Lego Logic Gates

Thud457 writes "LEGO Logic Gates - It's like Babbage, but with bricks. All the gates except XOR are here, and he goes on to develop a clocked flip-flop. While practical mechanical computers may be out, even at the nanotechnological scale, nanomechanical memory may be in. "

Comments

No need for XOR

[Anonymous Coward]

XOR can be constructed by combining other gates. You acctually just need NAND-gates to be able to create any other gate or larger structure.

Re:No need for XOR

[ricotest]

However, while NAND is the cheapest gate to make with silicon, it's quite a hefty Lego structure. So alternatives would be more desirable.

Re:No need for XOR

[ScriptMonkey]

If you are using static complementary CMOS logic, nands are cheaper. If you happen to be using an older logic family like NMOS or RTL logic, nor gates are cheaper. In any logic family, xor gates are quite a bit more complex than either.

Re:No need for XOR

[Anonymous Coward]

iirc in TTL nand was significantly cheaper due to the ability to use double base transistors

i don't think it ever made much difference in mos technology

in cmos the only difference between a nand and a nor is the P and N are the other way roung

This was just plain mean

[Anonymous Coward]

From the (now Slashdotted) page accessed via MirrorDot:

Before you read on, if you have had trouble accessing this page then please accept my apologies. The previous bandwidth issues should be solved now that I have a new server.

Re:This was just plain mean

[MrNonchalant]

MirrorDot appears to be down at the moment. In the meantime I mirrored it here. Unfortunately my web host isn't that generous so I'll probably take it down very shortly. Those that want to mirror the mirror can grab a zip file copy here

Re:Mechanical Analogs

[Viol8]

I guess the best use of mechanical digital circuits would be if you don't care about speed but want something almost indestructable. Build the cogs out of titanium with teflon coating for lubrication and who knows what the possibilities could be. Just think of the dangerous places you could send a robot built out of this stuff. Output could be an issue though unless you have the thing wave little semaphore flags and some guy with binoculars notes them down!

Re:Mechanical Analogs

[Ford Prefect]

There may be no obvious immediate use for mechanical analogs of digital circuits, when digital circuits are orders of maginitude faster than mechanical circuits

If you scale things down a bit, mechanical 'circuits' can become a lot faster - and combined with the electrical properties of the components there might be an interesting hybrid some point in the future.

Still, using Lego is just a little insane, and there is the minor problem of a '1' or a '0' slowly degrading into '0.5's further along the Lego logic chain... :-)

Re:OT: Question for Slashdotters

[a24061]

If you mean software to simulate building digital circuits out of gates, look at TKGate.

Re:WOW

[Ashtead]

I'd say that depends on the particular kind of logic circuit. DTL and original TTL were natural for NAND-functions, just add another emitter in the input stage for TTL, or equivalently, another diode for DTL to add more inputs. A one-input gate would be the NOT gate. NOR-functions would be achieved by parallelling transistors in the second stage of the gate, hence adding another input then meant adding an another entire input stage also. This would be more space-consuming an thus more expensive.

For ECL, the situation is the opposite, since here everything is mostly transistor stages connected in parallel, as well as generally available true and complementary outputs, so the NOR or OR functions are the most common. Add another transistor in parallel for each additional input, and outputs can be tied together in some cases, forming more OR-functionality. With inversions, the necessary AND and NAND functions may be generated as per DeMorgans theorem.

The situation for NMOS, PMOS and RTL are similar to the one for ECL: transistors in parallel for the basic NOR function are generally preferred to transistors in series for the NAND function.

In CMOS circuits, NAND and NOR are about the same in complexity, it is a matter of parallel-connecting the P-channel transistors and series-connecting the N-channel transistors for a NAND function, and vice versa for the NOR function.

Here is some information about the internal connections of RTL, DTL, TTL, ECL and CMOS circuits.

Re:A couple problems.

[RPI Geek]

Giving the gates gain may be possible, too, but it would require powering each gate, either with electrical power or some sort of funky mechanical setup.

When I read the title of this article, I tried coming up with a design in my head of how I would do this, and my idea is to make the clock pulse out of a rotating shaft with cams (easy enough for Lego pieces). The cams are what would actually power the pieces, thereby eliminating the effects of backlash and fanning. The only problem comes with a lack of torque, but it would be easy to simply tie in more motors (or more hand-cranks) to get more power down the line. I think that this is a more elegant solution than having a person manually slide a shaft back and forth for the clock pulses.

It's a fair cop...

[Thud457]

Yeah, I was being a jackass and seeing if the editurs were awake.

It's still cool though.

Re:cool

[Kehvarl]

The trick would be programming it. You'd need some way of storing information. My thinking would be to use a chain with links denoting one and zero. Then you'd just need a mechanism to read and write the chain.

I have just two words for you.
Paper.
Tape.

Re:This is sort of cool, but...

[LanceUppercut]

Ternary "Setun" machines developed in Moscow State University in the 50's are well-known examples of non-binary computers.