negative generator voltage of GLCD

Discussion in 'The Projects Forum' started by alarassi, Mar 12, 2010.

  1. alarassi

    Thread Starter Member

    Feb 6, 2010
    52
    0
    hello guys

    i'm using a glcd on a project, JHD12864e model! when i wanted to interface the glcd to microprocessor i found out that the glcd needs a negative voltage generator on its VEE pin ( pin No.18) of -10v for the GLCD driving! this model of JHD1284e glcd doesn't have the negative generator onboard!!

    i know some other types of glcd might have it onboard such as (AGM1264f glcd) but since i already bought this JHD12864e glcd and want to use it, is there any possible way to generate this -10v on the VEE pin??

    attached is the datasheet for JHD12864 glcd and u can see on page9 (power supply) that there's no -10V while in last page says that i need to interface it to -10V !!

    thank you
     
    Last edited: Mar 12, 2010
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Do you only have a 5v supply available? Is that the problem?

    We don't know where you are, and this may make it difficult to recommend components/suppliers. It helps a great deal if you put that information in your profile. Use the "User CP" link to edit your profile. You do not have to be overly specific; country and state or province is fine.
     
  3. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    1,015
    69
    There are quite a few voltage converter ICs, like SCI7661 and MAX681.

    These use a charge pump system with a couple of small capacitors to produce negative and/or double voltage from the supply.

    The MAX680 or MAX681 may be your best choice, that will give -10 from +5V.

    http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1530
     
  4. alarassi

    Thread Starter Member

    Feb 6, 2010
    52
    0
    can you guys have a look at the datasheet for JHD12864e glcd and also the one for AGM1264f glcd (power supply section and VEE fucntion )and then compare the differences between their power supplies as well as Vee function!?

    i'm worried that i might misunderstand the things here and i shouldn't use voltage converter in my case!
    should i use -10V voltage generator at the output of Vee or no need? if yes, is it possible by using negative voltage converter as suggested to me?

    thank you
     
  5. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    JHD12864e.pdf:
    Page 17 (last page) for Interfacing LCD Driving (Vee) '-10v' needed on pin 18.

    BUT looking at the power supply diagram, they have 5v to Vdd, then a 10k Variable Resistor connected to vdd in line to Vee. So it appears, you do not need - voltage.
    [​IMG]

    AND in the maximum ratings, it says you can have +.03v on Vee. So i think its nuts.

    It says, single supply for voltage. So I would follow the posted power supply wiring.

    It must have a negative power generator on board.
     
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  6. alarassi

    Thread Starter Member

    Feb 6, 2010
    52
    0
    do u mean that it has a negative voltage generator already implemented onboard?

    what made me confused was that when i looked at the power supply diagram of AGM1264f i found the -10V stated there while not stated in my glcd!
     
  7. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    Thats what im guessing. Following the datasheet is the way to go. And it says one wire voltage connection.

    So I would do it exactly as the datasheet says:
    [​IMG]

    VDD to pin 1 of the variable resistor, Vo to pin 2 (the wiper) of the variable resistor and Vee to pin 3 of the variable resistor.
     
  8. alarassi

    Thread Starter Member

    Feb 6, 2010
    52
    0
    i connected the glcd and measured the voltage at pin18 and it wasn't -10V !!!
    i really don't know if i shoud use -10v voltage converter on my glcd or no?
    anyone has used JHD12864e glcd can answer me pls?
     
  9. avrsanju

    New Member

    Jul 22, 2010
    1
    0
    ur problem solved regarding glcd?..if so pls reply me ur solution...
     
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