1. Relay Logic

2. Relay Logic

3. Basic Relays
A relay is an electronic control switch used to open or close a mechanical contact whenever a voltage is applied to its coil.

4. Basic Relays
A basic relay usually contains two sets of contacts, normally open and normally closed. The schematic will show the normal contact position for a de-energized coil.
Normally Open Contact
Normally Closed Contact

5. Relay Labeling
Always look at the relay case to identify the coil, coil voltage, max current, NO and NC contacts.
Labeling is always shown in a de-energized state.
Contacts
Common NC NO
Coil

6. Simple Relay Logic Ckt.
Which LEDs will illuminate in this circuit with switch 1 open?
With switch 1 closed?

7. Sump Pump Relay Circuit
120 VAC
PUMP
To Sump Probes
What happens when the sump is wet?
What happens when the sump is dry?

8. NAND – Burglar Alarm

9. Relay Logic? (AND, OR, NAND, NOR)

10. Relay Logic? (AND, OR, NAND, NOR)

11. Complete the ckt (AND gate)

12. Complete the ckt (OR gate)

13. Complete the Truth Table

14. Complete the truth table

15. Complete the truth table

16. Motor Starter Circuit

17. Submarine Muzzle Hatch Ckt
K-1-A
Open Hatch Switch
K-2-C
K-3-A
K-4-B
K-6
K-5-A
K-6-G
K-1 = Submarine Surfaced K-2 = Sea Pressure Equalized K-3 = Speed < 5 knots K-4 = Muzzle Hatch open K-5 = Missile Emergency K-6 = Start opening Muzzle Hatch