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A project log for LLTP - Light Logic Transistorless Processor

My attempt to create a CPU/MCU without transistors or relays

Dr. CockroachDr. Cockroach 11/01/2021 at 21:527 Comments

November 1, 2021 - Finally finished up the newest D-Latch with a added output buffer. This build works just as well as the wall mounted LLTP D-Latches and is about as small as I can make with my standard way of hand making my Vactrols. The solder side is not pretty but the same layout as if it were a PCB.

Just to recap, the added output buffer is needed as the Q output can be de-latched when fed directly to the next stage such as a adder or another part of the processor.

Discussions

Dr. Cockroach wrote 11/04/2021 at 20:07 point

It would be interesting if I could find some old photo resistors/tubes from the 40's. I know that sound pickup on many 16mm home movie projectors used them back in the day. That's what I love about electronics as a hobby, so many what if's and I like to go into retro mode to see what could have been done years ago. Photo resistor copper plates existed back in the 1800's but I have no way of knowing the resistance values unless I make my own plates. Those same plates could also produce a small current when exposed to light. I have that info here somewhere but not ready to go down that rabbit hole just yet ;-)

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Dr. Cockroach wrote 11/02/2021 at 22:50 point

True except you should read up on my reason for Light Logic and making my own Vactrols from scratch. I have tried using a SMD Led mounted to the LDRs but I have very poor eyesight for such soldering and I have several thousand standard size Leds already in my stock as well a 1000 LDRs ;-)

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Gravis wrote 11/02/2021 at 23:27 point

OK.  Please post some schematics of your various circuits.  I'm somewhat interested in replicating them using SMD parts.  I managed to think about it and look over enough parts that I think you could put emitter/photo diodes on opposing sides of a PCB and use the PCB itself to shield the light.

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Dr. Cockroach wrote 11/03/2021 at 08:21 point

Actually the circuits/schematics are buried in my project pages. Your idea of using a PCB that way sounds interesting and doable. I am steering clear of photo diodes for LL as I have tried them but needed additional transistors to read the diode output signal and my goal is to not use any transistors. If a photo diode could interact directly with the next gate to act as a path to ground then I would try again and I still might give them a try later as I do have about 30 of them here. Check out this other page of mine that shows the circuit I am using....

https://hackaday.io/project/161669-light-logic-hic-svnt-dracones

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Gravis wrote 11/02/2021 at 12:40 point

If you are looking to reduce size then it's logical to use SMD components which range from small to "so small it only exists if you're looking at it".  If you need help, I have skills I can offer in that regard.

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Dr. Cockroach wrote 11/02/2021 at 23:00 point

Actually I do thank you for the help offer. My whole point in pursuing Light Logic was to see if this kind of logic device could have existed 100 or more years in the past IF anyone had just thought of it. I have made my gates work with a grain of wheat bulb and photo resistor so digital processors could have existed much sooner. As for speed...... Slow as snails compared to today's tech but I just love to see what could have been done :-) 

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Gravis wrote 11/04/2021 at 13:56 point

I did some digging and found that 1940s photoresistors were tubes that were only good for about 5000 uses and they didn't carry much power when they did work.  Chemical deposition based components really changed things in the 1950s around the same time as the invention of the transistor.

An early computer would have had to have been electromechanical... but I had another idea.  Galena crystal diodes and radio coils were also 1800s tech, so it might be possible to make a reliable switching mechanism with those.

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