MagnetismMagnetism

Auto 2 after series circuits

Magnets & Magnetic FieldsMagnets & Magnetic Fields

Magnetic flux linesMagnetic flux lines

Flux Always flows from North to South

Opposites Attract / Likes repelOpposites Attract / Likes repel

Arrangement of atoms Arrangement of atoms

In metal that In metal that

has has notnot been been magnetizedmagnetized

Arrangement of atomsArrangement of atoms

In metal that In metal that

hashas been been magnetizedmagnetized

PermeabilityPermeability

Ability of materials to become Ability of materials to become magnetizedmagnetized

ReluctanceReluctance

Resistance to magnetic lines of fluxResistance to magnetic lines of fluxHigh reluctance = AirHigh reluctance = Air

Low reluctance = Soft IronLow reluctance = Soft Iron

ElectromagnetismElectromagnetism

Any time current flows thru a conductor,A magnetic field is created around the conductor

ElectromagnetsElectromagnets

Can increase the strength by;Can increase the strength by;– Adding more windingsAdding more windings– Increasing the currentIncreasing the current

» More voltageMore voltage

» less resistanceless resistance

– Wrap windings around Wrap windings around something with low reluctancesomething with low reluctance

Conventional TheoryConventional Theory

Left hand thumb rule applies:With left thumb pointing the way currentFlows, your fingers show you whichWay the magnetic field is built around.

Says:Current flowsFrom Positive “+” to Negative “-”

Electron TheoryElectron Theory

Right hand thumb rule applies:With right thumb pointing the way currentFlows, your fingers show you whichWay the magnetic field is built around.

Says:Current flowsFrom Negative “-”To Positive “+”

SaturationSaturation

Is the point where the magnetic Is the point where the magnetic strength eventually levels offstrength eventually levels off

More windings, the longer it takes More windings, the longer it takes but the stronger the fieldbut the stronger the field

SaturationSaturation

Turn on point

Saturation point

Turn on point Saturation point

Two coil ramps Taken with a Lab Scope and An amp probe.

Shorted coil

About 4.25 mS

Electromagnet questions?Electromagnet questions?

RelaysRelays

RelaysRelays

Use a small amount of current Use a small amount of current to control (switch) a large to control (switch) a large amount of currentamount of current– Control circuit has a winding to Control circuit has a winding to

create a magnetic field (#1 & #3)create a magnetic field (#1 & #3)» Low amp circuitLow amp circuit

» Also called the primaryAlso called the primary

– Controlled circuit has a switch to Controlled circuit has a switch to control current flow to a higher control current flow to a higher amp load (#2 & #4)amp load (#2 & #4)

» Also called the secondaryAlso called the secondary

» High amp circuitHigh amp circuit

Relay in operationRelay in operation

1 & 3 the control circuit

2 & 4 the controlled circuit

Send currentThru 1 & 3 toCreate field

Voltage present at #4Trying to push current

Out #2 to high current load

High currentSwitched to Load out #2

Normally Open and Normally ClosedNormally Open and Normally Closed

Normally Open (N O) RelayTakes energy to switch closedNo energy, switch is open

Normally Closed (N C) RelayTakes energy to switch openNo energy, switch is closed

Normally Open RelayNormally Open Relay

ISO Mini RelayISO Mini Relay

Most manufactures went to this standard

Terminals #30 to #87a are NC and terminals #30 to #87 NO

NC

NO

ISO Mini RelayISO Mini Relay

Terminal #30 comes from B+

Terminal #87 goes to load

Terminal #87a is rarely used (wiper park circuit)

Terminals #85 & #86 are the controlCircuit (winding) usually 70 ohms

ISO Mini RelayISO Mini Relay

ISO Micro RelayISO Micro Relay

Checking RelaysChecking Relays

Find control and controlledCircuits with ohmmeter

Power up control circuitWhile checking controlled

Typical horn circuitTypical horn circuit

In steering wheel

Relay Questions?Relay Questions?

Parallel circuit reviewParallel circuit review

Parallel Circuit RulesParallel Circuit Rules

More than one pathMore than one path– Has a splice in the circuitHas a splice in the circuit

VoltageVoltage stays the same stays the same Total Total AmperageAmperage is divided between the is divided between the

pathspaths Total Total ResistanceResistance is always lower that the is always lower that the

smallest path or branchsmallest path or branch

OHMS LAW STILL WORKS THE SAME

If volts and ohmsAre equal, thenOne amp will flow.

Parallel circuit questions?Parallel circuit questions?

Lets apply what weHave learned.

Don’t panic!Don’t panic!

Apply what you have learned about relays and Apply what you have learned about relays and parallel circuitsparallel circuits

Draw up a typical horn circuitDraw up a typical horn circuit– Remember the horn switch is in the steering wheelRemember the horn switch is in the steering wheel– We don’t want to send the high current through the We don’t want to send the high current through the

horn switch, so we will use a relayhorn switch, so we will use a relay– The horn is the load that will use high ampsThe horn is the load that will use high amps

Make sure there is a complete path in the Make sure there is a complete path in the controlcontrol circuit and the circuit and the controlledcontrolled circuit circuit

YOU CAN DO IT!YOU CAN DO IT!

Apply what you have learned about relays and Apply what you have learned about relays and parallel circuitsparallel circuits

Draw up a typical horn circuitDraw up a typical horn circuit– Remember the horn switch is in the steering wheelRemember the horn switch is in the steering wheel– We don’t want to send the high current through the We don’t want to send the high current through the

horn switch, so we will use a relayhorn switch, so we will use a relay– The horn is the load that will use high ampsThe horn is the load that will use high amps

Make sure there is a complete path in the Make sure there is a complete path in the controlcontrol circuit and the circuit and the controlledcontrolled circuit circuit