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Registered Member #514
Joined: Sun Feb 11 2007, 12:27AM
Location: Somewhere in Pirkanmaa, Finland
Posts: 295
And now for something utterly pointless:
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 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).
Registered Member #540
Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969
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
Registered Member #567
Joined: Tue Mar 06 2007, 10:55AM
Location: Singapore
Posts: 147
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.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
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.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
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.
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