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Turning on LCD

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sgboi

New Member
can anyone give me some ideas on how to turn on all the pixel of a LCD panel? Is there a common pin or some pin i have to bias? no drivers at all, just the LCD panel. Dot matrix character.
 

Sebi

Active Member
For LCD pixel activation need reverse phase rectangular voltage against backplane (common). Frequency about 20...100Hz. For testing make short all row, and make short all columns. This two terminal can activate all pixels.
 

sgboi

New Member
thanks for the info.
sorry for my ignorance but where is the backplane?

do you mean shorting all the column pins together and the row pins together?

any pins i have to leave it floating?

do i have to connect them to some other places?

meaning i need to get the datasheet to know which is the column and the row pins?

is there any way to find out the pins configuration?

Sorry for asking so many things, cause its my first time dealing with LCD.
 

Sebi

Active Member
Don't leave any pin free. The free dots can activated by active neighbors.
I use this circuit for 7segment display.(LCD2.gif)
 

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sgboi

New Member
Thanks Sebi.
But is there that i can know which is the backplane without the datasheet?

And also is it the same method for testing Dot Matrix Character Lcd and Dot matrix graphic Lcd?
 

Sebi

Active Member
The character-LCD module have a driver chip with parallel or serial interface. My test-method works only with "naked" LCD. For testing equal backplane or dot-segment. If You have e.g. a four digit 7segment LCD with one backplane (not independent BP for each digit), this is always the pin1 and/or pin40.
 

sgboi

New Member
thanks Sebi, i can test a 7 segment lcd now. But could i use the same method in testing a character one? i know a character one has a controller and driver to light up the lcd but is there anyway to test it without the driver and controller?
 

sgboi

New Member
one more thing. is there any datasheet on the web which is for the "naked" lcd(dot matrix character). Most of them which i have found are the modules which already comes with the driver and controller.
 

Sebi

Active Member
I think today no more existiert the "naked" version of dot matrix LCD.(the driver circuit too complicated with many IC-s and expensive) The modules contains a driver, character generator,some flash for customer definied characters, and parallel or serial interface. In the very old time i've seen a few pieces, but - just thinking about - need one EXOR-gate for each dots for driving or staircase signal generator for multiplex-mode (DC-component of drivig signal not allowed)! So this method is dead.
 

sgboi

New Member
oh no... that means i can't test my dot matrix lcds. because my lcd has already been detached from tthe module.
 
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