7 ms·
Constructing an 8-bit relay computer from scratch
- superzamp 6y agoClicked for the sound, was not disappointed.
- bloak 6y agoYes. Also the blinkenlights are very satisfactory. And very nice casing. What is the clock speed at the end of the demo? It sounds like about 8 Hz.
- whatatita 6y agoHe mentions in an earlier video that the fastest speed the closk can run at is 32Hz.
- deleted 6y ago[deleted]
- bencollier49 6y agoThe clicking sound was so pleasing.
- amelius 6y agoCan anyone explain why the contact DC voltage rating of relays is often much lower (5x is no exception) than the AC rating?
- alufers 6y agoI think it is due to arcing. With AC an arc will extinguish itself itself when the voltage goes through 0, but for DC no such thing occurs and an long arc can damage the relay contacts.
- amelius 6y agoYes I figured that, but the 50/60Hz frequency seems quite low for that to be the case.
- Doxin 6y ago50Hz basically means the arc is extinguished after at most 20 milliseconds, limiting how much the contacts heat up. For DC on the other hand there's no guarantee the arc will extinguish at all. You can imagine how a sustained arc would be bad for a relay. Of course a higher frequency would heat the contacts even less, and I imagine you could get a relay rated for even higher voltages given a higher AC frequency.
- amelius 6y agoBut arcs only happen when the contacts are almost-but-not-entirely closed, I suppose (ionization could be a factor). This time-period is, I suppose, very short, much shorter than the 10 milliseconds of the AC half-wave. I suspect the arc could cause the contact to stick for a while, which may increase the arc time.
- deleted 6y ago[deleted]
- Doxin 6y agoAt high enough voltages you get anywhere from second-long to indefinite arcing. Not to mention that the contacts are cost optimized, so the manufacturer would like to get away with as little travel as they can as to simplify the mechanism.
- megous 6y agoI don't think that's a universal effect. https://www.youtube.com/watch?v=-cM8P6-aAf4 https://www.youtube.com/watch?v=-cM8P6-aAf4
- segfaultbuserr 6y ago
- OnACoffeeBreak 6y agoAs the other poster pointed out arcing is one component. Another is that DC voltage equivalent of an AC voltage is the RMS value of the AC signal. So, V_AC_RMS = V_peak / sqrt(2).
- labawi 6y agoAC specifications are usually in RMS equivalent voltage so 1A 10V AC is same power as 1A 10V DC. This makes the peak difference larger, not smaller. AC is easier to extinguish (0A current 100 times / s), and I believe the reversible direction makes for better electroplating characteristics.
- magicpossum 6y agoHaving just finished Charles Petzold's Code book, and reading all about relays and building up a fully working computer solely using relays, it's amazing to see a real physical working relay computer! Incredible work!
- dvh 6y agoCould this kind of computer work at 450°C?
- imglorp 6y agoThat's a great question if you're asking about using it on Venus. Copper melts at 1084 C, so you're good there for springs, conductors and contacts. You'd need insulation for wires and circuit boards: something like fiberglass weave would be good up to 537C. No solder, wire wrap, steel posts. Resistors and capacitors for RC circuits should be similar, carbon is good and capacitors are insulator/conductor layers. I suspect making a temperature controlled oscillator will be very hard. This means power supply AC current might be hard to make. Anyway rebuilding OP's computer that can run in your kitchen oven would be a nice hobby goal. https://www.mcmaster.com/high-temperature-insulation/fiberglass-high-temperature-sleeving/ https://www.mcmaster.com/high-temperature-insulation/fibergl...
- frabert 6y ago> Copper melts at 1084 C, so you're good there for springs Would you really be able to make a spring out of copper? It is my understanding that copper work hardens very quickly, which is a big no-no if you're making a spring, I guess
- imglorp 6y agoTrue, bad idea, anyway there's many metals for that including steel, etc.
- opwieurposiu 6y agoFor springs you have to use Beryllium copper https://en.wikipedia.org/wiki/Beryllium_copper https://en.wikipedia.org/wiki/Beryllium_copper
- swiley 6y agoThe spring constant/youngs modulus probably changes with temperature. Making a relay work reliably over that kind of range sounds difficult.
- curl_e 6y agoSee also TIM a computer made from scrap relays - https://www.youtube.com/watch?v=RfXrT619jBw https://www.youtube.com/watch?v=RfXrT619jBw
- userbinator 6y agoThe architecture looks vaguely similar to a Motorola 68HC12, down to the big-endian encoding. Quite ambitious considering that it has more registers than a 6502. Note that while most people here seem to associate relays with large clicking things, there are reed relays which are much smaller and faster, and also practically silent: https://en.wikipedia.org/wiki/Reed_relay https://en.wikipedia.org/wiki/Reed_relay ...and people have built computers using them: http://www.xpl0.org/rr6/ http://www.xpl0.org/rr6/
- bittercynic 6y agoVery impressive! At the last Vintage Computer Fest West before covid I saw this on display [1] and was completely taken with the clicky sound and blinkenlights. It does use semiconductors for the memory and IO. I built one last March and April, and found it to be surprisingly enjoyable and relaxing. Highly recommended for those who love clicking and blinking things. [1] http://relaysbc.sourceforge.net/ http://relaysbc.sourceforge.net/
- sitkack 6y agoThe author of that board might swing by.
- kpgraham 6y agoIn my senior year of high school (1968-69) Mike Sivy (Yes that Michael Sivy) and I tried to build some components of a digital computer out of military surplus relays. We took the bus and the subway down to Canal Street in NYC and bought a box of large 24 volt relays. We designed a counter and we were able to get some parts working. It took 5 relays for each part, which Sivy was able to drop down to 4 by using a diode. I always thought that the diode was cheating and by using it we lost the purity of the concept, but we had a limited number of relays and we wanted to count to 8. One of our problems was hysteresis and at various times the whole thing would start sparking and chattering like crazy. I remember trying to explain what we did to parents that wandered into the physics lab in the school's open house. They were more impressed with the giant "jabob's ladder" we built that eventually set the lab's window moulding on fire.
- jstanley 6y agoWhat a fantastic machine, amazing work!
- thechao 6y agoRelays were invented in the 1830s. Why were tubes used instead of relays? Do they switch faster?
- detaro 6y agoyes, a lot faster. Mechanical relays will probably be at best <30Hz, tube circuits can do 10000Hz+
- chaoticmass 6y agoIf you like relay computes, you might also like this: https://www.youtube.com/watch?v=_j544ELauus https://www.youtube.com/watch?v=_j544ELauus 1958 FACOM 128B Japanese Relay Computer Sounds really cool when it's running!
- dokem 6y agoI just got into that channel recently. The youtuber was one of the 4 guys that restored the Apollo guidance computer. The entire process is documented on his channel. It was very humbling to watch these guys debug damn near every transistor and logic gate and eventually run the old lunar landing sequence. The also recovered some lost code that was still stored in the core-rope ram from 50 years ago, as well as built gate accurate emulators for the AGC itself and other peripherals. Definitely worth checking out.
- dokem 6y agoI never got why the relays used in old computers were so large. Typically relays are power devices so they are kind of beefy. But for computers of that era I always thought it would be possible to create boards with much higher relay density. We did have quite advanced manufacturing technology at the time. Maybe it really wasn't as much of a concern and transistors and IC came online before it mattered.
- renw0rp 6y agois there BOM available? at least for the of the shelf electronic parts