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Sure this is a pretty basic question for you guys, but figured I'd start here. Is the linked LCD screen driven by some type of driver, or do you just supply logic voltage to whatever pin you want to illuminate on the LCD?

https://www.farnell.com/cad/2244525.pdf

So for example, if this were ran off of an Arduino, is there a better way to control the massive amount of pins? I know some of the Adafruit stuff has I2C and or SPI with library, but didn't see anything for this one.

Is the best way to do that to use an array for each position of the digit in order to illuminate? For example, if a rotary encoder were used just as a counter, each susequent counter step would be an array to supply voltage to the proper LCD lines? Maybe this could be done more simply with bit shifting? Just looking for any direction that someone may know.

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    \$\begingroup\$ LCD screens should be driven by AC voltage to avoid damage. Otherwise, yes, I believe you can just apply AC voltage to whichever pins you want to light up, since this display is not multiplexed. \$\endgroup\$
    – Criticizing Israel not allowed
    Commented Oct 6, 2020 at 17:32
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    \$\begingroup\$ you need a control chip if you want to use this with something like an arduino \$\endgroup\$
    – jsotola
    Commented Oct 6, 2020 at 17:39
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    \$\begingroup\$ LCDs require multiple level voltages to be applied across any single segment at different times ... the reason is that an LCD segment cannot have a net DC voltage level applied across it, otherwise damage occurs ... simplistically said, in any given second, any positive voltage across the segment must be offset by applying a negative voltage of equal duration \$\endgroup\$
    – jsotola
    Commented Oct 6, 2020 at 17:41
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    \$\begingroup\$ this one is dirt cheap ... no, it is not ... support circuitry is required to make it work \$\endgroup\$
    – jsotola
    Commented Oct 6, 2020 at 17:55
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    \$\begingroup\$ ww1.microchip.com/downloads/en/AppNotes/00000658B.pdf shows how these LCDs work, and shows a matrix method of driving segments. Matrix method is complicated, but reduces # of drive lines from nearly 30 to something much less - perhaps few enough for an Arduino. \$\endgroup\$
    – glen_geek
    Commented Oct 6, 2020 at 18:29

2 Answers 2

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The HT1621 LCD controller may work.

An arduino library exists for it.

https://duckduckgo.com/?q=HT1621+LCD&ia=web

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So for example, if this were ran off of an arduino, is there a better way to control the massive amount of pins?

Can't; you need a relatively specific control voltage, in an AC waveshape. Your Arduino simply hasn't got the hardware that makes that easy. ("many pins" means you'd need to literally switch a lot of pins at a relatively high rate, and that means Arduino-typical MCUs aren't the tool of choice – too few pins, too slow. Even if that weren't the case: you really want something specifically designed to drive LCDs, otherwise you'll just be burning power.)

You'll want a screen that includes that driver, or you want an external driver.

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  • \$\begingroup\$ Actually it's regularly done with two I/Os in opposite phase. \$\endgroup\$
    – Chris Stratton
    Commented Oct 6, 2020 at 18:37
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    \$\begingroup\$ @ChrisStratton yeah, I hit submit to quickly, see my edit from a couple of seconds ago - this is about the number of segments being hard to drive with an arduino of limited fanout. \$\endgroup\$
    – Marcus Müller
    Commented Oct 6, 2020 at 18:38

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