2014:vacuum_tube_sr_latch
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2014:vacuum_tube_sr_latch [2014/12/18 00:44] fbourke |
2014:vacuum_tube_sr_latch [2014/12/18 23:43] (current) fbourke |
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| + | ====== Vacuum Tube SR Latch ====== | ||
| + | with Forrest & Ruby | ||
| + | ^ Our 12AX7 Vacuum Tubes ^ | ||
| + | | {{ 2014:img_4256b.jpg?1024 }} | | ||
| ====== Abstract ====== | ====== Abstract ====== | ||
| We investigated 1940s era computers—esp. the [[http://en.wikipedia.org/wiki/ENIAC|ENIAC]] (Electronic Numerical Integrator And Computer)—and, using this knowledge, designed and constructed a basic bistable functioning element used in digital computers—the Set-Reset Latch, or simply SR Latch. Our ENIAC-based SR Latch design uses four triode vacuum tubes, basic analog components, and optional neon lights for output state indication. | We investigated 1940s era computers—esp. the [[http://en.wikipedia.org/wiki/ENIAC|ENIAC]] (Electronic Numerical Integrator And Computer)—and, using this knowledge, designed and constructed a basic bistable functioning element used in digital computers—the Set-Reset Latch, or simply SR Latch. Our ENIAC-based SR Latch design uses four triode vacuum tubes, basic analog components, and optional neon lights for output state indication. | ||
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| ====== What we did ====== | ====== What we did ====== | ||
| - | %This portion can assume an audience that has taken Computer Architecture, but don't get burdened by buzzwords. A sure sign of a bad engineer is over reliance on acronyms. | ||
| - | TODO How to read tube diagram | ||
| - | TODO Explanation of parameters | ||
| - | |||
| ===== Re-designing from ENIAC Documentation ===== | ===== Re-designing from ENIAC Documentation ===== | ||
| + | Our design is based around the design we found in this [[http://archive.computerhistory.org/resources/text/Knuth_Don_X4100/PDF_index/k-8-pdf/k-8-r5367-1-ENIAC-circuits.pdf|paper]]. | ||
| + | |||
| There are a few "quirks" modern engineers may not be used to when reading the documentation for ENIAC. The first and most obvious is what we call an SR Latch, they call a flip-flop. In current parlance, flip-flops are clocked elements while latches are not—ours are simply transparent. | There are a few "quirks" modern engineers may not be used to when reading the documentation for ENIAC. The first and most obvious is what we call an SR Latch, they call a flip-flop. In current parlance, flip-flops are clocked elements while latches are not—ours are simply transparent. | ||
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| ====== Building up from an SR Latch ====== | ====== Building up from an SR Latch ====== | ||
| - | %TODO: Include everything necessary to pick up where you left off. This should include: | ||
| - | \begin{itemize} | ||
| - | \item Code | ||
| - | \item Schematics notes on simulation | ||
| - | \item Build Instructions | ||
| - | \item List of difficulties and gotchas while doing the project | ||
| - | \item Work Plan reflection (OOPS) | ||
| - | \item Possible TODO to extend the depth of the project | ||
| - | \item ZIP file to submit to the wiki | ||
| - | \end{itemize} | ||
| - | |||
| ===== The Circuit ===== | ===== The Circuit ===== | ||
| Line 76: | Line 67: | ||
| To provide the 12V for the heaters, we simply purchased a modern switched-mode 12V power supply. In reality, the heaters would have most likely been fed from a transformer tap specifically designed to power the heaters. To provide the 165V for the positive rail, we simply directly rectified a 110V mains input and filtered it with a 120μF photoflash capacitor. For increased safety, it would have been better to use an isolation transformer, but we will leave this improvement for future engineers. | To provide the 12V for the heaters, we simply purchased a modern switched-mode 12V power supply. In reality, the heaters would have most likely been fed from a transformer tap specifically designed to power the heaters. To provide the 165V for the positive rail, we simply directly rectified a 110V mains input and filtered it with a 120μF photoflash capacitor. For increased safety, it would have been better to use an isolation transformer, but we will leave this improvement for future engineers. | ||
| + | |||
| + | We tried several spice models, but we found the best ones [[http://www.duncanamps.com/technical/ltspice.html|here]]. | ||
| ===== Mechanical Design ===== | ===== Mechanical Design ===== | ||
| Line 83: | Line 76: | ||
| ^ Render of our Mechanical Design. ^ | ^ Render of our Mechanical Design. ^ | ||
| | {{ 2014:isorender.jpg?840 | Render of our mechanical design}} | | | {{ 2014:isorender.jpg?840 | Render of our mechanical design}} | | ||
| + | ^ Our Finished Box ^ | ||
| + | | {{ 2014:img_4257b.jpg?840 }} | | ||
| ===== Analysis of Our Plan ===== | ===== Analysis of Our Plan ===== | ||
| - | We stated that building an SR latch was a yellow "intermediate" goal, and we're happy to have accomplished this. We did investigate doing other digital logic with vacuum tubes. We found a source called [[http://www.quadibloc.com/comp/cp01.htm|What Computers are Made From]] that has two schematics: a tube NOR gate shown as two triodes with their plates tied together, and a tube NAND gate that is shown as a pentode with the top and bottom grids attached to the inputs. | + | We stated that building an SR latch was a yellow "intermediate" goal, and we're happy to have accomplished this. We did investigate doing other digital logic with vacuum tubes. We found a source called [[http://www.quadibloc.com/comp/cp01.htm|What Computers are Made From]] that has two schematics: a tube NOR gate shown as two triodes with their plates tied together, and a tube NAND gate that is shown as a pentode with the top and bottom grids attached to the inputs. While we purchased a few pentode tubes, we decided to focus on the 12AX7s. In our SPICE file, we began experimenting with making an AND gate out of 12AX7 triodes. Under incredibly specific input conditions, it worked well, but it required precise voltage dividers and would probably be a pain to construct. |
| - | TODO: talk about adder (additron tube) | + | A "gotcha" we encountered when building our mechanical system was trying to fit our circuitry into the box. Our latch worked outside of the box, but when we closed the box it caused one of our outputs to short. It's always a good idea to use removable glue the first time you glue your box together! |
| + | |||
| + | ^ Top View of Our Finished Box ^ | ||
| + | | {{ 2014:img_4258b.jpg?840 }} | | ||
| + | |||
| + | |||
| + | ===== Useful Links ===== | ||
| http://www.ludd.luth.se/~ragge/vtc/ | http://www.ludd.luth.se/~ragge/vtc/ | ||
| http://www.quadibloc.com/comp/cp01.htm | http://www.quadibloc.com/comp/cp01.htm | ||
| http://www.google.com/patents/US2784312 | http://www.google.com/patents/US2784312 | ||
| - | THIS: http://archive.computerhistory.org/resources/text/Knuth_Don_X4100/PDF_index/k-8-pdf/k-8-r5367-1-ENIAC-circuits.pdf | + | http://archive.computerhistory.org/resources/text/Knuth_Don_X4100/PDF_index/k-8-pdf/k-8-r5367-1-ENIAC-circuits.pdf |
| SPICE models from: http://www.duncanamps.com/technical/ltspice.html | SPICE models from: http://www.duncanamps.com/technical/ltspice.html | ||
| - | TODO: WORK PLAN (yellow goal!) | + | |
| - | TODO: AND? OR? | + | |
| - | TODO: Link to ENIAC paper | + | |
2014/vacuum_tube_sr_latch.1418881473.txt.gz · Last modified: 2014/12/18 00:44 by fbourke
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