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Help with power supply for CFAG320240CX-TFH-T-TS

bboldt

New member
I am having trouble operating a CFAG320240CX-TFH-T-TS
on mypowersupply, i am using a 7805 for the +5v and the MAX-749 to supply the -18.3V.
I cannot get the LCD to display, the small lines across the top and bottom begin to light up, so i know the -18.3 is correct. i jsut need any ones input on how to fine tune the supply for the logic as well as my 8 bit micro. i have gotten this setup to work on a lab supply, but i have tried working at this with a homeade supply for days now, and i have gotten no where. any input would be appreciated. Thank you.

Brad boldt

bboldt (at)purdue(dot)edu
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CF Tech

Administrator
Well, since you have a working situation (lab supplies) and a non working situation (MAX part) you should be able to just change one thing at a time until you can see what is going on.

However . . .

The CFAG320240CX-TFH-T-TS has a built in negative voltage supply, and a built-in potentiometer, so unless you want to have the contrast voltage under program control, you can just leave pin 3 (Vlcd) open and set the contrast pot on the back to make pin 3 the voltage what you want it to be. You should not need the MAX chip at all.
 

bboldt

New member
Help with interfacing

Thanks for your help. I was able to power up the LCD. However, now i am having trouble interfacing the LCD controller with the micro. I am using an 8MHz atmel ATmega32 for this. I have written the code, i was able to test it with functionality on a lab supply. However i recieve sparatic results, all of witch seem to relate to the logic supply voltage on the LCD. I got characters and graphics to print to the lcd when applying 5V to the micro and 3.2 volts to the lcd, however it would not work everytime, and i cannot get it to work with linear regulators. I checked them to ensure they could supply enough current, and they can. I think the issue has to do with the controller not understanding the correct logic levels. Do you have any advice as far as getting this to work?

thanks in advance
Brad
bboldt@purdue.edu
 
... However i recieve sparatic results, all of witch seem to relate to the logic supply voltage on the LCD. I got characters and graphics to print to the lcd when applying 5V to the micro and 3.2 volts to the lcd, however it would not work everytime, and i cannot get it to work with linear regulators...
The LCD logic supply is spec'd for 5 V, so why are you giving it 3.2 volts?
 
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