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30700Re: [midatlanticretro] Building a Better Tape Reader

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  • Mike Hatch
    May 15, 2013
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      This article I think you may have seen -

      Another -

      This article actually gives a few values, looks like a HE Green array
      might work the best -


      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.
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