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Re: [smartsockets] IV-17 / IV-4 Smartsockets

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  • Quixotic Nixotic
    Does anyone know why the IV-17s are better than the IV-4s? What is the difference, electronically-speaking? John S
    Message 1 of 12 , Jan 11, 2009
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      Does anyone know why the IV-17s are better than the IV-4s? What is
      the difference, electronically-speaking?

      John S
    • Chris
      ... Sorry John, but the accuracy is important because the crystal is also the timebase for the USART serial port, although I am not sure to what extent a few
      Message 2 of 12 , Jan 11, 2009
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        --- In smartsockets@yahoogroups.com, John Rehwinkel <jrehwin@...> wrote:
        >
        > > To improve on that, I clocked the pic from an external 24MHz crystal,
        > > to get the SPI bus up to 6MHz, and now the fading is very smooth. The
        > > problem here is that the cost of the crystal could be more than you
        > > might pay just for one tube !
        >
        > Surplus is your friend. Electronics Goldmine has 24MHz crystals for a
        > dollar apiece. As they're surplus, they may not be the most accurate
        > crystals out there, but accuracy doesn't matter here. Goldmine
        > usually deals in quantity, so I suspect they have a large number
        > available, and may even give a discount on a quantity purchase.
        >
        > http://www.goldmine-elec-products.com/prodinfo.asp?number=G7147
        >
        > – John
        >

        Sorry John, but the accuracy is important because the crystal is also
        the timebase for the USART serial port, although I am not sure to what
        extent a few ppm of crystal error at 24MHz changes the port speed.
        I had some issues with internal oscillators running at 4MHz being
        slightly inaccurate.
      • Chris
        ... of power.... ... Yeah, but hopefully they won t ever say that ! I ve just done some real measurements and had a pleasant surprise. At 24V the long diagonal
        Message 3 of 12 , Jan 11, 2009
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          --- In smartsockets@yahoogroups.com, guus.assmann@... wrote:
          >
          > Wasting power is not good, as a general rule.
          > But in a case like this, it's such a small amount.
          > And one could also say that powering up any smartsocket is a waste
          of power....
          >

          Yeah, but hopefully they won't ever say that !

          I've just done some real measurements and had a pleasant surprise.
          At 24V the long diagonal segment (chosen because it was the longest)
          runs at about 140uA (microamps). As voltage rises so too will current,
          but it's probably enough for now to say that each segment draws 200uA,
          to be on the safe side.

          If , on average, only half of the segments are used, the average
          maximum current lost in the driver will be no more than about 2mA.

          Compared to a 'proper' VFD high side driver like the MAX6921, which
          draws about 1mA in idle mode, and has serial bus lines and blanking
          control lines which could easily add 10mA, using resistors and drivers
          seems to be less wasteful than a proper VFD driver is !(under certain
          circumstances ;o) )

          Now, looking again at the choice of driver IC's can anyone see
          anything wrong with using three ULN2003AD chips at 15 pennies each ?
          (less in larger quantities). They are rated to 50V with a relatively
          huge current capacity. I have some on the shelf so I think I'll give
          them a try in the next couple days.

          The other thing missing from the equation are the resistor networks
          which would be required to add current limiting to each segment which
          is to be shorted to ground, just pennies in terms of cost, but need to
          find room for them on the pcb too !

          Chris
        • Chris
          ... Apparently they live longer, and also draw slightly less current too.
          Message 4 of 12 , Jan 11, 2009
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            --- In smartsockets@yahoogroups.com, Quixotic Nixotic <nixotic1@...>
            wrote:
            >
            > Does anyone know why the IV-17s are better than the IV-4s? What is
            > the difference, electronically-speaking?
            >
            > John S
            >


            Apparently they live longer, and also draw slightly less current too.
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