Constructing an 8-bit relay computer from scratch

#1

Post by hggh » Wed, Jan 20, 2021, 10:23 AM UTC

Constructing an 8-bit relay computer from scratch
relaycomputer.co.uk

Re: Constructing an 8-bit relay computer from scratch

#2

Post by superzamp » Fri, Jan 22, 2021, 10:49 AM UTC

Clicked for the sound, was not disappointed.

Re: Constructing an 8-bit relay computer from scratch

#3

Post by amelius » Fri, Jan 22, 2021, 11:02 AM UTC

Can anyone explain why the contact DC voltage rating of relays is often much lower (5x is no exception) than the AC rating?

Re: Constructing an 8-bit relay computer from scratch

#4

Post by alufers » Fri, Jan 22, 2021, 11:13 AM UTC

amelius wrote: post #3

Can anyone explain why the contact DC voltage rating of relays is often much lower (5x is no exception) than the AC rating?

I think it is due to arcing. With AC an arc will extinguish itself itself when the voltage goes through 0, but for DC no such thing occurs and an long arc can damage the relay contacts.

Re: Constructing an 8-bit relay computer from scratch

#5

Post by amelius » Fri, Jan 22, 2021, 11:32 AM UTC

alufers wrote: post #4

amelius wrote: post #3

Can anyone explain why the contact DC voltage rating of relays is often much lower (5x is no exception) than the AC rating?

I think it is due to arcing. With AC an arc will extinguish itself itself when the voltage goes through 0, but for DC no such thing occurs and an long arc can damage the relay contacts.

Yes I figured that, but the 50/60Hz frequency seems quite low for that to be the case.

Re: Constructing an 8-bit relay computer from scratch

#6

Post by bloak » Fri, Jan 22, 2021, 11:38 AM UTC

superzamp wrote: post #2

Clicked for the sound, was not disappointed.

Yes. Also the blinkenlights are very satisfactory. And very nice casing.

What is the clock speed at the end of the demo? It sounds like about 8 Hz.

Re: Constructing an 8-bit relay computer from scratch

#7

Post by magicpossum » Fri, Jan 22, 2021, 11:42 AM UTC

Having just finished Charles Petzold's Code book, and reading all about relays and building up a fully working computer solely using relays, it's amazing to see a real physical working relay computer! Incredible work!

Re: Constructing an 8-bit relay computer from scratch

#8

Post by OnACoffeeBreak » Fri, Jan 22, 2021, 12:09 PM UTC

amelius wrote: post #3

Can anyone explain why the contact DC voltage rating of relays is often much lower (5x is no exception) than the AC rating?

As the other poster pointed out arcing is one component. Another is that DC voltage equivalent of an AC voltage is the RMS value of the AC signal. So, V_AC_RMS = V_peak / sqrt(2).

Re: Constructing an 8-bit relay computer from scratch

#9

Post by dvh » Fri, Jan 22, 2021, 12:19 PM UTC

Could this kind of computer work at 450°C?

Re: Constructing an 8-bit relay computer from scratch

#10

Post by bencollier49 » Fri, Jan 22, 2021, 12:44 PM UTC

superzamp wrote: post #2

Clicked for the sound, was not disappointed.

The clicking sound was so pleasing.