The Computer Without A CPU

1bit

[Jeff Laughton] was contacted by a customer that was interested in adding some automated functions to a printing press. Before eventually settling on a microcontroller for the job, [Jeff] went old school and started looking at logic gates, counters, and flip-flops. This lead him to the Motorola 14500 industrial control unit, a minimal processor with only 16 instructions. After a few ‘back of the napkin’ sketches, he came up with an extremely minimal computer that doesn’t use a microprocessor. It’s an interesting design notable not only for its electronic brevity, but also because it only uses one instruction.

The only instruction this computer will ever execute is an input test, the result of which controls a two-way branch. Instructions consist of an input address, output address, and a single bit of data. If the data bit is true, the computer jumps to one location in ROM, and if the data bit is false, a jump to another location is executed.

A computer really isn’t a computer without some form of memory, and this design is no exception. [Jeff] managed to add two bits of data between the 8-bit latch and 8-bit multiplexer in the design. This is enough to call a few subroutines which test the I/O-mapped memory to decide what the next instruction should be.

It’s a truly bizarre design, but actually much closer to a true Turing machine than the computers in your pocket, on your wrist, on your desk, and in your car.

Thanks [James] for the tip!

 

Turbot is a Beam/Picaxe Hybrid

BeamBot

[James] wanted to build a BEAM turbot. He ran into some problems with the BEAM circuitry though, and ended up with a BEAM/Picaxe hybrid.
Beam robotics are the brainchild of Mark Tilden. The acronym stands for Biology, Electronics, Aesthetics, and Mechanics. BEAM based bots were very popular with hobbyists in the 90’s and early 2000’s, but popularity has since died down. BEAM robots tend not to use microcontrollers, instead attempting to simplify things down to the lowest number of elements.

[James’] turbot uses a miller solar engine. The original design used the engine to drive a Solar Turbot Latch. [James’] problem was that the photodiode “eyes” of the robot were not properly enabling the 74AC245 to pass current to the motor. Since the robot was built in a tiny space, debugging the circuit was extremely hard. After struggling with the ‘245 for some time, [James] decided to swich out the BEAM circuit for a Picaxe microcontroller.

The Picaxe can only sink or source about 20ma per pin, which is slightly less than the no load current of [James’] motors. To make up for this, he ganged up four pins per motor. There was some risk in the motors blowing up the Picaxe. However between the lightly loaded gearmotors and low current solar panels it seems to be working just fine.  Overall the bot is a very clean, compact build. Jump past the break to check out its really smooth crablike walking action.

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Building a Turing Machine from Magic the Gathering

If you really know your Magic the Gather and you’re a programming wiz you’ll appreciate this paper on building a functioning Turing Machine from Magic the Gathering cards. We’re sure you’re familiar with Turing Machines, which uses a rewritable strip to store and recall data. Most of the time we see these machines built as… machines. For instance, this dry-erase marker Turing Machine has long been on the top of our favorites list. But as The Diamond Age by Neal Stephenson illustrates, there’s more than one way to skin this cat.

A complete list of the cards used in this machine can be found here. A little bit of preparation (casting to tweak abilities) goes into making sure the cards will work as called for in the Turing design. The tape is made of Ally tokens to the right of the head, and Zombie tokens to the left. The computational abilities of the head depend on the colors of the cards. It’s a bit too complex to paraphrase, but the design is based on this 2-state, 3-symbol setup whose rules are listed in the image above.

It’s going to take us a while to fully wrap our heads around this thing, but it’ll be fun getting to that point!

[via Slashdot]

A LEGO Turing machine for [Alan]‘s centennial

2012 is the 100-year anniversary of [Alan Turing]‘s birth, and to celebrate the centennial, [Jeroen] and [Davy] over at Centrum Wiskunde & Informatica in The Netherlands built a Turing machine out of LEGO.

A Turing machine is an extremely simple device, but is still able to compute everything your desktop can. The machine is generally described as an infinite paper tape with a read/write head. On this paper tape, the numbers ‘1’ and ‘0’ are written. By precisely defining what the Turing machine should do when it comes across a ‘1’ or ‘0’, its able to do the same calculations as a laptop, albeit at a much slower rate.

The LEGO Turing machine has a series of pins signifying each bit. These pins are moved underneath a read/write head containing a light sensor and robotic arm. When a pin is down, the camera sees a dark spot signifying one state. When the pin is up, light reflects off a white LEGO piece signifying another state.

[Jeroen] and [Davy] built an IDE for their Turing machine, so if you’ve got a few LEGO NTX bricks lying around you can grab the Git and build your own. Check out the mini documentary after the break.

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Turing machine a masterpiece of craftsmanship

Everything about this Turing machine is absolutely brilliant. A Turing machine uses a strip of material to record, calculate, and change data. [Mike Davey] built this one using servo motors, a Parallax Propeller, felt-tipped pen, and 1000 feet of film leader. The machine writes characters to the leader, reads them using a grayscale camera, and erases them with a rotating felt cylinder.

Watch the video after the break, it covers every one of the intricate details that add up to [Mike's] perfect build. We loved his Nickel-O-Matic but he really outdid himself with this one. With our mouths still agape we’re going back for our fifth viewing.

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