Relay Computer

Built as something to keep me busy over the Summer holidays from Uni. 168 relays in total with about 25m of wire joining them all up. Requires 12V to operate and draws about 2-3 Amps peak. It is a very basic computer containing an ALU and Memory that has a data width of 4 bits.


2's compliment binary with 4 bits:

0111 = 7
0110 = 6
0101 = 5
0100 = 4
0011 = 3
0010 = 2
0001 = 1
0000 = 0
1111 = -1
1110 = -2
1101 = -3
1100 = -4
1011 = -5
1010 = -6
1001 = -7
1000 = -8


Basic Binary with 4 bits:

1111 = 15
1110 = 14
1101 = 13
1100 = 12
1011 = 11
1010 = 10
1001 = 9
1000 = 8
0111 = 7
0110 = 6
0101 = 5
0100 = 4
0011 = 3
0010 = 2
0001 = 1
0000 = 0


Further information:

CODE by Charles Petzold
ISBN : 0-7356-1131-9
Amazon : http://www.amazon.co.uk/Code-Language-DV-Undefined-Charles-Petzold/dp/0735611...

Harry Porter's Relay Computer
Web : http://web.cecs.pdx.edu/~harry/Relay/
Youtube : http://www.youtube.com/watch?v=n3wPBcmSb2U

JBStanleys Relay CPU
Web : http://www.electronixandmore.com/project/relaycomputertwo/index.html
Youtube : http://www.youtube.com/watch?v=MM4IUxXiArY

Category:

Science & Technology

Tags:

• Relay
• Computer
• Electronics
• Digital
• Binary
• Arithmetic
• Soldering

[AllGs]

I have a question. why were relays never used as a transistor in place of Vacuum tubes? I mean you can do the same operation with them can't you?

[Frogstopper]

@AllGs Yep, they essentially do the same thing but vacuum tubes can do it much faster.

[Nicholas2472]

How do you make the adder take away?

[Frogstopper]

@Nicholas2472 Technically the adder is still adding - it's just adding the negative of what you wanted to subtract :). E.g. a - b = a + -b

Looking at the 2's Compliment binary table, if you take a number, invert all the bits and add 1 you end up with the negative of that number. In the machine the XORs are used to invert all the bits of the B input (@3:00), and then 1 is fed in to the carry in of the adder to get the "add 1" part.

[tvolala1976]

What are those two trapezoidal figures in the schematic at the end?

[Frogstopper]

@tvolala1976 Hey, they're multiplexers (A 4PDT switch in the machine). For the lower one, based on whether the "A/C" input is set, either "Mem" or "A" will be output.

[plavins1]

can it run crysis? where do you connect keyboard to this computer?

[gevidez]

it's a 4-bit ALU

[AllGs]

@Zorbeltuss WOW! How did I miss this? 0_O

This is amazing, I have always wondered why nobody thought of using relays but never actually stumbled on perhaps one of the greatest invention in the history of of computing =\

thanks for the info

[Zorbeltuss]

@AllGs They did, just earlier and on the wrong side of world war 2, Konrad Zuses Z3 was the worlds first functional computer and all relay at that. However it has not been in the limelight because its architechture is so alien from other computers because the lack of development relationship, they only figured it was Turing complete 57 years after it was built, wikipedias article is my recommendation in reading up on it.

[astaroth120]

can it run crysis 2 ?

[dshmechanic]

If Rube Goldberg ever had the opportunity or inclination to cross over into the world of electronics, I'm pretty sure your computer would resemble one of his creations, LOL. Very neat computer, though!!

[anothatech]

That is too very cool

[jamespb89]

All I can thing about is that I want to model this with Minecraft