30700Re: [midatlanticretro] Building a Better Tape Reader
- May 15, 2013Hi,
This article I think you may have seen -
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:
> 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:* email@example.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
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