30730Re: [midatlanticretro] Building a Better Tape Reader
- May 15, 2013On 05/15/2013 03:15 PM, Mike Loewen wrote:
>>>> When I was playing with my Arduino micro controller I read articlesI think that's an excellent idea. One could mold them into a little
>>>> 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
>>> 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.
"tub" of epoxy or similar, to make an optical read head.
Dave McGuire, AK4HZ
New Kensington, PA
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