2. Electro-Pneumatic Circuit
2Dr. S. N. Teli
Que1: Explain about Relay.
Solution: A relay is an electrically operated switch. It consists of a set of input
terminals for a single or multiple control signals, and a set of operating contact
terminals. The switch may have any number of contacts in multiple contact forms,
such as make contacts, break contacts, or combinations thereof.
This is a drawing of a de-energized relay,
When no current is flowing in the
electromagnet coil the armature is pulled up by
the spring and its COM contact connects to the
NC contact.
This is a drawing of an energized relay. When a
voltage is applied to the electromagnet coil the
current flowing in the coil produces magnetic
energy in the iron core which pulls the armature
down. When the armature pulls down the COM
contact switches from NC to NO.
3. Electro-Pneumatic Circuit
Fig: Direct Method
Solution:
3Dr. S. N.Teli
Que 2: Draw electric circuit for AND logic using direct and indirect
method.
+24V
0V
S1
3
4
S2
3
4
OutputB
1 +24V
0V
S1
3
4
S2
3
4
BR
A1
A2
R
3
4
1 2
2
Fig: In Direct Method
R-Relay
4. Electro-Pneumatic Circuit
Fig: Direct Method
Solution:
4Dr. S. N.Teli
Que 3: Draw electric circuit for OR logic using direct and indirect
method.
Fig: In Direct Method
+24V
0V
S1
3
4
S2
3
4
B
1 2 3 +24V
0V
S1
3
4
S2
3
4
R
A1
A2
Relay
R
3
4
B Output
1 2 3 4
4
5. Electro-Pneumatic Circuit
5Dr. S. N.Teli
Fig: Latching
Que 4: Explain Latching logic Concept.
Solution: A simple example of
such a situation is a bulb, which
is started by pressing a button
switch. Although the switch
contacts do not remain closed, it
is required that the bulb
continue to run until a stop
button switch is pressed.
The latching used to stay the
bulb run until the push button is
pressed again.
START- Normally Open (NO)
Push button; OFF- Normally
Closed (NC) Push button.
START
3
4
OFF
1
2
R
A1
A2
+24V
0V
R
3
4
R
3
4
Bu lbRelay
1
7 8 9
8
9
6. Electro-Pneumatic Circuit
6Dr. S. N. Teli
Que 5: Explain on-delay and off-delay timer.
Solution:
On-delay Timer:
Ex: When the S1 switch is on the
lubricant pump (LP) will start
immediately, but grinding machine (GM)
will start after preset time(say 8 Sec) of
timer. Here T is On-delay Timer.
Off –Delay Timer:
Ex: In a car when key (Switch) is on
both Engine(E) and fan are on at time.
When key is off , the engine will off
immediately but fan(F) will off after
preset time of timer (Say 15 Sec) .
7. Electro-Pneumatic Circuit
7Dr. S. N.Teli
Que 6: if Switch S1 is on then Bulb A is on but Bulb B is on after 5 sec.
If Switch S1 is off, both Bulb should off. Draw a Electric logic ladder.
S1
3
4
+24V
0V
R
3
4
R 5
A1
A2
Bulb A
Bulb B
On-delay timer
Switch
1 3
3
Fig: On-delay Timer
Solution:
8. Electro-Pneumatic Circuit
8Dr. S. N.Teli
Fig: Off-delay Timer
Solution:
Que 7: If Switch S1 is on both bulbs on same time and if switch s1 is
off both bulb should off after 4 Second. Draw a Electric logic ladder.
S1
3
4
+24V
0V
Bulb B
off-delay timer
Switch
R5
A1
A2
R
3
4
Bulb A
1 2
2
9. Electro-Pneumatic Circuit
9Dr. S. N.Teli
Fig: Pneumatic Circuit
Solution:
Que 8: Draw Electro-pneumatic Circuit for A+A-
4 2
5
1
3
A+ A-
S1 S2
S1
3
4
A+ A-
+24V
0V
S2
3
4
1 2
S1 and S2 are sensors; A+ and A- are Solenoids
Fig: Electric Ladder Logic Circuit
10. Electro-Pneumatic Circuit
10Dr. S. N.Teli
Fig: Pneumatic Circuit
Solution:
Que 9: Draw Electro-pneumatic Circuit for A+A- using Relay.
4 2
5
1
3
A+ A-
S1 S2
S1 and S2 are sensors; A+ and A- are Solenoids; K1 and K2 are Relays
Fig: Electric Ladder Logic Circuit
S1
3
4
A-
+24V
0V
K2
3
4
K1
3
4
K1
A1
A2
A+
S2
3
4
K2
A1
A2
1 2 3 4 5
2 5
11. Electro-Pneumatic Circuit
11Dr. S. N.Teli
Fig: Pneumatic Circuit
Solution:
4 2
5
1
3
A+ A-
S1 S2
S1 and S2 are sensors; A+ and A- are Solenoids; K1 and K2 are Relays
Fig: Electric Ladder Logic Circuit
Que 10: Draw Electro-Pneumatic Circuit for A+ A- using latching Circuit.
S1
3
4
+24V
K1
A1
A2
0V
K1
3
4
Relay
S2
1
2
S1
3
4
A+
S2
3
4
S1
1
2
K2
A1
A2
K2
3
4
A-
K2
3
4
1 2 3 4 5
6
2 5
6
12. Electro-Pneumatic Circuit
12Dr. S. N. Teli
Fig: Pneumatic Circuit
Solution: S1& S2 are sensors; A+& A- are Solenoids;T1&T2 are on-delay timers
Fig: Electric Ladder Logic Circuit
Que11: Draw an Electro-Pneumatic Ckt for (Delay)A+(Delay)A-.
+24V
0V
S1
3
4
T1 5
A1
A2
On-delay Timer
T1
3
4
A+
S2
3
4
T2 10
A1
A2
T2
3
4
A-
On-delay Timer
1 2 3 4
2 4
4 2
5
1
3
A+ A-
S1 S2
13. Electro-Pneumatic Circuit
13Dr. S. N. Teli
Fig: Pneumatic Circuit
Solution: S1& S2 are sensors; A+& A- are Solenoids;T is on-delay timer.
Fig: Electric Ladder Logic Circuit
Que12: Draw Electro-Pneumatic circuit for A+ (delay) for multi-cycle.
4 2
5
1
3
A+
S1 S2 +24V
0V
S1
3
4
R
A1
A2
S2
3
4
T 5
A1
A2
R
3
4
T
1
2
R
3
4
A+
1 2 3 4 5 6 7
4
7
2
