This document provides information on electro-hydraulic components including open/closed contact switches, relays, coils, solenoids, and logic circuits. It explains the symbols and functions of these components and how they are used in series and parallel circuits. Memory circuits are also discussed, along with examples of a memory on and memory off circuit. Relays are described as helping to switch small currents to larger ones and providing safety and interlocking capabilities. Solenoids function to switch valves on and off based on being energized or not.

2.  By the end of this lecture, student should be
able to:
◦ Explain electro-hydraulic components symbol and
function: series and parallel circuits, open/close
contact switch, OR/AND logic circuit, relay, coil and
solenoid
◦ Design and analyze memory circuit

3. 1. Open Contact Switch
2. Closed Contact Switch
3. Changeover Contact Switch – a combination of an
Open and a Closed Contact Switch. Usually used on
Relay and Limit Switch.

4. YES (Identity) Gate
+24V
0V

5. NOT (Negation) Gate
+24V
0V

6. OR (Conjunction) Gate
+24V
0V

7. AND (Disjunction) Gate
+24V
0V

8. +24V
0V

9.  Coil
 Solenoid

10. IMPORTANT COMPONENTS IN
ELECTRO-HYDRAULIC SYSTEMS
RELAY
SOLENOID

11. Consists of a coil and a set of changeover contact switch
Its function includes:
1. To help switch over small
current to larger current
2. To help switch over small
voltage to larger voltage
3. Consists of multiple large
contact switches for
simultaneous switching of
multiple outputs
4. Safety feature: Interlock
capability

12. Coil
Coil connections
Contacts
Contact connections
Return
spring
Cover
Symbol
A1
A2 11
12
14
21
22
24
Armature

13. Symbol
A1
A2 11
12
14
21
22
24
A1 A2 4 2 1

14. Symbol
A1
A2 11
12
14
21
22
24
A1 A2 4 2 1

15. Symbol
A1
A2 11
12
14
21
22
24
A1 A2 4 2 1

16. Symbol
A1
A2 11
12
14
21
22
24
A1 A2 4 2 1

17.  The circuit on the right is a
direct connection without
using relay. The lamp will
switch on as soon as the
contact switch is closed.
 However, if there is a power
surge from the main, then
the user will experience
some form of electric shock.
+24V
0V

18.  The circuit on the right is an
indirect connection with a
relay (K1). Once the switch is
pressed, relay coil (K1) will be
energized. The coil will then
closes the relay switch thus,
switching the lamp.
 The safety measure here is
that, if there is a power surge
from the 240V, then the user
will be protected from any
form of electric shock.
+24V
0V
K1
K1
24 0V
2 different circuits

19.  A solenoid is like a coil of the relay
 When it is energized, it will switch on the valve, similar
to turning on the hand lever of a normal valve.
 If it is a single solenoid valve, then the valve will switch
off automatically through a spring mounted at the
opposite end of the valve.
 If it is a double solenoid valve, then the valve will
switch off only after the second solenoid is being
energized.

20. Single Solenoid Valve Double Solenoid Valve

21. Hydraulic Circuit Symbol Electrical Circuit Symbol
A B
P T
Y1 Y2
A B
P T
Y1
Y1
Y1 Y2

22. F=0
A B
P T
Y1 Y2
+24V
0V
S1
K1
K1
Y1
S2
K2
K2
Y2

23.  Relevancy:
1. Used to build Continuous Cycle circuit.
2. Used to latch a circuit for continuous supply of
electricity to a particular line.
3. Used when replacing a double solenoid valve to a
single solenoid valve of a circuit, without changing
the originality of the circuit function.

24.  Memory ON (Dominant Set)
+24V
0V
ON
K1
K1
OFF
K1
• When ON is pressed, Relay coil K1
will be energized. Both relay K1
switches will close. This means, while
the lamp turns on, the relay switch will
continuously energize the coil.
Therefore, the lamp is permanently on.
Only when the OFF button is pressed,
the lamp will switch off.
• To confirm that this is a Memory ON
circuit, press both ON and OFF
together. The lamp will still light ON.

25.  Memory OFF (Dominant Reset)
• The function of this circuit is
similar to the previous Memory
ON circuit. However, please
note that the OFF button is
placed below the ON button,
not parallel!
• To confirm that this is a
Memory OFF circuit, press both
ON and OFF together. The lamp
will NOT light ON.
+24V
0V
ON
K1
K1
OFF
K1

26.  Proximity -> closeness
 Detect close objects without contact.
 Various types:
1. Inductive sensor
2. Capacitive sensor
3. Optical sensor

27. Used to sense only metal type of object.

28. Used to sense only high density objects.

29. Used to sense only reflective type of object.