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advice needed on variable resistors for LCD

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  • advice needed on variable resistors for LCD

    With that diagram everyone has for coupling LCD screens to printer ports;

    I notice there are two variable resistors needed for the brightness and contrast of the screen.

    1/ I dont know too much about electronics but I've built by own cables before, could anyone tell me what exact parts I need, ie: any particular wattage or type these variable resistors need to be. So I dont feel stoopid walking into Maplins explaining what I need for my project.

    I am going to order some $15 non backlit 4x40s from EIO

    John H

  • #2
    Use POT ... and connect it to pin 1, 2, 3. in between cable and 4x40 LCD..

    then you can adjust Resistor value using Pot.

    I used 100k (104, I think) and works fine..
    but not that broad range.. I had this so I just used for change brightness...

    You might try less pot resistor..

    [ 10-04-2001: Message edited by: helloman ]
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    • #3
      I wondered this myself at one time. I have Timeline's 40x4 Densitron backlit LCD display, and I found on the Densitron website that they recommend a 2.3 ohm resistor for the backlight. So, instead of trying to find a 100 ohm potentiometer, I simply wired 2 1-ohm resistors in series and as far as the contrast potentiometer, well, I find there is no need for it, as full contrast is the best for my particular display. So I have that connected directly to ground. LCD is beautiful and the brightness is as bright as it could possibly be without getting hot.