LCD 7 segment vs. LED 7 segment display?

Discussion in 'General Electronics Chat' started by FastEddie, Mar 18, 2008.

  1. FastEddie

    Thread Starter Active Member

    Jul 14, 2007
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    Hi. I'm trying to make a small project that requires two 7 segment displays. I'm using a PIC 16F818 to run it. Due to the limited pins I multiplex(?) two 7 seg LEDs together using npn transistors. This seems to work pretty good, but I was wondering if I use LCDs instead...

    Can I multiplex LCDs as I could with LEDs?

    Battery life should be longer?

    Do I need a resistor in series with each segment, if so, any idea how much?

    I realized that the LCDs that I ordered (Mouser part# 696-LCD-S301C31TF), if I read the data sheet right operates on 5VAC and I'm using 5VDC. Will this work?

    Any thoughts are welcomed. Thanks in advance.
    Ed
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Similarly.

    Quite probably.

    The specifications don't indicate current utilization, and the link to their catalog on their website is not currently functioning. You should call them.

    According to the docs I've read, you must use AC. The absolute maximum limit specified for DC levels is 3V.

    See here:
    http://www.lumex.com/viewer.aspx?file=technotes/LCD_dispwodriv.html#Characteristics

    Their telephone #: 800-278-5666
     
  3. FastEddie

    Thread Starter Active Member

    Jul 14, 2007
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    I guess I'll have to get other ones. Or maybe a PIC that runs on 3V.
    Thanks,
    Ed
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    Ahh, that's not exactly what I meant ;)

    Why don't you give them a call, and verify what the requirements are for driving their LCDs?

    I DID see a couple schematics for power supplies for their products, but it's rather confusing because the power supply schematics were purely DC, whereas the "datasheet" specifies 5VAC for the exitation voltage, and in another location on their website it specifies absolute maximum to be 3VDC.

    Perhaps the exitation they require is simply 5v p/p with an average around 1v. I don't know. That's why I suggested you give them a call. It's a toll-free number.
     
  5. FastEddie

    Thread Starter Active Member

    Jul 14, 2007
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    Yeah, I'll call them first and see if they can be more specific.
    Thanks again
    Ed
     
  6. Nomad

    Active Member

    Oct 21, 2007
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    0
    batteries would definately last longer. if that pic supports it you can use it's hpwm to generate an ac source if needed. some 5v pics have a wide operating voltage range. the 16f628 will operate from as low as 2v up to 5.5v. i dont have access to the data sheet for yours to check. EDIT: just checked. yours does have hpwm and the wide operating voltage range!
     
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