3442 Industrial Instruments 2 Chapter 7 Final Control Princess Sumaya University 3442 - Industrial Instruments 2 Princess Sumaya Univ. Electronic Engineering Dept. 3442 Industrial Instruments 2 Chapter 7 Final Control Dr. Bassam Kahhaleh Dr. Bassam Kahhaleh

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Objective The function of the final control element is to translate low-energy control signals into a level of action commensurate with the process under control.

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Operation Block Diagram Signal Conversions Actuator Control Signal Final Control Element Process

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Operation Block Diagram Signal Conversions Actuator Control Signal The devices that perform such signal conversions are often called transducers because they convert control signals from one form to another, such as current to pressure, current to voltage … etc. Final Control Element Process

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Operation Block Diagram Signal Conversions Actuator Control Signal Final Control Element The actuator is a translation of the (converted) control signal into action on the control element. Process

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Operation Block Diagram Signal Conversions Actuator Control Signal Final Control Element The control element is operated (run) by the actuator. Process

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Operation Block Diagram Signal Conversions Actuator Control Signal Final Control Element The process is operation (objective) under control. Process

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Operation Example: Baking of Crackers

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Signal Conversions Analog Electrical Signals Relays Mechanical Solid-State Amplifiers Transistor Op-amp

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Signal Conversions Analog Electrical Signals Relays Mechanical

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Signal Conversions Analog Electrical Signals Relays Mechanical

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Signal Conversions Analog Electrical Signals Relays Mechanical

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Signal Conversions Analog Electrical Signals Op-amp Example: Convert a “4 – 20” mA control signal to a “5 – 10” V signal. 4 20 I (mA) V (Volts) 5 10 Solution: Vin = Rin * Iin Vout = K Vin + VB

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Signal Conversions Analog Electrical Signals Op-amp Solution: Vin = Rin * Iin Let Rin = 100 Ω 0.4 2 Vin (V) Vout (V) 5 10

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Signal Conversions Analog Electrical Signals Op-amp Solution: Vout = K Vin + VB 5 = K * 0.4 + VB 10 = K * 2 + VB K = 3.125 VB = 3.75 Vout = 3.125 Vin + 3.75 Vout = 3.125 (Vin + 1.2) 0.4 2 Vin (V) Vout (V) 5 10

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Signal Conversions Analog Electrical Signals Op-amp Solution: Vout = 3.125 (Vin + 1.2)

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Signal Conversions Digital Electrical Signals Op-amp DAC Direct Action Example: A 4-bit digital word is intended to control the setting of a 2-Ω DC resistive heater. Heat output varies as a 0 – 24 V input to the heater. Using a 10–V DAC followed by an amplifier and a unity gain high-current amplifier, calculate: a) the settings from minimum to maximum heat dissipation, and b) how the power varies with LSB changes.

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Signal Conversions Digital Electrical Signals DAC Solution: DAC 10–V reference  24 = 16 Therefore: 1111  (15/16) * 10 = 9.375 V . 0000  0 V Amplifier gain = 24 / 9.375 = 2.56 Incremental step = [(1/16) * 10 ] * 2.56 = 1.6 V ΔV = (1/16) * 10 V

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Signal Conversions Digital Electrical Signals DAC Power (W) Solution: ΔP (from 0000 to 0001) = (1.6 V)2 / 2 Ω = 1.28 W ΔP (from 1110 to 1111) = (24)2 – (22.4)2 / 2 = 37.12 W Control Ward

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Signal Conversions Pneumatic Signals Pressure signal travels down the pipe at a speed in the range of the speed of sound.

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Signal Conversions Pneumatic Signals Pressure signal travels down the pipe at a speed in the range of the speed of sound. Amplifier (booster or relay)

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Signal Conversions Pneumatic Signals Pressure signal travels down the pipe at a speed in the range of the speed of sound. Amplifier (booster or relay) Nozzle/Flapper system

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Signal Conversions Pneumatic Signals Pressure signal travels down the pipe at a speed in the range of the speed of sound. Amplifier (booster or relay) Nozzle/Flapper system Current-to-Pressure converters

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Industrial Electronics Silicon-Controlled Rectifier (SCR) Maximum forward current Peak reverse voltage Trigger voltage Trigger current Holding current

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Industrial Electronics SCR Operation: Half-wave

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Industrial Electronics SCR Operation: Full-wave

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Industrial Electronics SCR Operation: Full-wave (with digital control)

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Industrial Electronics SCR Example An SCR with a 4.0–V trigger is used as a light–dimmer control. What resistance, R, should be used to provide approximately 10% to 90% ON time?

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Industrial Electronics SCR Example

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Industrial Electronics SCR Example VC(t) = VO(1 – e-t/RC) 4.0 = 10 (1 – e-t/RC) t = 0.511 RC T half a cycle = 10 ms 10%  1 ms 90%  9 ms With C = 0.12 μF Rmin = 16.3 KΩ Rmax = 147 KΩ

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Industrial Electronics TRIAC DIAC

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Industrial Electronics TRIAC

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Industrial Electronics TRIAC Example An DIAC with a 28–V breakdown voltage is used in the light–dimmer control. What resistance, R, should be used to provide approximately 10% to 90% ON time?

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Industrial Electronics TRIAC Example When does VAC reach 28 Volts so that it becomes possible to trigger the TRIAC? 28 = 310 sin(314 t) t = 0.288 ms ≈ 2.9% of the period And for 40 Volts: 40 = 310 sin(314 t) t = 0.412 ms ≈ 4.1% of the period

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Industrial Electronics TRIAC Example 28 = 40 [ 1 – e – t / RC ] t = 1.2 RC If t = 1 ms: Rmin = 6.9 KΩ If t = 9 ms: Rmax = 62.5 KΩ

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Actuators Electrical Actuators Solenoid

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Actuators Electrical Actuators Solenoid DC Motor AC Motor

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Actuators Electrical Actuators Solenoid DC Motor AC Motor Stepping Motor

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Actuators Electrical Actuators Solenoid DC Motor AC Motor Stepping Motor Pneumatic Actuators

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Actuators Electrical Actuators Solenoid DC Motor AC Motor Stepping Motor Pneumatic Actuators Hydraulic Actuators

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Control Elements Mechanical Solid-Material Hopper Valves

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Control Elements Mechanical Paper Thickness

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Control Elements Electrical Motor Speed Control

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Control Elements Electrical Temperature Control

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control Control Elements Fluid Valves

3442 - Industrial Instruments 2 Princess Sumaya University 3442 - Industrial Instruments 2 7: Final Control End of Chapter 7