What to look for in a display?

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Hi guys, I would like to start playing with some displays and I was wondering if any of you have some advice at what to look for or even some links to some good documentation.

I would like to play with some character moduals (simple 20x2 would be great) and some monochrome graphical displays (say 128x64).

The one thing I have already noticed is that some displays require 2 power supples a 5v and a 10v supply, I don't really like this.

I'm not a cartoon character but I play one in real life.

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Well, this datasheet is pretty universal and the initialization procedures are very simply put.

Hope it helps.

Note: It's only for character displays

BTW: Check out the projects section. There's a bazilion things with displays.

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There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

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Hi Qema,

All the LCD Mobules need a dual power supply to operate:
1. A 5.0V (or 3.3V or less, for the latest products) power supply for the logic (the controller and the drivers), between Vcc and GND.
2. A negative power supply in respect to Vcc, for the actual liquid crystal display part of the module. This negative supply can be anywhere between -2V and -25V, and it depends on the liquid crystal technology used.
3. A third power supply for the LCD Backlight --if it exists--, and it depends on the illumination source used (LED/EL/etc)

For example, the HD44780 compatible character modules need about -3.5V in respect to Vcc for the display, and since Vcc is 5.0V above GND, this supply can be provided by the GND level voltage through a buffered resistor voltage divider.
The graphic modules now, need a higher negative voltage supply than their little cousins do, which usually is -8V in respect to Vcc line voltage. It is obvious that the GND level voltage is insufficient for this job, so we have to generate that negative voltage, and it is usually done with charge-pumps. Of course, some newer graphic controllers have intergrated such a circuitry and we are only expected to provide the external charge-pump capacitors (which are huge in size in order to be also intergrated into the controller chip).
Conveniently for us, many of the LCD Module manufacturers include this negative voltage supply generator into their modules so the latter ones will only need a single power supply to operate.

After having solved their dual/tripple power supply requirement, the next thing to worry about with the LCD Modules is their instruction set, their data format and their possible extra capabilities (like character generation, multilayer rendering, shading, etc.)
But, as Daqq has already suggested, the better way to learn about the LCD Modules is to study their data sheets.

Have fun,
-George

I hope for nothing; I fear nothing; I am free. (Nikos Kazantzakis)

Last Edited: Thu. Jul 5, 2007 - 05:51 PM
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George: The -3.5V i thing is solved in some strange manner on most HD44780 comp. disps. as I have never seen any character display which would have other power requirements than : +5V, GND, CONTRAST. Maybe the HD44780 has the converter inside? Dunno

There are pointy haired bald people.
Time flies when you have a bad prescaler selected.

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Their Pin#3 (if I remember correctly), called Contrast Adjust, needs to be tied via a (variable) resistor to the GND line, to get the negative-in-respect-to-the-Vcc-voltage supply.

Remember: "-3.5V in respect to the Vcc voltage", which also is +1.5V above the GND line voltage when Vcc-GND = +5.0V, is still a negative voltage in respect to Vcc.

I hope for nothing; I fear nothing; I am free. (Nikos Kazantzakis)