Releiau

Relay

Switsh dan reolaeth maes magnetig yw relái; mae’n galluogi rheoli cerhyntau/folteddau mawr iawn o system electronig â phŵer isel. Mae dau ddarn i’r relái:

  1. Y coil, sef gwifren o gopr enamlog wedi’i lapio o amgylch craidd haearn meddal; dyma sy’n cynhyrchu’r maes magnetig trwy ddefnyddio cerrynt bach o’r system electronig.
  2. Yr armatwr a’r cyswllt; mae’r maes magnetig a gynhyrchir gan y coil yn tynnu’r armatwr siâp L i gau’r cyswllt (mae’r rhan fwyaf o releiau’n gallu newid drosodd, fel bod modd cysylltu mewnbwn cyffredin â dau allbwn gwahanol).

Heb ddim cerrynt yn llifo trwy’r coil, mae’r armatwr yn y safle a ddangosir. Mae cyswllt switsh C1 yn cyffwrdd cyswllt C2. Pan gaiff cerrynt bach ei basio trwy’r coil, ffurfir electromagnet. Caiff yr armatwr ei atynnu tuag at y pegwn ar waelod yr electromagnet. Bydd yr armatwr yn troi ar ei golyn ac yn gwthio C2 i ffwrdd oddi wrth C1 i greu cyswllt â C3 Pan gaiff y cerrynt ei ddiffodd, bydd yr electromagnet yn colli’i fagnetedd ac aiff yr armatwr yn ôl i’r safle a ddangosir.

CYMWYSIADAU

Defnyddir switshis relái pan fydd angen:

  • rheoli cerrynt mawr trwy gyfrwng cerrynt bach.
  • ynysu cylchedau foltedd isel oddi wrth adran foltedd uwch.

ENGHREIFFTIAU

CYLCHED MODUR CYCHWYN CAR

Mae modur cychwyn car yn tynnu cerrynt trwm iawn pan fydd yn troi’r injan. Mae angen dargludyddion trwchus iawn i gario cerrynt y modur.

System cychwyn car.

Defnyddir y switsh cychwyn i reoli relái. Fydd coil y relái ddim ond yn tynnu cerrynt bach i weithio. Gellir defnyddio dargludyddion main i gysylltu’r switsh cychwyn â choil y relái. Gellir arbed cryn dipyn ar gost dargludyddion trwy osod y switsh relái’n agos at y batri a’r modur cychwyn.

GOLAU CYNTEDD AWTOMATIG

Mae’r system hon yn cynnau golau cyntedd pan fydd hi’n tywyllu. Mae’n debyg y byddai’r cylched electronig a ddefnyddir i ganfod newidiadau yn nwysedd y golau’n gweithio ar gyflenwad batri 9V. Byddai’n rhaid gweithio’r bylb golau ar brif gyflenwad 230 volt.

SYNHWYRYDD LEFEL GOLAU (foltedd isel) - RELÁI (Switsh) - LAMP(Foltedd Prif gyflenwad)

A relay is a switch controlled by a magnetic field; the relay enables the control of very large currents / voltages from a low power electronic system. The relay is constructed in 2 sections:

  1. The coil, which is enamelled copper wire rapped around a soft iron core; this produces the magnetic field using a small current form the electronic system.
  2. The armature and contact, the magnetic field produced by the coil pulls the L shaped armature to close the contact (most relays have a change over operation, were a common input can be connected to 2 different outputs).

With no current flowing through the coil, the armature is in the position shown. Switch contact C1 touches contact C2. When a small current is passed through the coil, an electromagnet is formed. The armature is attracted towards the pole at the bottom of the electromagnet. The armature turns on its pivot and pushes C2 away from C1 to make contact with C3. When the current is switched off, the electromagnet loses its magnetism and the armature returns to the position shown.

APPLICATIONS

Relay operated switches are used when:

  • we wish to control a large current by means of a small current.
  • we need to isolate low voltage circuits from a higher voltage section.

EXAMPLES

CAR STARTER MOTOR CIRCUIT

A car starter motor draws a very heavy current when it turns over the engine. Very thick conductors are required to carry the motor current.

Car starter system.

The relay coil only draws a small current to operate. Thin conductors can be used to link the starter switch to the relay coil. Considerable savings on the cost of conductors can be made by placing the relay switch near the battery and starter motor.

AUTOMATIC PORCH LIGHT

This system switches on a porch light when it gets dark. The electronic circuit used to detect changes in light intensity would probably be operated on a 9V battery supply. The light bulb would have to be operated on a 230 volt mains supply.

LIGHT LEVEL DETECTOR (low voltage) - RELAY OPERATED SWITCH - LAMP (Mains voltage)