Loading ...
Sorry, an error occurred while loading the content.

Re: [midatlanticretro] Building a Better Tape Reader

Expand Messages
  • Mike Hatch
    Hi, This article I think you may have seen - http://www.thebox.myzen.co.uk/Workshop/LED_Sensing.html Another - http://www.robotroom.com/ReversedLED.html This
    Message 1 of 11 , May 15, 2013
    • 0 Attachment
      Hi,

      This article I think you may have seen -
      http://www.thebox.myzen.co.uk/Workshop/LED_Sensing.html

      Another -
      http://www.robotroom.com/ReversedLED.html

      This article actually gives a few values, looks like a HE Green array
      might work the best -
      http://www.instructables.com/id/LEDs-as-light-sensors/

      Regards,
      Mike.
      www.soemtron.org

      On 15/05/2013 13:04, DuaneCraps wrote:
      > Mike,
      > Thanks for the input
      > The only gotcha that I remember is that the LED’s have a memory effect
      > due to the capacitance across the P-N junction causing it to tend to
      > hold a charge. Some people have used gates to clamp the LED to ground
      > between readings.
      > *From:* Mike Hatch <mailto:mike@...>
      > *Sent:* Wednesday, May 15, 2013 4:29 AM
      > *To:* midatlanticretro@yahoogroups.com
      > <mailto:midatlanticretro@yahoogroups.com>
      > *Subject:* Re: [midatlanticretro] Building a Better Tape Reader
      >
      > On 14/05/2013 21:19, DuaneCraps wrote:
      > > When I was playing with my Arduino micro controller I read articles
      > > about using led’s as light detectors.
      > > It got me thinking .....
      > > led bar graphs displays have .1 inch spacing to fit in DIP sockets .
      > > My idea is to use 2 bar graphs one as a light source and one one as the
      > > sensor.
      >
      > Interesting idea.
      > I have seen leds used successfully on on solar trackers and having used
      > leds for sensing in component counters before you might find you need a
      > mask over the sensor array, with a line of holes at 0.1" spacing to stop
      > bleed (laterally) from one track to its neighbour. Also to stop bleed
      > from one row (longitudinally) to the next as individual segments in led
      > bar-graph displays are usually quite longer than they are wide.
      >
      > > I did bread board one segment feeding an OP Amp with a 10K feedback
      > > resistor and got a
      > > 0 to 3.7 volt change with my LED flashlight through a sprocket hole
      > > sized hole.
      >
      > The emitter array may need some tweaking on the current as well to get
      > usable signals.
      >
      > Food for thought though, might just try it, I have some old PDP-7 tapes
      > I want to read.
      >
      > > If anyone wants to run with this, go ahead, you can have the glory
      > > Duane
      >
      > Regards.
      > Mike.
      >
      >
    • Dave McGuire
      ... Forrest Mims popularized the use of LEDs in photodiode mode in the early 1970s, and has done quite a bit with them. But...with real photodiodes and
      Message 2 of 11 , May 15, 2013
      • 0 Attachment
        On 05/15/2013 04:29 AM, Mike Hatch wrote:
        >> When I was playing with my Arduino micro controller I read articles
        >> about using led’s as light detectors.
        >> It got me thinking .....
        >> led bar graphs displays have .1 inch spacing to fit in DIP sockets .
        >> My idea is to use 2 bar graphs one as a light source and one one as the
        >> sensor.
        >
        > Interesting idea.
        > I have seen leds used successfully on on solar trackers and having used
        > leds for sensing in component counters before you might find you need a
        > mask over the sensor array, with a line of holes at 0.1" spacing to stop
        > bleed (laterally) from one track to its neighbour. Also to stop bleed
        > from one row (longitudinally) to the next as individual segments in led
        > bar-graph displays are usually quite longer than they are wide.
        >
        >> I did bread board one segment feeding an OP Amp with a 10K feedback
        >> resistor and got a
        >> 0 to 3.7 volt change with my LED flashlight through a sprocket hole
        >> sized hole.
        >
        > The emitter array may need some tweaking on the current as well to get
        > usable signals.
        >
        > Food for thought though, might just try it, I have some old PDP-7 tapes
        > I want to read.

        Forrest Mims popularized the use of LEDs in photodiode mode in the early
        1970s, and has done quite a bit with them.

        But...with real photodiodes and phototransistors available for pennies, I'm
        note sure of what the point would be, other than for hack value.

        -Dave

        --
        Dave McGuire, AK4HZ
        New Kensington, PA
      • Dave McGuire
        ... The capacitance is a direct function of the junction area; smaller LEDs will work better here. -Dave -- Dave McGuire, AK4HZ New Kensington, PA
        Message 3 of 11 , May 15, 2013
        • 0 Attachment
          On 05/15/2013 08:04 AM, DuaneCraps wrote:
          > The only gotcha that I remember is that the LED’s have a memory effect due to
          > the capacitance across the P-N junction causing it to tend to hold a charge.
          > Some people have used gates to clamp the LED to ground between readings.

          The capacitance is a direct function of the junction area; smaller LEDs
          will work better here.

          -Dave

          --
          Dave McGuire, AK4HZ
          New Kensington, PA
        • Mike Loewen
          ... How about using optical fiber to position the output from the emitters, and on the other side to the phototransistors? You should be able able to get the
          Message 4 of 11 , May 15, 2013
          • 0 Attachment
            On Wed, 15 May 2013, Dave McGuire wrote:

            > On 05/15/2013 04:29 AM, Mike Hatch wrote:
            >>> When I was playing with my Arduino micro controller I read articles
            >>> about using led?s as light detectors.
            >>> It got me thinking .....
            >>> led bar graphs displays have .1 inch spacing to fit in DIP sockets .
            >>> My idea is to use 2 bar graphs one as a light source and one one as the
            >>> sensor.
            >>
            >> Interesting idea.
            >> I have seen leds used successfully on on solar trackers and having used
            >> leds for sensing in component counters before you might find you need a
            >> mask over the sensor array, with a line of holes at 0.1" spacing to stop
            >> bleed (laterally) from one track to its neighbour. Also to stop bleed
            >> from one row (longitudinally) to the next as individual segments in led
            >> bar-graph displays are usually quite longer than they are wide.
            >>
            >>> I did bread board one segment feeding an OP Amp with a 10K feedback
            >>> resistor and got a
            >>> 0 to 3.7 volt change with my LED flashlight through a sprocket hole
            >>> sized hole.
            >>
            >> The emitter array may need some tweaking on the current as well to get
            >> usable signals.
            >>
            >> Food for thought though, might just try it, I have some old PDP-7 tapes
            >> I want to read.
            >
            > Forrest Mims popularized the use of LEDs in photodiode mode in the early
            > 1970s, and has done quite a bit with them.
            >
            > But...with real photodiodes and phototransistors available for pennies, I'm
            > note sure of what the point would be, other than for hack value.

            How about using optical fiber to position the output from the emitters,
            and on the other side to the phototransistors? You should be able able to
            get the desired spacing that way.


            Mike Loewen mloewen@...
            Old Technology http://sturgeon.css.psu.edu/~mloewen/Oldtech/
          • Dave McGuire
            ... I think that s an excellent idea. One could mold them into a little tub of epoxy or similar, to make an optical read head. -Dave -- Dave McGuire, AK4HZ
            Message 5 of 11 , May 15, 2013
            • 0 Attachment
              On 05/15/2013 03:15 PM, Mike Loewen wrote:
              >>>> When I was playing with my Arduino micro controller I read articles
              >>>> about using led?s as light detectors.
              >>>> It got me thinking .....
              >>>> led bar graphs displays have .1 inch spacing to fit in DIP sockets .
              >>>> My idea is to use 2 bar graphs one as a light source and one one as the
              >>>> sensor.
              >>>
              >>> Interesting idea.
              >>> I have seen leds used successfully on on solar trackers and having used
              >>> leds for sensing in component counters before you might find you need a
              >>> mask over the sensor array, with a line of holes at 0.1" spacing to stop
              >>> bleed (laterally) from one track to its neighbour. Also to stop bleed
              >>> from one row (longitudinally) to the next as individual segments in led
              >>> bar-graph displays are usually quite longer than they are wide.
              >>>
              >>>> I did bread board one segment feeding an OP Amp with a 10K feedback
              >>>> resistor and got a
              >>>> 0 to 3.7 volt change with my LED flashlight through a sprocket hole
              >>>> sized hole.
              >>>
              >>> The emitter array may need some tweaking on the current as well to get
              >>> usable signals.
              >>>
              >>> Food for thought though, might just try it, I have some old PDP-7 tapes
              >>> I want to read.
              >>
              >> Forrest Mims popularized the use of LEDs in photodiode mode in the early
              >> 1970s, and has done quite a bit with them.
              >>
              >> But...with real photodiodes and phototransistors available for pennies, I'm
              >> note sure of what the point would be, other than for hack value.
              >
              > How about using optical fiber to position the output from the emitters,
              > and on the other side to the phototransistors? You should be able able to
              > get the desired spacing that way.

              I think that's an excellent idea. One could mold them into a little
              "tub" of epoxy or similar, to make an optical read head.

              -Dave

              --
              Dave McGuire, AK4HZ
              New Kensington, PA
            • Mike Hatch
              On 15/05/2013 19:47, Dave McGuire wrote: I think the main idea Duane had was the readily available array form of a led bar graph module on a pitch
              Message 6 of 11 , May 16, 2013
              • 0 Attachment
                On 15/05/2013 19:47, Dave McGuire wrote:
                <..snipped>

                I think the main idea Duane had was the readily available array form of
                a led bar graph module on a pitch to suit the paper tape, rather than
                having to arrange individual components. I might give it a try just for
                the fun of it.

                Mike.

                >
                > Forrest Mims popularized the use of LEDs in photodiode mode in the early
                > 1970s, and has done quite a bit with them.
                >
                > But...with real photodiodes and phototransistors available for pennies, I'm
                > note sure of what the point would be, other than for hack value.
                >
                > -Dave
                >
                > --
                > Dave McGuire, AK4HZ
                > New Kensington, PA
                >
                >
                > Reply via web post
                > <http://groups.yahoo.com/group/midatlanticretro/post;_ylc=X3oDMTJybWI1ZW5lBF9TAzk3MzU5NzE0BGdycElkAzE0Mzc5MDMyBGdycHNwSWQDMTcwNTU2NjE2MgRtc2dJZAMzMDcxNARzZWMDZnRyBHNsawNycGx5BHN0aW1lAzEzNjg2NDM2NDg-?act=reply&messageNum=30714>
                > Reply to sender
                > <mailto:mcguire@...?subject=Re%3A%20%5Bmidatlanticretro%5D%20Building%20a%20Better%20Tape%20Reader>
                > Reply to group
                > <mailto:midatlanticretro@yahoogroups.com?subject=Re%3A%20%5Bmidatlanticretro%5D%20Building%20a%20Better%20Tape%20Reader>
                > Start a New Topic
                > <http://groups.yahoo.com/group/midatlanticretro/post;_ylc=X3oDMTJmaXBjZDhqBF9TAzk3MzU5NzE0BGdycElkAzE0Mzc5MDMyBGdycHNwSWQDMTcwNTU2NjE2MgRzZWMDZnRyBHNsawNudHBjBHN0aW1lAzEzNjg2NDM2NDg->
                > Messages in this topic
                > <http://groups.yahoo.com/group/midatlanticretro/message/30619;_ylc=X3oDMTM3anBwMjB2BF9TAzk3MzU5NzE0BGdycElkAzE0Mzc5MDMyBGdycHNwSWQDMTcwNTU2NjE2MgRtc2dJZAMzMDcxNARzZWMDZnRyBHNsawN2dHBjBHN0aW1lAzEzNjg2NDM2NDgEdHBjSWQDMzA2MTk->
                > (6)
                >
                >
              • Mike Hatch
                Hi, ... Simplicity, if it works, readily available modules on the right pitch. No fiddling with light guides, optical fibre. But I would want to know if there
                Message 7 of 11 , May 16, 2013
                • 0 Attachment
                  Hi,

                  On 15/05/2013 20:15, Mike Loewen wrote:
                  > On Wed, 15 May 2013, Dave McGuire wrote:
                  > > But...with real photodiodes and phototransistors available for
                  > pennies, I'm
                  > > note sure of what the point would be, other than for hack value.
                  >
                  > How about using optical fiber to position the output from the emitters,
                  > and on the other side to the phototransistors? You should be able able to
                  > get the desired spacing that way.

                  Simplicity, if it works, readily available modules on the right pitch.
                  No fiddling with light guides, optical fibre. But I would want to know
                  if there was any "bleed" from adjacent channels within the packages.

                  Mike.

                  > Mike Loewen mloewen@...
                  > <mailto:mloewen%40cpumagic.scol.pa.us>
                  > Old Technology http://sturgeon.css.psu.edu/~mloewen/Oldtech/
                  >
                  >
                  > Reply via web post
                  > <http://groups.yahoo.com/group/midatlanticretro/post;_ylc=X3oDMTJyOThsMXR0BF9TAzk3MzU5NzE0BGdycElkAzE0Mzc5MDMyBGdycHNwSWQDMTcwNTU2NjE2MgRtc2dJZAMzMDcyMgRzZWMDZnRyBHNsawNycGx5BHN0aW1lAzEzNjg2NDUzNjU-?act=reply&messageNum=30722>
                  > Reply to sender
                  > <mailto:mloewen@...?subject=Re%3A%20%5Bmidatlanticretro%5D%20Building%20a%20Better%20Tape%20Reader>
                  > Reply to group
                  > <mailto:midatlanticretro@yahoogroups.com?subject=Re%3A%20%5Bmidatlanticretro%5D%20Building%20a%20Better%20Tape%20Reader>
                  > Start a New Topic
                  > <http://groups.yahoo.com/group/midatlanticretro/post;_ylc=X3oDMTJmbThqaWhxBF9TAzk3MzU5NzE0BGdycElkAzE0Mzc5MDMyBGdycHNwSWQDMTcwNTU2NjE2MgRzZWMDZnRyBHNsawNudHBjBHN0aW1lAzEzNjg2NDUzNjU->
                  > Messages in this topic
                  > <http://groups.yahoo.com/group/midatlanticretro/message/30619;_ylc=X3oDMTM3ZDNncHZiBF9TAzk3MzU5NzE0BGdycElkAzE0Mzc5MDMyBGdycHNwSWQDMTcwNTU2NjE2MgRtc2dJZAMzMDcyMgRzZWMDZnRyBHNsawN2dHBjBHN0aW1lAzEzNjg2NDUzNjUEdHBjSWQDMzA2MTk->
                  > (8)
                  >
                Your message has been successfully submitted and would be delivered to recipients shortly.