LIGHT LOGIC - HIC SVNT DRACONES

January 14, 2022 - One thing I have decided on is that when Light Logic is used in toggle latching circuits I must be more precise in matching the LDRs for their lower resistance with the Leds I am using. Normal combination logic is not generally a problem but with a clocked toggle arrangement any major mismatch leads to problems in latching or holding a latch and I have to be real careful when adjusting the voltage for everything to work the way I want. Ahhh the trials and tribulations of Light Logic.

January 11, 2022 - Making a divide by 2 circuit with Light Logic and a astable oscillator also using vactrols has been quite the challenge. Far from being stable, it is a start and at least proves to me that Light Logic can do it all as long as I do not lose my mind in the process. The main logic is a Nand D Flip Flop along with a few other support gates.

Just messing and now have the rise and fall times getting much sharper. I made a slight mod to the left side of the circuit where I added a second LDR to the Led to act as the output so not loading the circuit. Caps are 470uf.

January 5, 2022 - Drifted back to fine tuning the Astable Multi-vibrator as a future clock to trigger a flip-flop counter. I could go with a simple relay but I want to give LL a fair chance. Light Logic does not need a square wave but the sharper the rise and fall time the better. Being a pair of caps are charging and discharging and a couple of CdS LDRs are in the mix, there will always be a lead and lag time to deal with.

Well, exclusive to All and Nothing OR Everything in between ;--)

I was messing with the XNOR circuit and this came up. Perhaps it

could be used as a lower and upper detection for a counter... I have no idea.

December 31, 2021

Not earth shattering but here are the final circuits for Light Logic. Happy New Year to everyone.

December 28, 2021 - After a bit of an absence I started improving on some of my Light Logic gate circuits. I was never satisfied with how my XNOR gate turned out so I ended up having a dream last night and when I woke up this morning I got to working on what I had dreamed about. The simple change is that I now feed 5 volts to the inputs continuously through a pair of 150R resistors. If there is no input at either A or B then the input is considered HIGH. If either A or B is grounded through a previous gate then the input is LOW. The Out of the LDR can be followed by a Light Logic Inverter gate to create a XOR gate or wired to any other gate as needed. I have this circuit on a bread board and it is working as it should. Remember, with Light Logic  the output MUST be through the LDR to ground to be a counted as a solid Zero / Low. Anything else is counted as a One / High

April 6, 2021 - Working with a free form idea of replacing input switching diodes with Leds. This is a 4 input NAND gate that shows the logic flow from input to output. This circuit works well with my existing Light Logic gates.

Input diodes are either to ground through a prior CdS LDR  for a zero or open for a one. Minimal stress on the input Leds as the CdS minimum resistance is at a safe level of about 300R or higher.

At long last I decided it was time to draw the circuit for the seven step sequencer. The switch shown is only needed if the circuit will not self start. Note that the outputs step by five. That gave me several headaches trying to figure that out......

Well, it's been a year now from when I started this Light Logic project and after a slow start it has come along nicely IMO.

Let me just list the successes I have had so far to date ( Oct 28, 2019 )

All the basic logic gates :

     Non Inverting Buffer, Not, And, Nand, Or, Nor, Xor and Xnor

S-R Flip Flop

D-Latch Flip Flop

Astable Clock Flip Flop

Seven Step Self Clocked Sequencer

One Bit Full Adder

Tri-State Buffer

From these building blocks I should be able to design a basic processor using only diodes and resistors as the main components and a hand full of capacitors for a sequencer.

This is so much fun......Can't wait for next year :-D

I have been working with Light Logic for over a year now and the name Light Logic fits quite well for the entire logic gate family ie. Not, And, Nand, Or etc....

What I have recently been looking into was a name for the Led/LDR pair and a few names have popped up such as....

NPV - Nesselhaus Photonic Valve @Starhawk 

IPV - Isolated Photo Varistor @Starhawk 

LLPT - Light Logic Photonic Transistor @Morning.Star 

Thanks for the cool ideas my friends.

But @Yann Guidon / YGDES  did some digging and came up with the Vactrol.

This opto-isolated buffer uses a Led coupled to a LDR in a very small package and the Vactrol name has been in use for quite a few years and used mainly in audio applications.

https://en.wikipedia.org/wiki/Resistive_opto-isolator

https://www.ebay.co.uk/itm/Audio-Optocoupler-Opto-Isolator-LED-LDR-package-vactrols-Circuit-Bending-/301866130538

So in the end I will follow along and use the name Vactrol for my Led/LDR pair.