Relay adder

Zum Beispiel, Mon May 18 2009, 10:26PM

And now for something utterly pointless:

1242684100 514 FT1630 Etupaneeli

At work we had to tear apart a nice big Trane water cooler (200kW+) and I, of course, took everything I could pry off with me. I ended up with a load of nice goodies from it, but the control box for the condenser coil's fans turned out to be the most interesting find. See, it had a boatload of Danfoss CI9 contactors (several kW of power handling, 4kW I think, 3 phase), that were in good condition. I was going to put them all on a shelf for later use, when I remembered a thread on the old (err... older) 4HV forum, where old relay based computers were discussed. Well, seeing how I had got a bucketload of (rather huge) relays, I had to try something myself. A bit of googling brought me to this page, and well, it was all downhill from there, really.

It's pretty much a blatant rip-off of the schematic on that site, but the high power contactors give it a nice little 'earth-quaky' twist tongue The only major difference is that it doesn't have any memory as such, since I didn't have enough relays. But the input switches do the same job (less complex, but not as fun). You flip the switches to the desired binary values and throw the read/write switch, and it spits out an answer (the correct one, I might add). No solid state parts, even the indicator lights are real light bulbs. Logic 1 is 230VAC (phase), 0 is 0VAC (neutral).

This thing ended up costing next to nothing at all, as the relays, or contactors, switches and indicator lights all came from the control box. The front panel was made from some piece of metal that had been lying around for way too long, and the frame didn't cost much either. Hell, even all the wires were salvaged from the control box, which is a good thing, as there are a lot of them. The only major cost of the project were the auxiliary contacts, but even those I got for something like an € a pop from a good electrician friend of mine.

So, here is how I spent a weekend of my life, working on something completely pointless, that just ended up wasting a ton of space (but hey, isn't that what 99% of the projects on here are like?). I named it KYY-1, after the venomous snake (kyy = an adder, ain't I clever).

Here's a view of the contactors:
1242684100 514 FT1630 Kontit

And here's a look at the back of the front panel:
1242684100 514 FT1630 Paneelin Piuhat

Somehow I'm unable to take a decent picture... mistrust

Re: Relay adder
Z28Fistergod, Tue May 19 2009, 02:18AM

I like it! I always wanted to do something like that.
Re: Relay adder
Myke, Tue May 19 2009, 02:33AM

Ooo. Very nice. I always have liked relay logic. I wanted to build a relay computer that does simple arithmetic but I can't seem to find decent relays under $1.
Make it so it has memory and can switch between addition and subtraction. :P
Re: Relay adder
Solidacid, Tue May 19 2009, 06:56AM

Awesome!, now add some more relays and a screen and make it do 3D graphics tongue
Re: Relay adder
Vegemeister, Tue May 19 2009, 07:05AM

How about reed switches? They're cheap, and they're very fast compared to most mechanical switches.
Re: Relay adder
Firnagzen, Tue May 19 2009, 10:30AM

Record us a sound file of it working, please?

Even better: add middling sized capacitors between each wire and the ground so that you add a bit of delay between each 'clunk' of the relays switching.
Re: Relay adder
uzzors2k, Tue May 19 2009, 11:04AM

+1 Geek Cred. cheesey
Re: Relay adder
Proud Mary, Tue May 19 2009, 01:08PM

Golly gosh, what a well-made piece of work!

I would suggest vacuum relays, but even the CCCP ones are FIM 136 each, but less for quantity.

Let me know if you are interested.
Re: Relay adder
Bjørn, Tue May 19 2009, 01:12PM

Make it so it has memory and can switch between addition and subtraction.
You stumbled into the main point, the problem with simple computers is always the memory. The CPU itself can always be made so simple that the memory is 99% or more of the work. A turing complete computer can be made out of a handful of relays/logic gates/transistors, but useful memory will need thousands. My solution is to use dynamic memory and capacitors as the memory elements.


How about reed switches? They're cheap, and they're very fast compared to most mechanical switches.
I have done experiments with that too and I think it is possible to make a computer with a clock in the kHz range. The main problem I had was that they seemed to have a lot of bouncing that will make things a bit more complicated.
Re: Relay adder
Dr. Dark Current, Tue May 19 2009, 06:25PM

Bjørn wrote ...

You stumbled into the main point, the problem with simple computers is always the memory. The CPU itself can always be made so simple that the memory is 99% or more of the work.
Wouldn't something like this do the job? Link2

Re: Relay adder
Sulaiman, Tue May 19 2009, 07:00PM

Every time I see core memory I get upset!

In my youth I had 4k x 8 of Plessey core memory,
never found a use for it so binned it ! cry

One of the things that originally got me interested in electronics (?)
was an exhibit at my local science museum,

relays and lamps and switches with a 6 x 6 chequerboard,
'Fox and hounds' on this machine was fascinating !
Re: Relay adder
Renesis, Tue May 19 2009, 09:32PM

when I remembered a thread on the old (err... older) 4HV forum, where old relay based computers were discussed

I love relay logics. I'd like to try this with pneumatic valves and sylinders, just for the noise and exessive power consumption.

Please, post a film of this computer in action cheesey
Re: Relay adder
Bjørn, Tue May 19 2009, 09:59PM

Wouldn't something like this do the job?
The main problem is that core memory is close to impossible to use without radio tubes or transistors since the signal is very weak.