Modern Relay Computers Around the World
There are many hardware hackers besides myself who are exploring the wonderfully clicky world of relay-logic computing. This page aims to collect all modern relay computers into one place, for your viewing pleasure.
The ordering here is mostly arbitrary. The grouping is into three different categories. Many modern computers descend in design from an extremely influential design by Harry Porter; these are collected in the first section. The middle section collects the many other relay computers. The final section contains "honorable mentions"—projects that use relay-logic, but do not aim for Turing-completeness.
If I haven't noticed your project, please contact me to be included in this list. (Must have at least some actual hardware built and do some computations with relays.) Please also contact me for any corrections / additional information, or copyright concerns[1].
Relay Computers Based on Harry Porter's Design
Harry Porter's Relay Computer[2]
| Author: | Harry H. Porter III |
|---|---|
| Relays: | 415 (1411?[3]) |
| Voltages: | 12V |
Large, influential computer with hand-wired relays in the style of the first relay computers. 32 KiB static RAM, but appears to be pure relay-logic otherwise.
DiPDoT Relay Computer
| Author: | "DiPDoT" |
|---|---|
| Relays: | 415 (?) |
| Voltages: | 5V |
A relay computer by user 'DiPDoT', based on Harry Porter's Relay Computer, but implemented with custom PCBs, mostly updating on YouTube.
RC-3 Relay Computer
| Author: | Phil Ryals, Museum of Computer Culture[4], and others |
|---|---|
| Relays: | 418 |
| Voltages: | 12V (?) |
Inspired by Harry Porter's relay computer, comes with lots of documentation.
Carl Hasbargen's Relay Computer / RC-C
| Author: | Carl Hasbargen |
|---|---|
| Relays: | 413 |
| Voltages: | 12V |
Based on Harry Porter's relay computer with a different build and additional features. Carl provided a writeup, which is hosted here!
DAVIAC
| Author: | David Warren |
|---|---|
| Relays: | 416 (+484 per RAM board) |
| Voltages: | 12V |
Clearly inspired by Harry Porter's computer. Multiple relay sizes, with a good build quality. Makes delightful (1) rhythm (2)!
Zusie
| Author: | Fredrik Andersson |
|---|---|
| Relays: | 268[5] |
| Voltages: |
Inspired by Zuse's computers. Cites Harry Porter's computer as inspirational, and the architecture is very similar.
@ClicketyClack on YouTube
| Author: | @ClicketyClack |
|---|---|
| Voltages: | 5V |
Building a relay computer based on PCBs, possibly descended from Porter's computer. Got very far, but either defunct or on extended hiatus.
Other Relay Computers
Mr. Clicky-Clack
| Author: | Agatha Mallett |
|---|---|
| Relays: | ≈300 |
| Voltages: | +12V (relays), +4V (LEDs), +3.3V (electronics) |
Mr. Clicky-Clack is my (Agatha's) project to create an 8-bit relay-logic CPU. See project page for more info!
MERCIA Relay Computer
| Author: | Jeroen Brinkman |
|---|---|
| Relays: | ≈2000 |
| Voltages: | 12V |
A huge relay computer, with solid engineering and many useful notes, such as these for relay-logic!
R 500 / 7 T Relay Computer
| Author: | Jürgen Keller |
|---|---|
| Relays: | ≈500 |
| Voltages: | 24V |
Heavy clicking, good build, useful demo calculating the day of the week of a date. The name is supposed to indicate it is made from about 500 relays, executes 7 instructions per second, and is easily transportable.
Single Board Relay Computer / Relay Trainer
| Author: | Joe Hallen |
|---|---|
| Relays: | 83 |
| Voltages: | 12V |
Mostly a relay-logic ALU driven by a conventional microcontroller; the core is implemented with relays, but all registers except the PC and some control logic are in silicon. Good peripherals and controls. Influential D-flip-flop[6]) design has been widely copied.
Relay Computer Two[7]
| Author: | Jonathan B. Stanley |
|---|---|
| Relays: | 281 |
| Voltages: | 12V |
Full 8-bit CPU. Loosely inspired by Harry Porter's relay computer, but significantly different. Good descriptions of relay-logic gates. Also sells generic relay-logic modules.
"High Performance" Relay Computer[8]
| Author: | Peter Prikasky |
|---|---|
| Relays: | 100 (?) |
| Voltages: | 24V (?) |
16-bit architecture with SPDT relays. Indeed, very fast, and capable of some fairly significant calculations!
Kilian Leonhardt's Relay Computing Projects
| Author: | Kilian Leonhardt |
|---|---|
| Relays: | >1500, 15 (?), 171 |
Main project is a large student project with over 1500 relays, inspired by the Z3. There were also some follow-ons: a 3-bit adder (apparently 15 relays), and then two copies of a larger computer (171 relays). The computers are apparently on display at universities.
A fistful of relays
| Author: | Pavel Dovgalyuk |
|---|---|
| Voltages: | 24V |
A large wired computer. Architecture seems related to Porter's but perhaps not based on it. Shows division and artsy light patterns!
The Embroidered Computer
| Author: | Ebru Kurbak, Irene Posch, and others |
|---|---|
| Relays: | 369 |
8-bit relay computer with 1-bit ALU implemented by embroidered conductive wire and magnetic beads as an art project! See also.
RISC Relay CPU
| Author: | Roel J. H. |
|---|---|
| Relays: | 327 |
| Voltages: | 24V |
Partially completed (but still functional) ambitious relay computer.
Relay CPU
| Author: | Tim |
|---|
Little is known about this janky build, with 12-bit program counter, sequencer, ALU, and semiconductor ROM.
BrainfuckPC Relay Computer
| Author: | Artem Kashkanov |
|---|---|
| Relays: | 567: 439+64+64 relays of different forms |
| Voltages: | 5V (?) |
16-bit relay-logic computer that runs Brainfuck++ instructions. Made out of 439+64+64 Soviet reed relays, with 128 KiB RAM IC.
R200 Relay Computer
| Author: | Alexander Blk |
|---|---|
| Relays: | 44 (?) (out of a planned ≈200) |
| Voltages: | 48V |
No ICs. Project seems to be abandoned.
DVQ Group Relay Computer
| Author: | DVQ Group |
|---|---|
| Voltages: | 4.5V (?)[9] |
Work-in-progress computer with nice build. Z80-like architecture, with 8-bit data / 16-bit address.
Relay and Crystal Computer
| Author: | Stephen W. Frey |
|---|---|
| Relays: | 198 |
Modified Harvard architecture, 8-bit instruction bus
RR6: The Reed Relay 6-bit Computer
| Author: | Loren Blaney |
|---|---|
| Relays: | 216 total: 112 DPST reed relays, 104 DPDT relays |
| Voltages: | 5V and 9V |
Harvard architecture, 6-bit registers, PROM implemented with DIP switches. Relays are based on 5V, but are sometimes used with coils in series, resulting in 9V being needed for some circuits. Good writeup.
TIM8: TIM-Series Relay Computing
| Author: | Rory Mangles |
|---|---|
| Relays: | 152 |
| Voltages: | 12V |
Evolving relay computer project. SPDT relays, ingenious RAM solution! See also TIMs 1–7
Duo 14 Premium
| Author: | Jack Eisenmann |
|---|---|
| Relays: | ≈50 (?) |
| Voltages: | 3V (?), 6V (?) |
2-bit relay computer, with 48 bits of ROM and 14 bits of RAM.
i2 8-Bit Relay Computer
| Author: | Taylor |
|---|---|
| Relays: | >300 |
| Voltages: | 6V |
Draws elements from RC-1, RC-3, and Zusie, and is "very similar to" RC2. Progress on nixie tube display! Apparently abandoned.
Relay Computer
| Author: | Paul Kocyla |
|---|---|
| Voltages: | +24V |
A project to make a relay computer with no diodes. Project appears abandoned.
Super Micro Relay Computer
| Author: | Stefano |
|---|---|
| Relays: | 46 |
| Voltages: | 12V |
4PDT relays, design optimized for simplicity.
Daniel Fremont's Relay Computer
| Author: | Daniel Fremont |
|---|---|
| Relays: | 200 (?) |
| Voltages: | 5V |
Inspired by Harry Porter's computer, but seems different. Apparently abandoned despite being "nearly complete"?
Honorable Mentions (Non-Computer Relay-Logic)
Relay-Based Floating-Point Square-Root Calculator
| Author: | Simon A. J. Winder, Matthew Richter |
|---|---|
| Relays: | 480 |
Impressive device that computes floating-point square-roots digit-by-digit, and displays the result on nixie tubes!
Usagi Electric Relay Calculators
| Author: | David Lovett |
|---|
Electronics YouTube channel, with a series on making what appears to be a calculator-style adder in pure relay logic.
Calc-U-Lator
| Author: | Michal Zalewski |
|---|---|
| Relays: | 54 |
| Voltages: | 5V (?) |
Relay-logic calculator, with a nice, retro-inspired build. Runs off a microcontroller, with an adder and segment display implemented with relays.
A Balanced Ternary Adder Built from Relays
| Author: | Jeroen Brinkman |
|---|---|
| Relays: | 37 |
| Voltages: | ±5 V |
A 4-trit (balanced ternary!) relay adder. Built by using 'double-pole triple-throw' relays, themselves made from ordinary relays.
Will Dana's Relay Computer
| Author: | Will Dana |
|---|---|
| Relays: | 61 |
| Voltages: | 5V |
Adder / subtractor, built on proto-boards.
Basic Relay Computer
| Author: | Jonathan B. Stanley |
|---|---|
| Relays: | 19 (?) |
| Voltages: | 12V |
A 4-bit adder with attached registers.
Robin Patenall's Relay Computing
| Author: | Robin Patenall |
|---|---|
| Relays: | 12 / 24 |
| Voltages: | 5V |
A project to build a relay computer, but apparently abandoned in the very early stages.
Back to Relay Logic + Computing.
Back to Electronics Projects.
Notes
See also: