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Optical Bench REDUX: Digital Switching can have Analog Functions!

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RJHayward:
Hi there:
   Continued from previous thread, on using Solar Yard Lights, for investigating various switched networks, without interconnecting wires.
   Having some difficulties, getting (proper) experiment settings, and especially, focus on 'edge trigger' logic.  The gist of this is, a solar light contains a (digital) switch, for only operating at night, by using the very same little solar 'panel' as a light sensor.  So, in digital terms, you have a means for 'mixing' various inputs, that are then combined into a totalized 'analog' input, for the level check.  If threshold is exceeded, that means the solar light is now in substantial (ambient) light and will shut off the LED output.
That is basically a 'logical NOR' gate, obviously also useful for 'And gate' functions, equivalent.
  An interesting aside to this; the little yard lights can be operated / switched, by application of two signal 'inputs', optically, where each input is (barely) above
50 %. There things, roughly speaking, can start to resemble neurons, where various input synapses bring analog coded signals for combination.  Of course, there isn't any 'negative' polarity of light, in same sense as electric, plus and minus, but the meanings can still be carried: Most signals, into the solar light, are 'inhibitory' anyway, and inverted logic can conveyed, this time by presence, or lack of presence (of any light).
But in general the inhibitory and actuating aspects can both be expressed, in collections of yard lights, into various relation structures, (like a simple 2-state flip-flop).
   Picture shows, a causally built 'Optical Bench', having top with many mounting holes, for putting gates (yard lights) individually related.  Underneath, is provided various battery packs and solder less proto boards.
A LED blinker provides a light source, for some testing.

RJHayward:
In this enclosed photo, I'm showing the difficult process, of obtaining a decent 'EDGE TRIGGER' on the light beam, from a first 'gate' and to the left, is seen a second gate, meant to be an inverter, in a classic edge detecting circuit (although here it is optical, not electric).  Problem was, mainly with various light levels, in that little, 3 component circuit.  For solving that, edge detector circuit, it was necessary to separate the solar panel (optical input), from the direction the output LED is pointing.  This way, the third gate, will get the full LED output, even while that 2nd gate is no longer inline...the output direction has been manipulated, just do that mechanical alignments are correct (for transfer of enough light to cause switching).
   If all that works, should be able to reproduce those very short pulses of light output, that I've already verified, (but on more 'shakey' informal experiments.)
The classic principal is simple: A delay through an inverter causes a short 'AND' condition to be satisfied, so an electrical pulse output happens. Then, as the inverter catches up, in matter of nanoseconds, the AND gate output goes 'false'.

RJHayward:
This photo showing the transient light (gate on the left) is off, in this view.

RJHayward:
(this view) shows the transient light gate inverter, with LED output ON.

RJHayward:
This current photo shows a kind of dual-nature, in the sense that, in upper, first example it's all digital, gate to gate, while second example, (lower in photo), shows two inputs, reaching the 100% threshold by combined intensity of light input. 
   So can have either, it really depends on context of use, whether you are getting a 'NOR', (with equiv AND, of 'not' inputs), or you are getting a 'NAND', style, where both inputs are needed, to get a logical output (zero).
It's a bit muddied, by the mixing of analog terminology, for inputs, unusual, with typical digital resolved output.

   For more 'context' illustration, a good example can be a design, for an optically sequenced A to D converter, acting to monitor ambient light levels.
By running a 'calibrated' light source into a gate, for comparison with ambient levels, it can be determined when the threshold is crossed, of a TOTAL light input.
So, let's assume today's light is at '30 %' ...an arbitrary number.  Then, by essentially adding in a D to A generated 'light' signal, the 100 % threshold is crossed when your D to A output climbs up to 70%. Thus you get a reversed or inverted answer result that can easily be inverted, to the correct result, of 30%.
The method is classic A to D by creating a source, via a D to A, for comparison.  Either a ramp style, (slow), or a successive approximation style can be used, in the A to D scheme.
   For the OPTICAL A to D subsystem, each of 4 bits are  (individually) raised, then tested, against AMBIENT, and subsequently canceled, if the trial (light level) went too high. That happens 4 times, for each bit (weight).
At the end, you have a 4 bit result, inverted, but it's an analog measure, of ambient light level.
The sequencer and test logic involves some thing on the order of 40 to 50 of those little yard lights.  Makes for interesting and intriguing exploration of digital analog, and neurological concepts, for sure!

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