Retrotechtacular: New York City’s Secret Computer

Over 750,000 people pass through New York City’s Grand Central Terminal each day. Located in the heart of the city, it’s one of the largest train stations in the world. Its historic significance dates back to 1913, when it opened its doors to the public. At the time, few were aware of the secret computer that sat deep in a sub basement below the hustle and bustle of the city’s busy travelers. Its existence was kept secret all the way into the 1980’s.

Westinghouse had designed a system that would allow authorities to locate a stuck train in a tunnel. There were cords stretched the length of the tunnels. If a train stalled, the operator could reach out and yank on the cord. This would set off an alarm that would alert everyone of the stuck train. The problem being that even though they knew a train was down, they did not know exactly where. And that’s where the computer come in. Westinghouse designed it to calculate where the train was, and write its location on some ticker tape.

So this is the part of the post where we tell you how the computer established where exactly the train breakdown occurred. Although the storyteller in the video is admirably enthusiastic about telling the story, our depth of detail on the engineering that went into this seems nowhere to be found. Let us know in the comments below if you have a source of more information. Or just post your own conjecture on how you would have done it with the early 20th century tech.

The invention of the two way radio made the whole thing obsolete not long after is was built. Never-the-less, it remains intact to this day.

Thanks to [Greg] for the tip!

Update: What You See Is What You Laser Cut

If there’s one thing about laser cutters that makes them a little difficult to use, it’s the fact that it’s hard for a person to interact with them one-on-one without a clunky computer in the middle of everything. Granted, that laser is a little dangerous, but it would be nice if there was a way to use a laser cutter without having to deal with a computer. Luckily, [Anirudh] and team have been working on solving this problem, creating a laser cutter that can interact directly with its user.

The laser cutter is tied to a visual system which watches for a number of cues. As we’ve featured before, this particular laser cutter can “see” pen strokes and will instruct the laser cutter to cut along the pen strokes (once all fingers are away from the cutting area, of course). The update to this system is that now, a user can import a drawing from a smartphone and manipulate it with a set of physical tokens that the camera can watch. One token changes the location of the cut, and the other changes the scale. This extends the functionality of the laser cutter from simply cutting at the location of pen strokes to being able to cut around any user-manipulated image without interacting directly with a computer. Be sure to check out the video after the break for a demonstration of how this works.

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Hackaday Prize Entry: From Q To NAND

The apocalypse is coming, and the last time I checked, not many people have a semiconductor fab in their garage. We’ll need computers after the end of the world, and [matseng]’s project for the Hackaday Prize is just that – a framework to build computers out of discrete components.

The apocalyptic spin on this project is slightly exaggerated, but there is a lot someone can learn by building digital devices out of transistors, resistors, and diodes. The building blocks of [matseng]’s computer are as simple as they come: he’s using three resistors, four diodes, and one NPN transistor to build a single NAND gate. These NAND gates can then be assembled into any form of digital logic. You’re never going to get a better visual example of functional completeness.

A project like this must be approached from both the top down and bottom up. To go from a high level to ones and zeros, [matseng] built an assembler and an emulator. Some ideas of what the instruction set will be are laid out in this project log, and for now [matseng] is going for a Harvard architecture with eight registers. It’s a lot of work for a computer that will be limited by how much memory [matseng] can be wired up, but as far as ambition goes, there aren’t many projects in the Hackaday Prize that can match this tiny, huge computer.

The 2015 Hackaday Prize is sponsored by:

Making Mario Kart Real

If you’ve ever had a casual go-kart experience, you might be able to relate to [HowToLou]. He noticed that whenever he tried to race, the same situation inevitably always happened. One racer would end up in front of the pack, and no one else would be able to pass them. The result was more of a caravan of go-karts than an actual race. That’s when he realized that video games like Mario Kart had already figured out how to fix this problem long ago. [Lou] took ideas from these games and implemented them onto a real life go-kart in order to improve the experience. The result is what he calls a Flash Kart.

The key to improving the experience was to add more features that you don’t normally get in a real word go-karting experience. The Flash Kart uses an electronic drive system that is controlled by computer. This setup allows the computer to limit the speed of the kart so they are all the same. The system includes a Logitech gaming steering wheel with built-in control buttons. There is also a color LCD screen mounted as a heads up display. The screen displays the racer’s speed in miles per hour, as well as multiple MP3 music tracks to choose from. The system provides the user with a limited number of speed boost tokens, listed on the heads up display. The user can also view their current ranking, their location on the track, or even get a view directly behind them.

The back of the kart includes a 23″ LCD screen that shows other players who you are and what team you are on. For added fun, the rider can display taunting messages to other racers using this screen. The front of the kart includes a laser cannon for shooting other karts as well as a “token scoop” sensor. This allows the riders to pick up virtual items such as laser cannon ammo, shields, or extra speed boost tokens.

To pack in all of this added functionality, [Lou] started with a typical go-kart chassis. From there, he built a custom fiber glass shell for the back-end. This houses most of the sensitive electronics. The system is powered by three 12V deep cycle batteries. A 15HP electric motor drives the rear wheels. The throttle is controlled with a gas pedal that simply feeds to a sensor that is hooked up to the control computer. The heart of the system is a computer that runs on a 2.6Ghz small footprint Zotac motherboard with Windows XP. The software is custom written in C#. The computer is plugged into a miniLAB 1008 interface board. This is how it communicates with all of the various sensors. The interface board is also used to control a number of relays which in turn control the speed of the kart.

Unfortunately [Lou] built this kart years ago and doesn’t include many details about what sensors he is using, or how the software works. Still, this was such a cool idea that we had to share it. Be sure to watch [Lou’s] video below to see the kart in action. Continue reading “Making Mario Kart Real”

Discrete Transistor Computer Is Not Discreet

Every few years, we hear about someone building a computer from first principles. This doesn’t mean getting a 6502 or Z80, wiring it up, and running BASIC. I’m talking about builds from the ground up, starting with logic chips or even just transistors.

[James Newman]’s 16-bit CPU built from transistors is something he’s been working on for a little under a year now, and it’s shaping up to be one of the most impressive computer builds since the days of Cray and Control Data Corporation.

The 10,000 foot view of this computer is a machine with a 16-bit data bus, a 16-bit address bus, all built out of individual circuit boards containing single OR, AND, XOR gates, decoders, multiplexers, and registers.  These modules are laid out on 2×1.5 meter frames, each of them containing a schematic of the computer printed out with a plotter. The individual circuit modules sit right on top of this schematic, and if you have enough time on your hands, you can trace out every signal in this computer.

The architecture of the computer is more or less the same as any 16-bit processor. Three are four general purpose registers, a 16 bit program counter, a stack pointer, and a status register. [James] already has an assembler and simulator, and the instruction set is more or less what you would expect from a basic microprocessor, although this thing does have division and multiplication instructions.

The first three ‘frames’ of this computer, containing the general purpose registers, the state and status registers, and the ALU, are already complete. Those circuits are mounted on towering frames made of aluminum extrusion. [James] already has 32 bytes of memory wired up, with each individual bit having its own LED. This RAM display will be used for the Game of Life simulation once everything is working.

While this build may seem utterly impractical, it’s not too different from a few notable and historical computers. The fastest computer in the world from 1964 to ’69 was built from individual transistors, and had even wider busses and more registers. The CDC6600 was capable of running at around 10MHz, many times faster than the estimated maximum speed of [James]’ computer – 25kHz. Still, building a computer on this scale is an amazing accomplishment, and something we can’t wait to see running the Game of Life.

Thanks [aleksclark], [Michael], and [wulfman] for sending this in.

Vintage Computers At Maker Faire

It’s no secret that Maker Faire is highly geared toward the younger crowd. This doen’t mean the Faire is completely devoid of the historic; the Bay Area Maker Faire is right in the heart of the beginnings of the computer industry, and a few of the booths are showing off exactly how far computers have come over the last forty years.

Superboard[Vince Briel] of Briel Computers has a booth showing off his wares, mostly modern reimaginings of vintage computers. His table is loaded up with replica 1s, a board that’s much smaller but still completely compatible with the Apple I. The MicroKIM made an appearance, but the crown jewel is [Vince]’s Superboard III, a replica of the Ohio Scientific Superboard II. It’s your basic 6502 computer with 32k of RAM, but unlike just about every other modern retrocomputer out there, [Vince] put the keyboard right on the main board.

The switches are Cherry MX, the keys are from WASDkeyboards. [Vince] is actually getting a lot of interest in making modern ASCII keyboards to replace the old and busted boards that came in the home computers of the 70s and 80s. That might be a project [Vince] will release sometime in the future.

[Jef Raskin], the Swift Card, and the Canon Cat

[Steve Jobs] may have been the father of the Macintosh, but he was, by no means, solely responsible for the Mac. It was a team of people, and when you talk about the UI of the Mac, the first name that should come up is [Jef Raskin].

One of [Jef Raskin]’s finest works was the Swyft Card, an add-on to the Apple II that was basically just a ROM card that had an OS and Forth interpreter on it. The distinguishing feature of the Swyft card was the use of ‘leap’ keys, a simple way to change contexts when using the computer. We’ve seen replicas of the Swyft card before, courtesy of [Mike Willegal] at the Vintage Computing Festival East.

Woodie[Dwight Elvey] of the forum brought a few extra special items related to [Raskin] and the Canon Cat. The first was a Swyft card installed in an Apple IIe. The second was a prototype Swyft computer, with SERIAL NUMBER 1 printed on a Dymo label and fixed to the case.

The ‘woodie’, as [Dwight] calls it, has two 1.44 MB disk drives, of which half of the disk is actually usable. [Dwight] didn’t take the machine apart, but I’m 99% sure the CRT in it is the exact same tube found in early 9″ Macs.

Also in [Dwight]’s display is a production Swyft computer and a Canon Cat, the final iteration of [Jef Raskin]’s idea of what a text-based computer should be.

The vintage-computer booth also had a few interesting retrocomputers including a Commodore 128D, the Apple made, Bell & Howell branded Apple II, and an Amiga 2000. Right next door was the Computer History Museum, who brought a very kid-friendly storage medium display. Showing a 10-year-old an 8″ disk is fun.

Relays Calculate Square Roots

After seeing an exhibit of an old relay-based computer as a kid, [Simon] was inspired to build a simple two-relay latching circuit. Since then, he’s been fascinated by how relays can function to do computation. He’s come quite a long way from that first latching circuit, however, and recently finished a huge five-year project which uses electromechanical relays to calculate square roots.


The frame of the square root calculator can hold up to 30 identical relay modules, each of which hold 16 relays on PCBs, for a total of 480 relays. The module-based setup makes repair and maintenance a breeze. Numbers are entered into the computer by a rotary dial from an old phone and stored in the calculator’s relay memory. A nixie tube display completes the bygone era-theme of the device and shows either the current number that’s being entered, or the square root of that number as it’s being calculated.

The real magic of this project is that each relay has an LED which illuminates whenever the relay is energized, which shows the user exactly where all of the bits of the machine are going. [Simon] worked on this project from 2009 and recently completed it in 2014, and it has been featured at the San Mateo Maker Faire and at Microsoft Research in Redmond, WA. We’ve seen smaller versions of this before, but never on this scale and never for one specific operation like square roots.

Video below. Thanks to [Bonsaichop] for the tip!

Continue reading “Relays Calculate Square Roots”