1. JC Technology
Relay

2. Relay Parts of a Relay Un-magnetised = de-energised Armature Pivot
Soft Iron
core
Coil of wire
Coil Contacts
Switch Contacts
Un-magnetised = de-energised

3. Relay Current through coil magnetises soft iron core
Armature pivots- attracted to core
Contacts close - switching on secondary circuit +V 0V
SPST Relay
Magnetised = Energised

4. Relay SPDT Relay Three switch contacts – act as SPDT switch
De-energised
Energised

5. Relay DPDT Relay Six switch contacts – act as DPDT switch De-energised

6. Relay Interface device – connects two circuits together
Primary circuit – connected to coil
Secondary circuit – connected to contacts
Separate electrical circuits

7. Relay Connects circuits needing different voltages to work
Low voltage controlling high voltage Or
High voltage controlling low voltage

8. Relay Sensor circuits used as primary circuit
Fan motor turned on when its hot
Automatic control

9. Relay
DPDT Relay
Automatic control of motor – curtains opening

10. Relay Relay Alarm Circuit Burglar opens door alarm sounds
Problem: burglar closes door alarm goes off !!!!

11. Relay Latched Relay Alarm Circuit Alarm stays on when door is closed

12. Relay
Reset the alarm
PTB de-energises the relay