LCD Partially Working

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Hi,

I have this LCD screen :: http://cgi.ebay.co.uk/ws/eBayISAPI....&category=26206&sspagename=STRK:MEBWN:IT&rd=1

At 3V its works fine. Text displays perfectly. BUT the contrast is VERY low, text is next to invisible to see.

I put power up to 4.5V and the contrast is great! But the text wont display correctly all comes out in $$$$$ signs and solid blocks, Ican see parts of texts flying accross the screen. but its not readable at all.

It cant be a wiring problem because it works at 3v just no contrast...

Can anyone think what is up?

P.S. The backlight IS working.

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This is the schematic i used

 

[CF Tech]

Try this circuit, which has been floating about the web for some time:

You basically need a limiting resistor on your backlight, a potentiometer on Vo and grounds from the parallel port to the LCD at a minimum.

The potentiometer will allow you to change the contrast setting without changing the LCD's logic voltage.

Read this thread for instructions on how to do the backlight limiting resistor.

 

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Hi,

im not all that good with electronics... but how will adding a limiting resistor fix the garbled information on being displayed on my LCD?

Thanks.

 

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Ok its been a while thought id bumpm the thread and add some more info...

On the back there is like 5 chips one is the HD44780 but it says HD44780A00

anyone know if this LCD is even workable lol ?