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Re: [cosmacelf] Picture an 1802

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  • Lee Hart
    ... I was thinking that the LEDs could be driven by a long shift register. A really trivial 1802 program can write a pattern into the shift register, which
    Message 1 of 4 , Jan 7, 2010
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      Mark Graybill wrote:
      > The first thing I thought of when reading the idea of LEDs in the
      > frame is another "period" device: the infinity mirror. ;)

      I was thinking that the LEDs could be driven by a long shift register. A
      really trivial 1802 program can write a pattern into the shift register,
      which then runs around the border marquee-style. The program and
      instructions for loading it can be on the "picture", so interested
      viewers can toggle it in and try it.

      > I like the Lunar Lander game idea. I also like the idea of a clock on
      > the address displays when idle. Perhaps the data displays could
      > display the number of AU one of the Voyagers is from the Sun while the
      > clock is running. :)

      That would be cool. Though you'll probably need a many-digit LED display
      so the last several digits can be seen to be changing. Have it display
      miles to Earth!

      > Photocells sound great, too. I like to add them to my circuits when
      > possible. I recently got one of my daughters interested in them. Now I
      > have the happy circumstance that she's been raiding my parts drawers
      > for them, trying out different ones.

      On photocells: I have an idea for an inexpensive substitute for toggle
      switches. Use two LEDs as photodiodes. Wire them in series across the
      power supply, reverse polarity so they don't light or draw any current.
      Connect the junction between them to a CMOS gate. When light shines on
      the diode, it generates a tiny photocurrent. With the same light on both
      diodes, the photocurrent is the same and the voltage at the input to the
      CMOS gate is half the supply voltage.

      Now put a little flap or slider over the diodes that you can move to
      either of two positions (up/down). Up, it blocks room light from
      reaching the upper diode, so the lower diode's current pulls the gate
      input low. Down, the reverse happens, and the gate input goes high.

      --
      Lee A. Hart | Ring the bells that still can ring
      814 8th Ave N | Forget the perfect offering
      Sartell MN 56377 | There is a crack in everything
      leeahart earthlink.net | That's how the light gets in -- Leonard Cohen
    • Bill Rowe
      Now put a little flap or slider over the diodes that you can move to either of two positions (up/down). Up, it blocks room light from reaching the upper
      Message 2 of 4 , Jan 7, 2010
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        "Now put a little flap or slider over the diodes that you can move to
        either of two positions (up/down). Up, it blocks room light from
        reaching the upper diode, so the lower diode's current pulls the gate
        input low. Down, the reverse happens, and the gate input goes high."

        geez, I'll try that. It would work with your thumb too I bet.


        ----- Original Message -----
        From: Lee Hart
        To: cosmacelf@yahoogroups.com
        Sent: Thursday, January 07, 2010 12:26 PM
        Subject: Re: [cosmacelf] Picture an 1802



        Mark Graybill wrote:
        > The first thing I thought of when reading the idea of LEDs in the
        > frame is another "period" device: the infinity mirror. ;)

        I was thinking that the LEDs could be driven by a long shift register. A
        really trivial 1802 program can write a pattern into the shift register,
        which then runs around the border marquee-style. The program and
        instructions for loading it can be on the "picture", so interested
        viewers can toggle it in and try it.

        > I like the Lunar Lander game idea. I also like the idea of a clock on
        > the address displays when idle. Perhaps the data displays could
        > display the number of AU one of the Voyagers is from the Sun while the
        > clock is running. :)

        That would be cool. Though you'll probably need a many-digit LED display
        so the last several digits can be seen to be changing. Have it display
        miles to Earth!

        > Photocells sound great, too. I like to add them to my circuits when
        > possible. I recently got one of my daughters interested in them. Now I
        > have the happy circumstance that she's been raiding my parts drawers
        > for them, trying out different ones.

        On photocells: I have an idea for an inexpensive substitute for toggle
        switches. Use two LEDs as photodiodes. Wire them in series across the
        power supply, reverse polarity so they don't light or draw any current.
        Connect the junction between them to a CMOS gate. When light shines on
        the diode, it generates a tiny photocurrent. With the same light on both
        diodes, the photocurrent is the same and the voltage at the input to the
        CMOS gate is half the supply voltage.

        Now put a little flap or slider over the diodes that you can move to
        either of two positions (up/down). Up, it blocks room light from
        reaching the upper diode, so the lower diode's current pulls the gate
        input low. Down, the reverse happens, and the gate input goes high.

        --
        Lee A. Hart | Ring the bells that still can ring
        814 8th Ave N | Forget the perfect offering
        Sartell MN 56377 | There is a crack in everything
        leeahart earthlink.net | That's how the light gets in -- Leonard Cohen





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