Building a computer from relays.....?

[delorean700]

I would like to figure out how to build a computer out of like relays.

Like the old kinds that read the punch cards and have the lights on them. And you put the punch card in that reads the math problem like 1 + 1 and the lights turn on and off and you write down the binary code (on 1 off 0) then when it is finally done computing you do the binary math to figure out that the answer is 2!

But how would I go about doing this? I need stuff like how many relays I would need and things like that. Does anyone have a guide on this?

I need someone with experience in this field.

Thanks,

Delorean700

[Flamed_Chip]

Wouldn't it be a bit easier to use logic gates instead of just relays. You only need NAND gates to make every other kind of gate thanks to shaffers law.

[delorean700]

Hm I am not sure about that, I just want to do whatever is easiest and cheapest, I don't have a very large budget.

[subtotal]

i think you mean NOT gates

[Flamed_Chip]

No, I mean NAND gates, all other gates can be built using only NAND gates. You can't build an AND gate using NOTs, but you can build one using NANDs. Its shaffers law. You can do the same with NOR gates too I beleive. Boolean Algebra.

[delorean700]

Wouldn't I only need NOT, AND and OR gates that I can create from relays? I could hook those physical gates together using some logic diagrams and create a physical 8-bit ripple-carry adder. Use simple switches to apply inputs to the adder and hook the output lines to lightbulbs or LED's for lower voltages. Then I would be able to read the binary results on the lights.

[subtotal]

No, I mean NAND gates, all other gates can be built using only NAND gates. You can't build an AND gate using NOTs, but you can build one using NANDs. Its shaffers law. You can do the same with NOR gates too I beleive. Boolean Algebra.

actually NAND/NOR gates are made from NOT gates, as a NOT gate is really just a transistor, basicallt an AND gate is two NOT gates in series with independant inputs, and a NOT gate to change a 2 transistor NAND gate into a 3 transistor AND gate

[delorean700]

How many relays does it take to make an OR gate? Im thinking one.

[SavageBasher]

yeah, if you don't want back voltage you'll have to use diodes with both lines.

[delorean700]

Yeah thats a good idea since I would rather burn out a diode instead of a relay. But before I start planning this I need to know how many relays, switches, diodes, batteries, and LED's I would need.

[subtotal]

i apologise for any threadjack as you clearly mean to build this from relays, but i felt i had to clear up a certain misconception concerning logic gates

[delorean700]

Well it depends though, I would use transistors, but I need to find out which is cheaper and easier to make a physical gate out of, relays or transistors.

[mrw8419]

How bout you try to build an electro mechanical pong game like this guy.

LINK (http://www.cyberniklas.de/pongmechanik/video.html)

Michael

[delorean700]

Thats cool, but it doesn't really interest me. I need to find out how to wire relays, switches, LED's and diodes. Along with the cost of each item. I have a pretty good understanding of the gates that I need NOT, AND, and OR.

[delorean700]

bump

[deRusett]

http://www.goldmine-elec-products.com/products.asp?dept=1005

you will want this page

you will notice, relays trasistors, diodes all are around 1-2 dollars each so you can mix and match to make the cheapest possible after you have done the paper work

http://www.keelynet.com/sources/schema1.htm this page is also useful for projects, though some of the links have started to disappear, might be wise to spider the site incase it gets taken down

[delorean700]

Nice webpages, I might buy the stuff from the top one, but the lower one doesn't really help me much, Ive noticed most of the links don't work like you said. I need a schematic for building an adder from relays.

[delorean700]

bump

[carlao2005]

Hello Delorean (reminds me a film that I liked much, "back to the future"... :-)

I have found what you were looking for. I hope you are already interested.

Download the book "how computers work", on the following page:

http://www.fastchip.net/howcomputerswork/p1.html

I have the same plan that you, to build a simple computer. I am a computer science professor, and want to build something simple and didactic, to show students.

If your are already interested, we could exchange information on this work. I am searching for information on how to build a simple relay at home. Is it possible?
I have contacted the author and others on this matter, I could exchange information with you if this interest you.

Best regards!
Carlos

[carlao2005]

Wouldn't I only need NOT, AND and OR gates that I can create from relays? I could hook those physical gates together using some logic diagrams and create a physical 8-bit ripple-carry adder. Use simple switches to apply inputs to the adder and hook the output lines to lightbulbs or LED's for lower voltages. Then I would be able to read the binary results on the lights.
the book shows just it!!
and many things more!!
Carlos again