# LCD (Liquid Crystal Display) IO

Manufactures use the term Vcc-Vee to describe the LCD bias voltage. This is actually a NEGATIVE voltage! For example, from the Optrex DMF5005 data sheet: Supply Voltage (LCD Drive) Vcc-Vee is Min=8V Max=26V. Do the algebra: If Vcc=5v, for the Minimum value, Vcc-Vee=8, 5-Vee=8, 5=8+Vee, -3=Vee. The max is -21 volts.

A lot of LCD panels (with a built in controller) need up to 50ms after power up before they can accept commands. Check the data sheet.

A well written response to a question of directly driving LCDs from microcontrollers:

The truth is, I suspect, that most of us haven't a clue about how to drive LCDs from a micro, because the LCD display market is totally owned by the Far Eastern consumer electronics majors and for most Western  engineers the only available course of action is to buy one together with its fabulously specialised driver chips, and follow the instructions. This is not, of course, calculated to produce lowest-cost, lowest component count solutions. Not that there's any protectionism in the Pacific Rim electronics industry, of course (;->)

Driving LCDs with only a few segments is easy: you apply a square wave to one face of the LCD (the "backplane") and apply to each segment electrode either the same square wave (segment off) or the anti-phase square wave (segment on). Many micros designed for consumer and instrumentation applications have built-in LCD drivers for exactly this purpose. But clearly it requires N+1 wires to support N segments. Fine for the display on a multimeter or a central heating programmer, but hopeless for graphics. [ed: see:

High segment count (i.e. graphic) LCDs use a much more elaborate multiplexing scheme which in practice demands a custom chip for each family of displays. Doing it from scratch is a major project and you would probably have very great difficulty getting enough info on the raw LCD to be able to do it. You are more-or-less cornered into buying the LCD together with its driver.

And that means that you have to be in with a chance of understanding the data sheet. This probably requires not only a modest amount of experience of microcontroller projects, but also some parapsychic expertise to cope with the translation into English from Korean, Japanese, Yogistani or whatever. I think you need to find a soul-mate who's done something similar before.

Sorry to be so negative and depressing. Jonathan Bromley

If you are driving the pixels directly with DC you will destroy the LCD. You need to drive them with a perfect square wave 180 degrees out of phase so that the LCD sees an alternating polarity. Why? Because liquid crystal is a chemical that will electrolyze into its components just like water will go to hydrogen and oxygen, or other items will "plate out" components onto one electrode or the other. This destroys the ability of the "liquid crystal" to react.

LCD displays, particularly the serial input type, already have the appropriate drivers in the hardware and they are transparent to the user.

Rather than use EL or other expensive backlighting panels:

Try frosting one side of a piece of plexiglass, putting LEDs (especially Blue) around the edge, and the panel in front. If you have access to someone who can plate or vapor deposit a metal film on the frosted back, even better.

Not as great as a panel, but the frosting will cause the edge lighting to bounce around a lot and come out the front more or less uniformly. Cheap, and it does work. Made a lot of edge lighted signs (Exit etc.) using plexiglass and a router years ago. Light would hit the routed letters and make them glow with a nice blue-green. Really pretty.

Jinx says:

I've been trying the Varitronix MGLS160128 graphics unit as a replacement for an older green screen. The contrast on this new type is quite a marked improvement on even the standard black/ silver screens. It is almost black on white. The only snag so far is that the standard screen could be run fairly simply on batteries, using 7660 inverters to get the -15V supply. The MGLS160128 is quite demanding, requiring +5, -21 and -13.7 for best performance

See also:

## manufacturers

LCD manufacturers

## Surplus LCD suppliers

Questions:

• SPAMluke.bacewicz~NOSPAM~ at SPAMgmail.com asks:
I am having a difficult time tracking down manufacturers who offer full display screens 2x2 or 2x2.5". I want to fabricate a small tv set (think dollhouse)for a college project. Hope to display video of green energy and conservation in a fellow students architecture project. Does this have any feasibility or should I just stuff a zune or ipod in a teeny wall mount display?

James Newton replies: Jameco has a 4" unit, and I've seen a smaller one, but have no idea where to find them.+

+

• SPAMisdn128~NOSPAM~ at SPAMbellsouth.net asks:
http://www.gpscruise.com I have an LCD like you have (2line cheapo, but cool)

Q: How to hack the LCD so that
----I can see the LCD in the dark???--------

(I currently have a flashlight pointing at it, but thats lame)

James Newton replies: I would suggest white or other super bright LEDs shining from the side. You may have to remove part of the panel frame or perhaps bend the LED so it shines from just above the frame back onto the LCD. Congratulations on GPSCruise!+

+

• hi I want to know what type of LCD used in automotive.that is used cases of LCD in Cars etc. James Newton replies: The same type you use everywhere else.+

+

• SPAMnari_marotu~NOSPAM~ at SPAMyahoo.co.in asks: " hi i want the data sheet of LM16213 LCD could you please suggest the web site where i can get that" James Newton replies: Your best bet is to contact lampex.com and see if they have fixed their user registration system so that you can download it from them. If they are still not up, email them at SPAMsales~NOSPAM~ at SPAMlampex.com and ask them to send it to you or fix their web site.+

+

• SPAMkvn_ouma~NOSPAM~ at SPAMyahoo.com asks:
Hi.

Thanks for all your info. Mine is a very simple question: I would simply like to make any bright phone LCD to light as part of my college project. I don't want to design any fancy displays, just to make an LCD light on and off.

Could anybody out there kindly help with ideas?

Thanks a million.

Kevin Taka.

James Newton replies: See electroluminescent or LED back lighting.+

+

• Bambang Sunjoto asks: "Hi, I had problem using Topway LMB162ABC (made in china), they say its Hitachi 44780 compatible. Anyone had any experience with it ?"
• SPAMatl_trota_mundo~NOSPAM~ at SPAMyahoo.com.mx asks: " hi!... i'm lookin information about lcd AA76020C from panasonic tx310 cell, if anybody has any information, i apreciate.!!!

" +
• marcelo_ga(at)hotmail.com asks:
hello,
I would like to know if you have, or know where to find, the data sheet of an RCL Display: DC12300 (found on an Ericsson CF388 cellphone). Thank you in advance.
• SPAMajit_motra~NOSPAM~ at SPAMst.com asks:
hi,
i want nokia's lcd pin configuration. I want to make
a small project to display images on nokia's lcd which is easily available
in market. Can anyone help me.
regards -ajit

James Newton replies: http://sandiding.tripod.com/lcd.html Has all the information you need. By the way did you know how Nokia got that name? Its the sound made by the siamese twin elephants (joined at the trunk) whenever they tried to trumpet. +

• Yair Ben Ari asks:
hi, I am writing function on the T6963C to write fonts with something like 9x16 size (the point is that it should be bigger then the original fonts that comes with the LCD.) but there is a problem the display process takes a lot of time, is there a way to write a double buffer or something like that to nake this process faster? Yair

+

Archive:

 file: /Techref/lcds.htm, 20KB, , updated: 2017/4/14 07:30, local time: 2024/4/20 04:27, TOP NEW HELP FIND:  3.230.143.213:LOG IN

 ©2024 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions?Please DO link to this page! Digg it! / MAKE! HD44780,T6963 LCD, KS0108 LCD, Liquid Crystal Display

After you find an appropriate page, you are invited to your to this massmind site! (posts will be visible only to you before review) Just type a nice message (short messages are blocked as spam) in the box and press the Post button. (HTML welcomed, but not the <A tag: Instead, use the link box to link to another page. A tutorial is available Members can login to post directly, become page editors, and be credited for their posts.

Link? Put it here:
if you want a response, please enter your email address:
Attn spammers: All posts are reviewed before being made visible to anyone other than the poster.
 Did you find what you needed? "No. I'm looking for: " "No. Take me to the search page." "No. Take me to the top so I can drill down by catagory" "No. I'm willing to pay for help, please refer me to a qualified consultant"

.