LCD! How do I use them?

[P6Mole]

What I want to do is to create a module that I can display 4 lines of numbers.
1) Water temp,
2) Oil pressure,
3) Fuel level,
4) Time.
all for a car.

I understand that You can buy kits but they cost hundres. I want to build it
myself.
Its the control of the LCD I know nothing about.

Can you help?

 

[happyhobit]

Well that would depend on what you do know. Do you know electronics and
microcontrollers?

Jay

 

[Tom Bruhns]

What I want to do is to create a module that I can display 4 lines of numbers.
1) Water temp,
2) Oil pressure,
3) Fuel level,
4) Time.
all for a car.

I understand that You can buy kits but they cost hundres. I want to build it
myself.
Its the control of the LCD I know nothing about.

You can buy little alphanumeric LCD modules (or vacuum fluorescent
ones that might be easier to read under various lighting conditions).
You can find documentation on how to interface to them on the web,
though what I've seen tends toward the sketchy side. I have a data
book I've annotated that I use. Almost all of them use the same
scheme; you have a simple interface of three control lines and four or
eight data lines. You end up telling it a starting point and then
sending it the ASCII data to display. The most reasonable way to do
that is usually through an inexpensive processor. You can find
example code on the Microchip web site for PIC processors, though if
they haven't ever gotten around to updating the application note,
there's an error in the code that might cause you some headaches.
Presumably you'll be able to figure out how to get numerical
representations of the things you want to display. You'll find that
the displays when new in small quantity are a bit pricey, and you may
decide to use fewer lines of display with a way to select what you
display.

Cheers,
Tom

 

[Rich Webb]

What I want to do is to create a module that I can display 4 lines of numbers.
1) Water temp,
2) Oil pressure,
3) Fuel level,
4) Time.
all for a car.

I understand that You can buy kits but they cost hundres. I want to build it
myself.
Its the control of the LCD I know nothing about.

If it's a "typical" 4x16 or 4x20 LCD display then the manual at
http://www.optrex.com/pdfs/Dmcman_full.pdf should have all the
information that you'll need to know.

If you search around, you can often find surplus/overstock/odd lot LCDs
at very reasonable prices. Try (among many others)
www.allelectronics.com
www.mpja.com
www.bgmicro.com

You'll probably want a backlit display. LED backlights are easier to
interface to although typically not as even an illumination as the
EL backlights.

 

[David Russell]

Go to www.digikey.com and look at LCD display modules. The cost of a raw
LCD + a controller is about the same as one of these modules WITH
controller. Either way, however, you are looking at about a hundred bucks
in low quantities. I know that's not what you asked, but if the difference
is as small as I think it is, you're not saving enough to make up for the
pain of doing all of the controller yourself. But if you're determined, get
the data sheets and application notes for one of the raw display at digikey
and get whatever embedded processor you're using to do all the work.

Hope that helps
daver

 

[Jacobe Hazzard]

What I want to do is to create a module that I can display 4 lines of
numbers. 1) Water temp,
2) Oil pressure,
3) Fuel level,
4) Time.
all for a car.

I understand that You can buy kits but they cost hundres. I want to
build it myself.
Its the control of the LCD I know nothing about.

Can you help?

http://www.allelectronics.com/cgi-bin/category.cgi?category=search&item=LCD-87&type=store

$11 for a four-line LCD with a link to the datasheet.

Adam

 

[Active8]

Go to www.digikey.com and look at LCD display modules. The cost of a raw
LCD + a controller is about the same as one of these modules WITH
controller. Either way, however, you are looking at about a hundred bucks
in low quantities. I know that's not what you asked, but if the difference
is as small as I think it is, you're not saving enough to make up for the
pain of doing all of the controller yourself. But if you're determined, get
the data sheets and application notes for one of the raw display at digikey
and get whatever embedded processor you're using to do all the work.

Hope that helps
daver

don't scare the guy. 20x4 LCD modules with controllers can be puchased
for $8 - $20. where this $100 come from, Hosfelt?

mike

 

[Roy J. Tellason]

If it's a "typical" 4x16 or 4x20 LCD display then the manual at
http://www.optrex.com/pdfs/Dmcman_full.pdf should have all the
information that you'll need to know.

If you search around, you can often find surplus/overstock/odd lot LCDs
at very reasonable prices. Try (among many others)
www.allelectronics.com
www.mpja.com
www.bgmicro.com

You'll probably want a backlit display. LED backlights are easier to
interface to although typically not as even an illumination as the
EL backlights.

Speaking of which...

I scrounge a lot of parts, scrapping all sorts of odd junk over the years,
In one case, a Western Digital (!) XT-class machine I snagged a display
out of it. No problems with the LCD part of it, but it also appears to be
equipped with a backlight -- there's a separate lead coming out of it with
two wires going to an oddball 2-pin connector, both wires being the same
color. Your mention of EL backlights make me wonder if perhaps that's what
it is. Know of any easy way to find out?

 

[Michael]

Speaking of which...

I scrounge a lot of parts, scrapping all sorts of odd junk over the years,
In one case, a Western Digital (!) XT-class machine I snagged a display
out of it. No problems with the LCD part of it, but it also appears to be
equipped with a backlight -- there's a separate lead coming out of it with
two wires going to an oddball 2-pin connector, both wires being the same
color. Your mention of EL backlights make me wonder if perhaps that's what
it is. Know of any easy way to find out?

Put an ohmmeter across the leads ... both polarities ... and see if
there's a front/back R ratio. If there is, apply DC ... observing
proper polarity ... with a couple hundred ohms in series and the beastie
just might light up. If no front/back ratio, either the backlight is
LED and is toast or it's something other than LED.

 

[Roy J. Tellason]

:

Put an ohmmeter across the leads ... both polarities ... and see if
there's a front/back R ratio. If there is, apply DC ... observing
proper polarity ... with a couple hundred ohms in series and the beastie
just might light up. If no front/back ratio, either the backlight is
LED and is toast or it's something other than LED.

It's the "something other than" case I was wondering about...

I have no experience with EL devices, don't know what they want to see to
make 'em work. If I don't measure anything in either direction, is this
likely what I've got? Any pointers to info on such stuff?

 

[Jeff]

It's the "something other than" case I was wondering about...

I have no experience with EL devices, don't know what they want to see to
make 'em work. If I don't measure anything in either direction, is this
likely what I've got? Any pointers to info on such stuff?

They are a high value capacitor - you drive them at something around 100V at
100 to 500 Hz in most cases.

 

[Jeff]

They are a high value capacitor - you drive them at something around 100V at
100 to 500 Hz in most cases.

That should be a low value typically a few nF - time to get some sleep.

 

[S P O N I X]

They are a high value capacitor - you drive them at something around 100V at
100 to 500 Hz in most cases.

I have seen small fluorescent tubes used as backlights as
well...unlikely but still a possibility.

sPoNiX

 

[Roy J. Tellason]

I have seen small fluorescent tubes used as backlights as
well...unlikely but still a possibility.

Not in this one! The other LCD displays I have around here I'm pretty sure
are 2x16, they were pulls from Yamaha DX7 keyboards that were upgraded to
backlit displays. This one is *smaller*. I remembered that it was smaller
because I was going to build a little unit that would fit into a drive bay,
and hoped this one would, while the other ones were too big...

Not unless they make flourescent tubes a whole *LOT* smaller than I've ever
seen!