TI-H: Re: Backlight: How to build!

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TI-H: Re: Backlight: How to build!

I did some expirimenting. If you go to a local hardware store such as 
Ace Hardware, you can get plexiglass. Ask for small scraps and find a 
piece that will cover the screen nice. You may want them to cut it for 
you, so you get a good edge.

Use sand paper and scratch one side perpendicular to the LED source. 
THis will reflect the light up. The mirror needs to be placed on the 
back of the Plexiglass and the plexiglass then against the back of the 
LCD.

The LCD will be tight, and it may be necesary to NOT TIGHTEN the two LCD 
screen screws all the way. Remember that the back of the case pushes the 
screen too. You will also need to remove the foam from the inside of the 
back cover to make room.

As for the LEDs, I used 6 hight brightness Yellow LEDs for mine. The 
greens probably would have been better, but they didn't come bright 
enough. I put them in groups of two in parralel, with alternating serial 
connections like this...

                               \
   ---------   ------\/\/\---o  \o___
   | |   | |   | |
   v v   ^ ^   v v
   | |   | |   | |
------   ---------

I expirimented with values, but forgot what was best. You could also 
replace the resistor with a variable resistor to adjust for just 
slightly dim or totaly dark conditions.

I will also warn again about being careful with those plastic wire 
ribbons on the LCD. THEY CAN NOT BE FIXED!!! Also, don't crack your LCD. 
Try to get EXTRA thin plexiglass. 2 mm thickness is about the MAXIMUM!
>
>How do I get/build the Diffuser?
>
>Gregory Whitmore wrote:
>
>> When you peel off that gray "mirror" from your LCD and compare it to 
the EL
>> panel that I use. You can't tell a difference. When it is off, 
everything looks
>> like a stock calculator. When the unit is on, it looks like an 
indiglo watch.
>> You just have to adjust the contrast a little to make up for the 
extra light.
>> It actually looks damn good.
>>
>> Richard Piotter wrote:
>>
>> >  it's not better, in my own opinion, if you HAVE to have it plugged 
into
>> > an external supply to run it. My option costs only $40 (maybe 
less), and
>> > it lights the entire screen nicely. You will STILL have the SAME 
PROBLEM
>> > with the DIMMER pixels and DARKER background. It has to do with the
>> > polarizer. I hope you figure it out, but as long as mine works, 
it's
>> > fine. I will have to use a different brand or model screen, cause 
these
>> > are nolonger sold, but many monochrome displays use this setup to 
light
>> > up, so I just need to look!
>> >
>> > >
>> > >I have found a better way to do the backlight. The only problem is 
it
>> > >costs $95.00 and it HAS to have an external power supply. It has 
to
>> > >because it needs an inverter to use DC power. I forget the name of 
the
>> > >company right now, when I remember I will post. To install the 
thing is
>> > >really simple though. You just pull the gray "mirror" from your 
screen
>> > >and put place this screen behind your LCD. It sticks using that 
static
>> > >kinda thing.
>> > >
>> > >Gregory
>> > >
>> > >
>> > >
>> > >
>> > >Richard Piotter wrote:
>> > >>
>> > >> Hi!
>> > >>
>> > >> I want to post it, but time and work have prevented me from even
>> > >> updating the battery expander page. I took a Sharp LM64P 
something
>> > >> backlit monochrome LCD apart. It is 640x480 pixsels, and the
>> > >> diffratction panel is really good. Lights the whole screen if 
cut
>> > right!
>> > >> I don't guarantee your screen will work WELL with it, but I do
>> > guarantee
>> > >> it will light it up. The screen lights fine. The problem comes 
in
>> > with
>> > >> some newer screens (maybe it's newer screens, but I'm not sure). 
The
>> > >> problem is that to properly install the backlight, you need to 
cut
>> > the
>> > >> rubber that holds the screen off and then peel the mirror off. 
You
>> > put
>> > >> the mirror on the back (rough) side of the difractor and put a
>> > diffuser
>> > >> on top, then the LCD. The problem is that some screens use the 
mirror
>> > >> and polarizer at a different angle, and it isn't compatible with 
the
>> > >> diffuser. It dimms the pixels and darkens the background. It 
isn't
>> > bad
>> > >> on some calcs, but it gets fairly annoying on others. Austin 
butler
>> > had
>> > >> a "dim" calc, but he got it and said it took a while to get used 
to,
>> > but
>> > >> that it wasn't too bad. All I can say is you can try. The 
problem is
>> > it
>> > >> it is a dim one and you decide not to do it, it is nearly 
impossible
>> > to
>> > >> put the mirror back on without looking VERY strange. It will 
have air
>> > >> bubles and dust, no mater how you replace it. If you like you 
can try
>> > >> with just the corner, but my experience shows that if the mirror 
is a
>> > >> piece of thick plastic and the one that doesn't work as well (It
>> > works,
>> > >> just dimmer pixels when the light is off) is a very flexible 
piece of
>> > >> plastic foil. You'll know by pulling the corner off. If it is 
thick,
>> > go
>> > >> for it. if it is thin, you may want to think about it. Try it if 
you
>> > get
>> > >> a panel. I charge $40 for the whole job (it has to cover the 
cost of
>> > the
>> > >> LCD panel I took apart). I got it from ALL electronics, but they
>> > >> nolonger sell it, so it is kindof my last priority. I have 
enough for
>> > 4
>> > >> calcs, and will need 2 or three for myself, so you, austin, and 
I
>> > could
>> > >> end up being the only person with these backlights unless 
someone had
>> > >> the misfortune of ordering the wrong LCD or thinking they could 
use
>> > it,
>> > >> but couldn't. I was on an LCD list before, so maybe I can 
purchase
>> > some.
>> > >> It would be best to find a black ON white backlit screen. It 
would
>> > look
>> > >> better, but I havn't found one yet.
>> > >>
>> > >> If you want it done, I can do it for you. I could send the piece 
(fit
>> > it
>> > >> to my 82 first) but It is difficult and requires patience. I 
have
>> > taken
>> > >> over half an hour just cutting the screen off, cause you 
obviously
>> > can't
>> > >> crack it, and you can't cut those plastic ribbon wires. Tell me 
what
>> > you
>> > >> want to do. I'll do my TI-82 before I do your TI-82, just to see 
if
>> > it
>> > >> works well!
>> > >>
>> > >> Respond soon!
>> > >>
>> > >> Richard Piotter
>> > >>
>> > >> E-Mail:
>> > >> richfiles1@hotmail.com
>> > >> richfiles@usa.net
>> > >>
>> > >> The Richfiles:
>> > >> <A
>> > >>
>> > 
HREF="http://www.geocities.com/SiliconValley/Lakes/5081/Richfiles.html">The
>> > >> Richfiles TI Page</A>
>> > >> <A
>> > HREF="http://www.geocities.com/Area51/Lair/8510/Richfiles.html">The
>> > >> Richfiles Model Building Page</A>
>> > >>
>> > >> ______________________________________________________
>> > >> Get Your Private, Free Email at http://www.hotmail.com
>> > >
>> >
>> > ______________________________________________________
>> > Get Your Private, Free Email at http://www.hotmail.com
>
>
>
>


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