Kval 990-HQ, Service Manual

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About a Typical Pneumatic Circuit
4-12
990-HQ Service Manual
About a Typical Pneumatic Circuit
A control valve (solenoid) is used to drive cylinders to move different loads in the machine. The
solenoid if controlled by the PLC by applying a high voltage or a low voltage to a control coil.
Controls for example are: extending and retracting router, drill, clamping a door.
PLC
Output
High
Pressure
Air
Cylinder
Common
Control Circuit
ON
Measure
24 VDC here
Control Voltage
Should have High
Pressure air here
Cylinder
Control
Control
(Coil)
Input
Air
Input
Air
Output
Valve
Should have High
Pressure air on
Activated Output
Schematic Drawing of Pneumatic Circuit
Note: Pre-2006
machines may
not contain the
24 Volt relay.
120 Vac is
directly fed into
the Control Coil.
Check the input
circuitry to the
Control Coil for
120 Vac.
Note: In this
sample set-up,
Port A is nor-
mally open and
Port B is nor-
mally closed. If
power is OFF,
air should be on
Port B.
FIGURE4- 7.
Block Diagram of a Pneumatic Circuit