SANAA
UREMBO NA USTAWI
UJANJA
UTAMADUNI NA HISTORIA
BURUDANI
MAZINGIRA
CHAKULA NA VINYWAJI
UHANDISI WA KINYUME
SAYANSI
MICHEZO
TEKNOLOJIA
VAZI
Logic Gates from Relays
Capvideo (Wikimedia Commons) · CC BY 4.0
Ed

Imeundwa na

Ed

27. Agosti 2026FI
38
0
0
0
0

Logic Gates from Relays

A relay is a switch operated by an electromagnet, invented to repeat telegraph signals over long lines and already in this catalogue for that purpose. It has one property its inventors had no reason to care about: because a relay is a switch that ELECTRICITY operates, the output of one relay can operate the next. That is the whole of digital logic. Claude Shannon noticed in 1937, in a master’s thesis usually called the most important of the century, that a network of such switches behaves exactly like Boolean algebra — series contacts are AND, parallel contacts are OR, and a normally-closed contact is NOT. Suddenly a body of mathematics from 1854 became a design method for circuits, and circuit design stopped being intuition and became algebra you could simplify on paper before touching a soldering iron.
Kati
5 hours 30 minutes

Maagizo

1

Start from the telegraph relay

Build or re-read the relay first. It was invented to solve a completely different problem — a telegraph signal too weak to travel further, restored by using it to operate a local switch on a fresh battery.

Note the property that matters here and mattered not at all to its inventors: the thing that operates the switch is the same KIND of thing the switch controls. A lever needs a hand; a relay needs only another relay. That closure under composition is what makes logic possible, and it was sitting unused in telegraph offices for eighty years.

2

Wire AND, OR and NOT from contacts

Three circuits, and every digital device ever built is made of them.

  1. AND: wire two relay contacts in SERIES between supply and lamp. The lamp lights only if both coils are energised.
  2. OR: wire two contacts in PARALLEL. The lamp lights if either coil is energised.
  3. NOT: use a normally-CLOSED contact. The lamp lights when the coil is NOT energised.
  4. Build all three and fill in a truth table for each by trying every input combination.

Series is AND, parallel is OR, normally-closed is NOT. That is Shannon's entire correspondence, and it is worth pausing on how unreasonable it is that a topology of wires should match an algebra of propositions.

Now the payoff: because it IS algebra, you can simplify circuits symbolically. De Morgan's laws say NOT(A AND B) equals NOT A OR NOT B — which means the same function can be built two different ways, and you pick whichever needs fewer contacts. Engineers had been optimising relay circuits by intuition; after 1937 they optimised them by algebra.

Vifaa kwa hatua hii:

ReleiRelei4 vipande
Seti ya taa za LED za kuashiriaSeti ya taa za LED za kuashiria1 seti
Seti ya vizuizi vya umemeSeti ya vizuizi vya umeme1 kifaa
Ubao wa Kutobolewa / Ubao wa MfanoUbao wa Kutobolewa / Ubao wa Mfano1 kipande
Waya wa kuunganishiaWaya wa kuunganishia1 reel

Zana zinazohitajika:

Kituo cha KulehemuKituo cha Kulehemu
Mita-nyingi ya dijitali ya maabaraMita-nyingi ya dijitali ya maabara
Chanzo cha Umeme cha Meza KinachorekebishwaChanzo cha Umeme cha Meza Kinachorekebishwa
Miwani ya usalama iliyo waziMiwani ya usalama iliyo wazi
3

Build the same logic as blocks

Eneo la Kazi la Blockly

Loading Blockly workspace...

Zana zinazohitajika:

Kompyuta ya mezaniKompyuta ya mezani
4

Simulate, simplify, and count the contacts

Inapakia daftari la Jupyter…

Zana zinazohitajika:

Kompyuta ya mezaniKompyuta ya mezani
5

Measure the switching time, and find the ceiling

Relay logic works perfectly and is slow. Measure exactly how slow, because that number ends the era.

  1. Drive a relay coil with a square wave and put the oscilloscope on both the drive and the contact output.
  2. Measure the delay from coil energising to contacts closing, and again for release.
  3. Watch the contact closure closely at high sweep speed.
  4. Chain three relays so each drives the next, and measure the total delay.

A relay takes something like 5 to 20 milliseconds to switch, and the contacts BOUNCE for a millisecond or two after closing. Chain them and the delays add, so a computation passing through fifty gates takes most of a second.

The bounce is its own problem: a single logical transition arrives as a burst of several, and any counter downstream counts them all. Debouncing exists because a mechanical contact does not close once.

So the ceiling is mechanical, not logical. The algebra is fine and the relay is honest; it simply has mass, and mass takes time to move. The escape is a switch with no moving parts at all — the vacuum tube, which switches in microseconds, and then the transistor, which does it without the heat. That is the rest of this batch.

Vifaa kwa hatua hii:

ReleiRelei3 vipande
Seti ya vizuizi vya umemeSeti ya vizuizi vya umeme1 kifaa

Zana zinazohitajika:

OsilosikopuOsilosikopu
Kizalisha MawimbiKizalisha Mawimbi
Mita-nyingi ya dijitali ya maabaraMita-nyingi ya dijitali ya maabara
Chanzo cha Umeme cha Meza KinachorekebishwaChanzo cha Umeme cha Meza Kinachorekebishwa

Vifaa

5

Zana Zinazohitajika

7

Blueprint zinazohusiana

Blueprint hizi zinashiriki maarifa — mbinu, vifaa au kanuni

The Telegraph Relay

The Telegraph Relay

na EdFI

Elektroniki

40
0
0
0
2
0
Boolean Algebra

Boolean Algebra

na EdFI

TEKNOLOJIA

31
0
0
0
0
0
Binary Arithmetic

Binary Arithmetic

na EdFI

TEKNOLOJIA

31
0
0
0
0
0

CC0 Umma Wote

Mchoro huu umetolewa chini ya CC0. Uko huru kunakili, kubadilisha, kusambaza, na kutumia kazi hii kwa madhumuni yoyote, bila kuomba ruhusa.

Saidia Mtengenezaji kwa kununua bidhaa kupitia Mchoro wao ambapo wanapata Kamisheni ya Mtengenezaji iliyowekwa na Wachuuzi, au unda marudio mapya ya Mchoro huu na uiunganishe kama kiungo katika Mchoro wako kuchangia mapato.

Majadiliano

(0)

Ingia kujiunga na majadiliano

Inapakia maoni...