reflective material that allows light to pass through it from the rear.
> It tried this when I had a couple of 16 x 2 displays one backlit, one not.
> The screen in the backlit one was cracked, so I took 'em both apart and
> swapped the display from the non-backlit one.  I may just as well not
> bothered, I couldn't see any light comming through the display.
>
> Maybe some of the non-backlit displays use the semi-reflective material, but
> I wouldn't bank on it.

Imho you could try to peel off the mirror layer and paste a piece of mylar
foil (f.ex. from a thermal survival blanket of the kind sold in travel
shops), using a transparent paper glue. This does what you need
(semi-transparent and reflective).

In fact, many non-backlit panels can be... side-lit ! There are hollows in
the bezel meant for small bulbs. This is what I had in mind with my
previous posting.

There is also the option of projection lighting. For this, place 3-10
bright LEDs in a can and arrange it on the ceiling or in front of and
below the dash to shine onto the dash where required (works best for the
middle console).

Last, knowing that older aircraft used an UV 'black light' lamp to make
the markings on instruments shine in the drak, it should be possible to
replace the mirror behind the LCD with a strip of fluorescent tape (same
supply as thermal blanket) and see what can be done with an EPROM eraser
light for starters (do yourself a favor and wear goggles and remove your
bare skin from the light as much as possible - UV-C light is not good for
people).  It may be necessary to illuminate the LCD from the back.

Peter

1998\07\24@084035 by Peter L. Peres

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On Thu, 23 Jul 1998, Timothy D. Gray wrote:

> Has anyone sucessfully backlit a non-backlight LCD display? or anyone have
> a source for backlit 16X1 lcd's? My current PIC project is a automotive
> heater control system, I've got the basics done except for getting a red
> backlight. everything on the market is green or blue.

That's because everyone uses FL or EL backlights or evel LEDs. I guess you
are trying to use LEDs. If this is homebrew, go out and buy a bunch of
small HV signal lamps (argon + Hg = white coating, green light). Connect
these in series with 0.1 uF/250 V each into the secondary of a small
upconverter using a ferrite transformer and drive from an astable or
IRF??? + PIC output at ~= 10 kHz. I've used the transformer from a small
mains DC/DC power supply for this with success. You can hang up to 20
lamps on the secondary w/o problems, but use shielded cable rated 220 Vac
or more. The intensity can be varied by changing the duty cycle. 50% is
max, then 40%, 20%, and off.

For production, there are neat little lamps for this, and you can order
transformers amde to order. For reasons I do not care to explain here,
this is never used in radios and audio equipment ;)

Peter

1998\07\24@112340 by Alan King

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I've never seen a red one mentioned in a data book.  But
that's probably due to eye response, if you're gonna give up
1/2 amp for backlighting may as well get the brightest
visual which is green generally.  Course in a car (or plane)
at night red affects night vision a lot less..  Anyway,
first thought is to take a green led backlight display apart
and see what's going on.  I haven't done this but always
assumed they're using surface mount LEDs for space
reasons..  For small numbers of displays and definitely for
testing purposes change one over manually to red.  Sounds
neat enough I may do one myself.  Electronic Goldmine is an
easy/cheap place to get the LEDs.  If you needed medium
quantities get in touch with a manufacturer and they could
probably do them for you.  In fact I bet if you look for
aircraft oriented stuff you could find some made red already
due to the night vision problems created by other colors..
Alan

1998\07\24@150038 by Timothy D. Gray

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I tried a test with edge lighting and it didn't seem to get any decent
results. I was wondering if anyone has a source for these edge modules, as
discreet led's dont work well (I used 6 super brights, the light just wont
bend to reflect off the rear)

On Fri, 24 Jul 1998, Coetzee, Morne wrote:

> Try using edge lighting LED modules. I think they're available in
> different colors.
> You just mount them on both sides of your display.
>
> Morné Coetzee
>
> > {Original Message removed}

1998\07\24@160031 by Timothy D. Gray

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Actually most aircraft displays are now a Green/blue mixture to meet with
what the govt. uses in it's fighters. This (teal) color seems to have the
same effect as red lighting except the wavelength of the color must not
vary more than 2% or the pilots vision will be affected. (Oh wonderful
have a service company replace all the color filters in the aircraft every
2 years, corperate america is great aint it?) Red does not suffer from
this intolerance to color shift. My reason for using red is mostly vain,
all my gagues are red backlit, so I wanted it to look the same. :-) it
seems that the best results are from a row of led's along the top edge
shining into the display works best.. I finally found an edge lit display
and they have a plastic white reflector on the rear to evenly disperse
the
light.

On Fri, 24 Jul 1998, Alan King wrote:

{Quote hidden}

1998\07\24@161902 by paulb

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Timothy D. Gray wrote:

> I was wondering if anyone has a source for these edge modules, as
> discreet led's dont work well (I used 6 super brights, the light just
> wont bend to reflect off the rear)

 You were using SMD LEDs of course?  Not 5mm ones?

 Just asking.  I cobbled one to my (wife's) bedside clock to edge-
illuminate the tuner display.  (Bulb kept burning out!).  Not too
effective, but I cut the LED short to get the very chip near the edge.
You want almost a bare die - SMD would be the closest.
--
 Cheers,
       Paul B.

1998\07\24@164531 by Timothy D. Gray

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Actually I ground off the faces of the 5mm led's to get the chip as close
as possible to the glass edge.

On Sat, 25 Jul 1998, Paul B. Webster VK2BZC wrote:

{Quote hidden}

1998\07\24@172857 by Mark Willis

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Peter L. Peres wrote:
{Quote hidden}

 Please, NO!

 Please use the black light style they use to light the '60s
psychedelic posters, instead.  Or perhaps a bug-attracting lamp,
instead.  (I'll ship mine to you if you want, instead of seeing someone
give themselves skin cancer in a week or two of use.)  UV-A or UV-B or
whatever those are.  Anything, instead.

 You REALLY don't want to be bathed in UV-C from an EPRom eraser or a
germicidal lamp, for hours on end.  Especially when there are so much
better solutions, like the safe UV bands, red incandescent remote
lighting, edge lighting, or those high-output LEDs.  (If you want to
hurt yourself, please do it some simpler way!)  Cataracts are not MY
idea of a safe result from instrument lighting, folks!

 Let's NOT do that, and say we didn't.  PLEASE.

 Could use the edge lighting bulb holes (if present) for high-output
Red LED's, that would give him the red panel illumination he wanted.

 Mark Willis, mwillisspamKILLspamnwlink.com

1998\07\24@182942 by Peter L. Peres

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On Fri, 24 Jul 1998, Mark Willis wrote:

Ho ! I said use the EPROM light for testing only, with precautions, in the
lab or whatever. Then of course one would switch to a black light lamp
(it's called UV-A btw).

I said it's dangerous and to take precautions, but I suspect that walking
in the sun for 8 hours now is FAR worse, not just for UV reasons.

Of course, if you have a black light lamp, *strongly* prefer it over the
EPROM light solution. The original instrument lights appeared to use a red
lamp AND a UV-A lamp, exactly like the bug-killer lamps. The red light
illuminated the dash etc and the black light gave contrast on the markings
and needles. Each had its own switch.

>   Let's NOT do that, and say we didn't.  PLEASE.
>
>   Could use the edge lighting bulb holes (if present) for high-output
> Red LED's, that would give him the red panel illumination he wanted.
>
>   Mark Willis, .....mwillisKILLspamspam.....nwlink.com

Peter

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