3. OBJECTIVES
PROGRAMMING OPTIONS FOR PLCs
LADDER DIAGRAMS
• Statement Lists
• Function Blocks
• Digital Inputs / outputs
• Analog Input / Outputs
PLC Design, Simulation
4/17/2014
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Consultants (GTC) Ltd
4. PROGRAMMING OPTIONS FOR PLCs
PLC Basics
Ladder Logic / Programming
• RSLogix 5000 –
• Micrex sx programming from Fuji Electric
• i-TRILOGI (Ladder + BASIC)
• SYSWIN 3.4 for OMRON
C/C++ to PLC / Ladder Logic
MATLAB
LabVIEW (for NI cRIO, myRIO, myDAQ e. t. c)
4/17/2014
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Consultants (GTC) Ltd
5. PLC Basics
Function of
a PLC
Inputs and
outputs
Architecture
and wiring
of PLCs
Network
Protocols
4/17/2014
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Consultants (GTC) Ltd
6. Function of a PLC
Microprocessor based
controller with various
inputs and outputs
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7. Function of a PLC
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8. Inputs and Outputs
• These are typically switches or sensors
• Designed with opto – isolators
4/17/2014
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9. Inputs and Outputs
• Relays (volt free)
• Triac
• Transistors
4/17/2014
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10. Architecture and Wiring Diagrams
4/17/2014
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11. Architecture and Wiring Diagrams
4/17/2014
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12. Network Protocols
• Note nature in which I/O devices are
connected
• Note also they are either ON/OFF (hence
digital in nature)
• However, PLC I/O signals are analog (vary
between 4 – 20mA)
• What does this imply ?
4/17/2014
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Consultants (GTC) Ltd
16. Review Questions
1.Switches, proximity devices and sensors are
generally used in what way in a plc
application?
a) Relays
b) Software elements
c) Inputs
d) Outputs
4/17/2014
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Consultants (GTC) Ltd
17. Review Questions
Study the diagram Below
4/17/2014
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18. Revision Questions
Pick the correct statement about it.
a) When the power is switched on to the PLC all the N/O
relay contacts are shown close
b) The 24 V supply shown is used to power the plc itself.
c) The plc energises an output by closing the relevant relay
contact.
d) When the plc outputs are energised they are al l latched
on by the relay contacts shown
4/17/2014
Presented by Global Technocrats and
Consultants (GTC) Ltd
Hinweis der Redaktion
The PLC performs the logic functions of relays, timers, counters and sequencers. It has the following advantages: 1) Low cost 2) Reliability 3) Reprogramability
The PLC inputs give it information about the machine or process that it is controlling. These are typically switches and sensors. The switches are connected to an input module that provides the interface between the switches or sensors and the PLC.Usually designed with opto – isolalators to protect the PLC
The PLC outputs are connected directly or indirectly (e.g. through a relay) to actuator controls. Examples include solenoids on directional control valves, motors, motor contactors, alarms and warning lights.Triac: Used mainly for Alternating Current conditions (requires some form of over current protection)Transistors: For fast switching (used for DC components only/ low voltage situations)
The wiring diagram in Fig 1.5 shows the inputs and outputs connected directly (hard wired) to the PLC. The devices shown are on/off or digital in nature but the signal to the PLC is analog. Many commonly used devices conform to a 4-20 mA standard whereby signals of 4mA and 20mA form respectively the minimum and maximum values of an analog signalWhat does analog signal in PLC imply ? It implies that a separate cable needs to be run between the end device and the control system because only a single analog signal can be represented on the circuit.