PID Temperature Controller

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					PID Temperature Controller

  Allen Bradley 1771-TCM

        Brian Van Eyk
• Applications
   – Plastic injection molding
   – Powder paint
• There is a need for quick and accurate temperature control
• Two solutions
   – Sensor with simple logic controller
   – Smart I/O controller
              Allen Bradley 1771-TCM
• Uses PID controller
• 8 independent control loops
   – Heating or cooling control
• Auto-Tuning software
   – Speeds up design
   – Accurate gains
• Analog or digital control
• Standard PLC-5 rack mount
                                  Control Loops
• Thermocouples used for feedback
   – Open loop detection
   – Disable unit or output constant value
• Data collected in the TCM is given to the PLC
• PLC controls actuator
                            PID Auto-Tuning
– Auto-Tune calculates PID gains
   – Gains are stored in TCM module
   – Gains must be read into PLC data table
   – TCM can be set to slow, medium or fast response time
   – TCM memory is volatile
– TCM must have gains sent to it or auto-tune whenever
  power to the module is lost
                          PID Fine-Tuning

Fine tuning can be done manually
  – Too much overshoot
     • Decrease P and I
     • Increase D
  – Too slow
     • Increase P and I
     • Decrease D
            Analog vs. Digital Control

•    TCM module has two possible outputs:
    1. Analog control allows PLC to set the
       temperature of the heating / cooling device
    2. Digital control gives the PLC the duty cycle
       for the actuator
• Alarms can be set
    – High and low temperature alarm values
    – High and low deviations
    – Can use with dead band or without
• Alarm is sent to the PLC
    – The PLC programmer can do
      what they want with the alarm
• Termination panel mounted separately
   – Standard DIN style
   – Mount in panel near thermocouples
• Two cables from termination panel to TCM
• Provides more accurate temperature readings

• Cost - $3,150

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