This document discusses various pneumatic logic circuits that can be created using spool valves. It describes logic AND, OR, NOT, memory/latch circuits and how they function. Diagrams are provided to illustrate 3/2 valves that can be used for normally open, normally closed, selection, and diversion applications. Circuits for OR, AND, NOT logic functions and single pulse creation are also depicted.

1. INDUSTRIAL PNEUMATIC CIRCUIT

3. Logic AND
 Toobtain theoutput Z both
plungers X AND Y must be
operated and held
 If X only isoperated theair
will be blocked at port 1 in
valveY
 If Yonly is operated therewill
be no pressureavailableat
port 1
 If eitherX orY is released the
outputsignal Z will be lost
2
3 1
12 10
2
3 1
12 10
X
Y
Z

4. Logic AND
 Toobtain theoutput Z both
plungers X AND Y must be
operated and held
 If X only isoperated theair
will be blocked at port 1 in
valveY
 If Yonly is operated therewill
be no pressureavailableat
port 1
 If eitherX orY is released the
outputsignal Z will be lost
2
3 1
12 10
2
3 1
X
Y
Z
12 10

5. Logic AND
 Toobtain theoutput Z both
plungers X AND Y must be
operated and held
 If X only isoperated theair
will be blocked at port 1 in
valveY
 If Yonly is operated therewill
be no pressureavailableat
port 1
 If eitherX orY is released the
outputsignal Z will be lost
2
3 1
12 10
2
3 1
12 10
X
Y
Z

6. Logic AND
 Toobtain theoutput Z both
plungers X AND Y must be
operated and held
 If X only isoperated theair
will be blocked at port 1 in
valveY
 If Yonly is operated therewill
be no pressureavailableat
port 1
 If eitherX orY is released the
outputsignal Z will be lost
2
3 1
2
3 1
12 10
X
Y
Z
12 10

7. Logic AND
 Toobtain theoutput Z both
plungers X AND Y must be
operated and held
 If X only isoperated theair
will be blocked at port 1 in
valveY
 If Yonly is operated therewill
be no pressureavailableat
port 1
 If eitherX orY is released the
outputsignal Z will be lost
2
3 1
2
3 1
X
Y
Z
12 10
12 10

8. Logic AND
 Toobtain theoutput Z both
plungers X AND Y must be
operated and held
 If X only isoperated theair
will be blocked at port 1 in
valveY
 If Yonly is operated therewill
be no pressureavailableat
port 1
 If eitherX orY is released the
outputsignal Z will be lost
2
3 1
2
3 1
12 10
X
Y
Z
12 10

9. Logic AND
 Toobtain theoutput Z both
plungers X AND Y must be
operated and held
 If X only isoperated theair
will be blocked at port 1 in
valveY
 If Yonly is operated therewill
be no pressureavailableat
port 1
 If eitherX orY is released the
outputsignal Z will be lost
2
3 1
12 10
2
3 1
12 10
X
Y
Z

10. Logic AND
 This method must not be used
as a two handed safetycontrol
 It is tooeasy toabuse. e.g. one
of the buttonscould be
permanently fixed down and
the system operated from the
other buttononly
 Use the purposedesigned two
handed safetycontrol unit
2
3 1
12 10
2
3 1
12 10
X
Y
Z

11. Logic OR
 Useof an ‘OR’ function shuttle
valve
 SourceX and Ycan be remote
from each otherand remote
from thedestinationof Z
 When X orY is operated the
shuttlevalve seal movesacross
to prevent the signal Z from
being lost through theexhaust
of theothervalve
Y
Z
2
3 1
12 10
2
X
3 1
12 10

12. Logic OR
 Useof an ‘OR’ function shuttle
valve
 SourceX and Ycan be remote
from each otherand remote
from thedestinationof Z
 When X orY is operated the
shuttlevalve seal movesacross
to prevent the signal Z from
being lost through theexhaust
of theothervalve
Y
Z
2
3 1
12 10
2
X
3 1
12 10

13. Logic OR
 Useof an ‘OR’ function shuttle
valve
 SourceX and Ycan be remote
from each otherand remote
from thedestinationof Z
 When X orY is operated the
shuttlevalve seal movesacross
to prevent the signal Z from
being lost through theexhaust
of theothervalve
Y
Z
2
3 1
12 10
2
X
3 1
12 10

14. Logic OR
 Useof an ‘OR’ function shuttle
valve
 SourceX and Ycan be remote
from each otherand remote
from thedestinationof Z
 When X orY is operated the
shuttlevalve seal movesacross
to prevent the signal Z from
being lost through theexhaust
of theothervalve
Y
Z
2
3 1
12 10
2
X
3 1
12 10

15. Logic OR
 Useof an ‘OR’ function shuttle
valve
 SourceX and Ycan be remote
from each otherand remote
from thedestinationof Z
 When X orY is operated the
shuttlevalve seal movesacross
to prevent the signal Z from
being lost through theexhaust
of theothervalve
Y
Z
2
3 1
12 10
2
X
3 1
12 10

16. Logic NOT
 A logic NOT applies to the
stateof theoutputwhen the
operating signal is present
(the output is simply an
inversionof theoperating
signal)
 Thevalve shown is a normally
open type (inlet port
numbered 1)
 When thesignal X is present
there is NOT outputZ
 When X is removed output Z
is given
2
1 3
12 10
Z
X

17. Logic NOT
 A logic NOT applies to the
stateof theoutputwhen the
operating signal is present
(the output is simply an
inversionof theoperating
signal)
 Thevalve shown is a normally
open type (inlet port
numbered 1)
 When thesignal X is present
there is NOT outputZ
 When X is removed output Z
is given
2
1 3
12 10
Z
X

18. Logic NOT
 A logic NOT applies to the
stateof theoutputwhen the
operating signal is present
(the output is simply an
inversionof theoperating
signal)
 Thevalve shown is a normally
open type (inlet port
numbered 1)
 When thesignal X is present
there is NOT outputZ
 When X is removed output Z
is given
2
1 3
12 10
Z
X

19. Logic MEMORY
 A logic MEMORYallows the
output signal state (ON or
OFF) to be maintained after
the input signal has been
removed
 Any bi-stablevalve is a logic
MEMORY
 With this leverdetented valve,
once the lever has been moved
X directionorYdirection it
can be released and will stay
in thatposition
Z
X
3 1
10
Y
12

20. Logic MEMORY
 A logic MEMORY allows the
output signal state (ON or
OFF) to be maintained after
thesignal thatset it has been
removed Z
X
3 1
12 10
Y

21. Logic MEMORY
 A bi-stabledoublepilotvalve
can be setorresetsimply bya
pulse (push and release) on
buttonsX orY
Z
3 1
2
Y
3 1
12 10
2
X
3 1
12 10
12 10

22. Logic MEMORY
 A bi-stabledoublepilotvalve
can be setorresetsimply bya
pulse (push and release) on
buttonsX orY
Z
3 1
2
Y
3 1
12 10
2
X
3 1
12 10
12 10

23. Logic MEMORY
 A bi-stabledoublepilotvalve
can be setorresetsimply bya
pulse (push and release) on
buttonsX orY
Z
3 1
2
Y
3 1
12 10
2
X
3 1
12 10
12 10

24. Logic MEMORY
 A bi-stabledoublepilotvalve
can be setorresetsimply bya
pulse (push and release) on
buttonsX orY
Z
3 1
2
Y
3 1
12 10
2
X
3 1
12 10
12 10

25. Logic MEMORY
 A bi-stabledoublepilotvalve
can be setorresetsimply bya
pulse (push and release) on
buttonsX orY
Z
3 1
2
Y
3 1
12 10
2
X
3 1
12 10
12 10

26. Logic MEMORY (latch)
 A popular memorycircuit is
the latch
 Will not re-make after
pneumaticpower failure
 A pulse on X operates the
pilot / spring valve to give
output Z
 A feedback from Z runs
through the normallyopen
valveY to latch theoperation
of Z when X is released
 A pulseon Y breaks the latch
and Z is exhausted
X
Y
Z
3 1
2
3 1
12 10
10
12
2
1 3
12 10

27. Logic MEMORY (latch)
 A popular memorycircuit is
the latch
 Will not re-make after
pneumaticpower failure
 A pulse on X operates the
pilot / spring valve to give
output Z
 A feedback from Z runs
through the normallyopen
valveY to latch theoperation
of Z when X is released
 A pulseon Y breaks the latch
and Z is exhausted
X
Y
Z
3 1
2
3 1
12 10
12 10
2
1 3
12 10

28. Logic MEMORY (latch)
 A popular memorycircuit is
the latch
 Will not re-make after
pneumaticpower failure
 A pulse on X operates the
pilot / spring valve to give
output Z
 A feedback from Z runs
through the normallyopen
valveY to latch theoperation
of Z when X is released
 A pulseon Y breaks the latch
and Z is exhausted
X
Y
Z
3 1
2
3 1
12 10
12 10
2
1 3
12 10

29. Logic MEMORY (latch)
 A popular memorycircuit is
the latch
 Will not re-make after
pneumaticpower failure
 A pulse on X operates the
pilot / spring valve to give
output Z
 A feedback from Z runs
through the normallyopen
valveY to latch theoperation
of Z when X is released
 A pulseon Y breaks the latch
and Z is exhausted
X
Y
Z
3 1
2
3 1
12 10
2
1 3
12 10
12 10

30. Logic MEMORY (latch)
 A popular memorycircuit is
the latch
 Will not re-make after
pneumaticpower failure
 A pulse on X operates the
pilot / spring valve to give
output Z
 A feedback from Z runs
through the normallyopen
valveY to latch theoperation
of Z when X is released
 A pulseon Y breaks the latch
and Z is exhausted
X
Y
Z
3 1
2
3 1
12 10
2
1 3
12 10
12 10

32. Logic circuits (spool valves)
 5/2 OR
 Single pulse control
 Air conservation
 Double flow
 Counting
 NO / NC
 Selection / Diversion
 Latch
 OR, AND, NOT
 Single pulse maker
 Slow pressure build
 Pre-select

33. 3/2 NO / NC
 A fully balanced valveallows
pressureon any potor
combinationof ports
 A singlevalvecan be used
normallyopen or normally
closed
 For normallyopen thesupply
pressure is connected toport 1
 For normallyclosed the supply
pressure is connected toport 3
2
3 1
12 10
2
3 1
12 10

34. 3/2 NO / NC
 A fully balanced valveallows
pressureon any potor
combinationof ports
 A singlevalvecan be used
normallyopen or normally
closed
 For normallyopen thesupply
pressure is connected toport 1
 For normallyclosed the supply
pressure is connected toport 3
2
3 1
12 10
2
3 1
12 10

35. 3/2 Valve selection / diversion
 Selection of one of two
supplies connected toports 1
and 3 can be different
pressures
 Diversionof one supply toone
of twooutlets
 If it is required toexhaust the
downstreamaira 5/2 valve is
required
2
3 1
12 10
2
3 1
12 10

36. 3/2 Valve selection / diversion
 Selection of one of two
supplies connected toports 1
and 3 can be different
pressures
 Diversionof one supply toone
of twooutlets
 If it is required toexhaust the
downstreamaira 5/2 valve is
required
2
3 1
2
3 1
12 10
12 10

37. Latch with controls
 In thisversionof a latch the
push buttonvalves are
connected toperform ‘OR’
and ‘NOT’ functions
 The ‘OFF’ valve must be
placed last in the signal chain
so that if bothvalvesare
operated togetherthe ‘OFF’
command will dominateover
the ‘ON’ command
2
3 1
12 10
2
3 1
10
2
3 1
10
ON 12
OFF 12
Out

38. OR, AND, NOT
 A single 3/2 pilot operated
spring returnvalvecan be use
foranyof these logic functions
 x OR y gives output z
 x AND y gives output z
 x gives NOT z
3 1
12 10
12 10
12 10
AND
OR
NOT
x y
z 2
x
3 1
y
z 2
3 1
x
z 2

39. Single pulse maker
 Convertsa prolonged signal x
intoa single pulse z
 Signal z must be removed to
allow thevalve to reset then x
can beapplied again
 Thedurationof the pulsecan
be adjusted with the flow
regulator
2
3 1
12 10
x
z

40. Slow initial pressure build up
 Choosea 3/2 pilotspring valve
with a relatively high
operating forcee.g. 3 to 4 bar
 When the quick connect
coupling is made, theoutput
at port 2 is controlled at the
rateof the f low regulator
setting
 When the pressure is high
enough tooperate thevalve
full flow will takeover
2
3 1
12 10

41. Pre-select
 The lever valve can pre-select
the movement of the cylinder
OUT or IN
 The movement will occur the
next time the plunger valve is
operated
 The plungervalvecan be
released immediatelyand
subsequently operated and
released any numberof times
2
3 1
12 10
2
3 1
12 10
2
3 1
12
10
OUT/IN
pre-select

42. 5/2 OR function
 Thevalveat position ‘a’ is
reversed connected and
supplied from thevalve
conventionallyconnected at
position ‘b’
 Thecylindercan becontrolled
from either position ‘a’ ‘OR’
position ‘b’
1
2
4
5 3
14
12
2
4
5 1 3
14
12
a
b

43. Single pulse control
 Each time the foot
operated valve is pressed
thecylinderwill single
stroke + and - alternately
 First footoperation the
cylinder movesout
 Second footoperation
thecylinder moves in
 Third….. outand soon
2
4
14
12
2
3 1
12 10
5 1
12 10
2
3 1
3 1
12 2
10

44. Air conservation
 Powerstroke in the instroke
directiononly
 Differential area of the piston
gives an outstroke force when
the pressure is balanced
 Airused tooutstroke is
equivalent toacylinderwith
only thesame boreas the rod
diameter
 Assumes the cylinder is not
loaded on the plus strokeand
low friction
2
4
1
5
14
12

45. Air conservation
 Powerstroke in the instroke
directiononly
 Differential area of the piston
gives an outstroke force when
the pressure is balanced
 Airused tooutstroke is
equivalent toacylinderwith
only thesame boreas the rod
diameter
 Assumes the cylinder is not
loaded on the plus strokeand
low friction
2
4
1
5
14
12

46. Double flow
 Wherea larger 3/2 valve is not
available
 Two f low paths in a 5/2 valve
each with a separate supply
can bearranged togivedouble
f loworsupply separate
devices
 Ensure the tube size to the
cylinder is large enough to
take thedouble flow
4 2
12
14
5 1 3

47. Double flow
 Wherea larger 3/2 valve is not
available
 Two f low paths in a 5/2 valve
each with a separate supply
can bearranged togivedouble
f loworsupply separate
devices
 Ensure the tube size to the
cylinder is large enough to
take thedouble flow
4 2
12
14
5 1 3

48. Counting
 Counting applications are
bestachieved with electro-
mechanical orprogrammable
electroniccounters
 Pneumaticcounting circuits
use large numbers of logic
valvesand can be slow
 Thecounting chain shown
will count to 4
 Red and blue are non-
overlapping alternatepulses,
purple is the reset line
2
1
3
4

49. Counting application
 The counting circuit is
applied tocount 4 strokesof a
cylinder
 At restall counting valves are
held reset by thestartvalve
 Startoutstrokes ‘A’
 Alternatesignals from ‘a1’ and
‘a0’ progressesoperation of
the counting valves up the
chain
 On the 4th operation of ‘a1’
the green signal resets the
startvalve tostop thecylinder
A
a0
a1
a0 a1
Start

51. Time delay
 A signal is restricted toslow
the rateof pressure build up
on a pressure switch (3/2
differential pressureoperated
valve)
 When the pressure switch
operates astrong un-restricted
output is given
 A reservoirprovides
capacitance toallow less fine
and sensitivesettingson the
f low regulatormaking iteasy
toadjust
1
2
3
12 10
Signal
in
Output

52. Time delay
 Manual remotestartof a
doubleacting cylinderwith a
timedelay in theoutstroked
position beforeautomatic
return
2
2
4
5 1 3
14 12
3 1
12 10
- +
A
a1
2
3 1
12 10
a1
1
3
12
2
10

53. Pressure decay
Manual remote start of a double acting
cylinder
Uses a low pressure operated valve connected
normally open
When the back pressure in the front of the
cylinder falls below 0.1 bar the return signal is
given
Connection taken between the cylinder and
f low regulator
Useful for pressing work pieces of variable
size
2
4
5 1 3
14 12
2
3 1
12 10
- +
A
a1
2
12
10
1 3 0.1bar

54. Electro-pneumatic
The majority of systems use electrical/electronic
control due to the high degree of sophistication
and flexibility
Solenoid valves are used to control cylinders
Feedback signals are from reed switches,
sensors and electrical limit switches
Logic is hard wired or programmed in to a
PLC (programmable logic controller)
a0 a1
2
4
14 12
5 1 3
A
 Circuit building block for
each cylinder
a0 a1