Light Logic - Diode Resistor Logic out of its cage

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

This a great example of what diodes can do. The sequencer is just diodes, resistors and caps. The display and matrix from the IO project uses diodes only.

I might as well add my seven step sequencer to the demo panel. This sequencer will find its way into my processor build this winter using only Light Logic circuits.

I am planning to add other Light Logic circuits to the panel in order to showcase the progress of developing these logic circuits. I will add the original S-R Latch, a gate using a 0402 SMD Led, my smallest 3 input NAND gate constructed and of course the new XOR and XNOR single gate modules. There will be more to come.

The demo panel now sports a working D-Latch flip-flop that includes a led driver in the form of a Buffer gate on the Q output. You might notice that the NAND gates have had their CdS voltage supply resistors removed. These NAND gates as wired do not need a voltage to indicate a ONE output. Indeed the output can be a floating 0 volts and still count as a ONE unless the following gate is either a OR or NOR gate. It is the ground connection that makes a firm ZERO output do the job. That is why I am using a Buffer for the output Led indicator.

Here are the four stages of Light Logic gate operation.

Switch setting 0,0

Switch setting 0,1

Switch setting 1,0

Switch setting 1,1