• The Big Board

    Dr. Cockroach • 02/08/2023 at 13:40 • 0 comments

    March 13, 2023 - Making slow but steady progress. The copper foil is just about finished and starting to add more gate hardware.

    Feb 27, 2023 - Making steady but slow progress with the copper foil traces.




    Feb 24, 2023 - The upper half of the copper foil is now in place.

    I started adding input and function select switches. I might end up using another style switch, perhaps small toggles.






    February 19, 2023 - The first Bit Zero logic is in place and after some resistor value adjustments, the logic and the various inputs/selects match the online simulation as well as Logisim so I am ready to continue laying out the rest of the circuit.

    February 12, 2023 - Not super exciting but the first two Light Logic gates have made it to the Big Board. Both gates are NOT gates ( Inverters ).




    February 11, 2023 -  Started adding copper foil traces. I am using 1/4 inch copper foiling tape and splitting in half with a sharp blade.



    Entries below are the lead up to actually adding copper foil to the glass.

    Initial layout of where all the Light Logic gates will be located on the 20" X 16" glass plate. I was planning on strictly using copper foil for the traces but now thinking that a Circuit Scribe pen with silver ink will be easier to work with. The CS ink is said to be able to take solder if done carefully so I will order up a few of the pens next week and perform some tests.

    All 63 gate footprints are inked in.

    Testing how well the copper foilling tape on glass sticks. The foil tape will become loose when heated by soldering but soon regains a solid contact with the glass upon cooling.

    Starting to ink in the traces....

  • 74181 Functions

    Dr. Cockroach • 02/08/2023 at 01:31 • 0 comments

    February 19, 2023 - Spent most of today confirming the Function and Operations on a simulator and boy was my brain in a fog for awhile. I am shy of 70 years by just a few. I caught myself up to where I understand about 99 percent of what is shown below but two or three still do not sim out to what I am thinking they should be so I still need a bit more study time with this. My wife just says - Better you than me....

    This is what the 74181 can do........ And what the completed 74LL181 will do.

  • 74181 Circuit

    Dr. Cockroach • 02/08/2023 at 01:22 • 0 comments

    The classic 74181 ALU circuit uses very basic logic gates and is a perfect example of combinational logic.