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

34423442Industrial Instruments 2Industrial Instruments 2

Chapter 7Chapter 7Final ControlFinal Control

Dr. Bassam KahhalehDr. Bassam Kahhaleh

Princess Sumaya Univ.Princess Sumaya Univ.Electronic Engineering Dept.Electronic Engineering Dept.

Princess Sumaya UniversityPrincess Sumaya University 3442 - Industrial Instruments 23442 - Industrial Instruments 2 22 / 46 / 46

7: Final Control7: Final Control

ObjectiveObjective

The function of the final control element is to The function of the final control element is to translate low-energy control signals into a translate low-energy control signals into a level of action commensurate with the level of action commensurate with the process under control.process under control.


7: Final Control7: Final ControlOperationOperation Block DiagramBlock Diagram

SignalConversions

Actuator

FinalControlElement

Process

Control

Signal



SignalConversions

Actuator

FinalControlElement

Process

Control

Signal

TheThe devices that perform such devices that perform such signal conversions are often signal conversions are often called called transducerstransducers because they because they convert control signals from one convert control signals from one form to another, such as form to another, such as currentcurrent to to pressurepressure, , currentcurrent to to voltagevoltage … … etc.etc.



SignalConversions

Actuator

FinalControlElement

Process

Control

Signal

TheThe actuatoractuator is a translation of is a translation of the (converted) control signal the (converted) control signal into action on the control into action on the control element.element.



SignalConversions

Actuator

FinalControlElement

Process

Control

Signal

TheThe control elementcontrol element is operated is operated (run) by the actuator.(run) by the actuator.



SignalConversions

Actuator

FinalControlElement

Process

Control

Signal

TheThe processprocess is operation is operation (objective) under control.(objective) under control.


7: Final Control7: Final ControlOperationOperationExample: Baking of CrackersExample: Baking of Crackers


7: Final Control7: Final ControlSignal ConversionsSignal Conversions Analog Electrical SignalsAnalog Electrical Signals

RelaysRelays• MechanicalMechanical• Solid-StateSolid-State

AmplifiersAmplifiers• TransistorTransistor• Op-ampOp-amp



RelaysRelays• MechanicalMechanical

Single Pole Single Touch

Single Pole Double Touch

SPST

SPDT

Double Pole Single Touch DPST

Double Pole Double Touch DPDT




NC

NO

NC

NO+ 12 V


L

N

220 VAC

L

N

220 VAC





Op-ampOp-amp

ExampleExample::Convert a “4 – 20” mA Convert a “4 – 20” mA

control signal to a “5 – 10” control signal to a “5 – 10” V signal.V signal.

SolutionSolution::VVinin = R = Rinin * * IIinin

VVoutout = K V = K Vinin + V + VBB

4 20

I (mA)

V (Volts)

5

10



Op-ampOp-ampSolutionSolution::

VVinin = R = Rinin * * IIinin

Let RLet Rinin = 100 = 100 ΩΩ

I

V

in

in

R

0.4 2

Vin (V)

Vout (V)

5

10




VVoutout = K V = K Vinin + V + VBB

5 = K * 0.4 + V5 = K * 0.4 + VBB

10 = K * 2 + V10 = K * 2 + VBB

K = 3.125K = 3.125

VVBB = 3.75 = 3.75

VVoutout = 3.125 V = 3.125 Vinin + 3.75 + 3.75

VVoutout = 3.125 (V = 3.125 (Vinin + 1.2) + 1.2) 0.4 2

Vin (V)

Vout (V)

5

10




Vout = 3.125 (Vin + 1.2)


7: Final Control7: Final ControlSignal ConversionsSignal Conversions Digital Electrical SignalsDigital Electrical Signals

Op-ampOp-amp DACDAC Direct ActionDirect Action

ExampleExample::A 4-bit digital word is intended to control the setting of a A 4-bit digital word is intended to control the setting of a

2-2-ΩΩ DC resistive heater. Heat output varies as a 0 – DC resistive heater. Heat output varies as a 0 – 24 V input to the heater. Using a 10–V DAC followed 24 V input to the heater. Using a 10–V DAC followed by an amplifier and a unity gain high-current amplifier, by an amplifier and a unity gain high-current amplifier, calculate: a) the settings from minimum to maximum calculate: a) the settings from minimum to maximum heat dissipation, and heat dissipation, and b) how the power varies with LSB b) how the power varies with LSB changes.changes.



DACDAC

SolutionSolution::DAC 10–V reference DAC 10–V reference 2 244 = 16 = 16

Therefore:Therefore:

1111 1111 (15/16) * 10 = 9.375 V (15/16) * 10 = 9.375 V

..

..

0000 0000 0 V 0 V

Amplifier gain = 24 / 9.375 = 2.56Amplifier gain = 24 / 9.375 = 2.56

Incremental step = [(1/16) * 10 ] * 2.56 = 1.6 VIncremental step = [(1/16) * 10 ] * 2.56 = 1.6 V

ΔV = (1/16) * 10 V



DACDAC

SolutionSolution::ΔΔP (from 0000 to 0001)P (from 0000 to 0001)

= (1.6 V)= (1.6 V)22 / 2 / 2 ΩΩ

= 1.28 W= 1.28 W

ΔΔP (from 1110 to 1111)P (from 1110 to 1111)

= (24)= (24)22 – (22.4) – (22.4)

22 / 2 / 2

= 37.12 W= 37.12 W

0

50

100

150

200

250

300

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Power (W)

Control Ward


7: Final Control7: Final ControlSignal ConversionsSignal Conversions Pneumatic SignalsPneumatic Signals

Pressure signal travels down the pipe at a speed in Pressure signal travels down the pipe at a speed in the range of the speed of sound.the range of the speed of sound.




Amplifier (booster or relay)Amplifier (booster or relay)




Amplifier (booster or relay)Amplifier (booster or relay) Nozzle/Flapper systemNozzle/Flapper system




Amplifier (booster or relay)Amplifier (booster or relay) Nozzle/Flapper systemNozzle/Flapper system Current-to-Pressure convertersCurrent-to-Pressure converters


7: Final Control7: Final ControlIndustrial ElectronicsIndustrial Electronics Silicon-Controlled Rectifier (SCR)Silicon-Controlled Rectifier (SCR)

Maximum forward currentMaximum forward current Peak reverse voltagePeak reverse voltage Trigger voltageTrigger voltage Trigger currentTrigger current Holding currentHolding current

Anode

Cathode

Gate


7: Final Control7: Final ControlIndustrial ElectronicsIndustrial Electronics

SCR Operation:SCR Operation:

Half-waveHalf-wave



SCR Operation:SCR Operation:

Full-waveFull-wave



SCR Operation: Full-wave (with digital control)SCR Operation: Full-wave (with digital control)



220 V50 Hz

V

L

N

Z

10 K

R VC

0.12 uF

SCR ExampleSCR ExampleAn SCR with a 4.0–V An SCR with a 4.0–V trigger is used as a trigger is used as a light–dimmer control. light–dimmer control. What resistance, R, What resistance, R, should be used to should be used to provide approximately provide approximately 10% to 90% ON 10% to 90% ON time?time?



220 V50 Hz

V

L

N

Z

10 K

R VC

0.12 uF

SCR ExampleSCR Example


7: Final Control7: Final ControlIndustrial ElectronicsIndustrial ElectronicsSCR ExampleSCR Example

VVCC(t) = V(t) = VOO(1 – e(1 – e-t/RC-t/RC))

4.0 = 10 (1 – e4.0 = 10 (1 – e-t/RC-t/RC))

t = 0.511 RCt = 0.511 RC

T T half a cyclehalf a cycle = 10 ms = 10 ms

10% 10% 1 ms 1 ms

90% 90% 9 ms 9 ms

With C = 0.12 With C = 0.12 μμFF

RRminmin = 16.3 K = 16.3 KΩΩ

RRmaxmax = 147 K = 147 KΩΩ

220 V50 Hz

V

L

N

Z

10 K

R VC

0.12 uF


7: Final Control7: Final ControlIndustrial ElectronicsIndustrial Electronics TRIACTRIAC Anode 2

Anode 1

Gate

DIACDIAC


7: Final Control7: Final ControlIndustrial ElectronicsIndustrial Electronics TRIACTRIAC

L

N

R

C

CV



TRIAC ExampleTRIAC ExampleAn DIAC with a 28–V An DIAC with a 28–V breakdown voltage is breakdown voltage is used in the light–used in the light–dimmer control. What dimmer control. What resistance, R, should resistance, R, should be used to provide be used to provide approximately 10% to approximately 10% to 90% ON time?90% ON time?

L

N

R

C

10 K

VZ

40 V



TRIAC ExampleTRIAC ExampleWhen does VAC reach 28 Volts so that it becomes possible to trigger the TRIAC?

L

N

R

C

10 K

VZ

40 V

)2*50(sin2*220 tVAC

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



TRIAC ExampleTRIAC Example

L

N

R

C

10 K

VZ

40 V)1( /RCt

ZC eVV

28 = 40 [ 1 – e – t / RC ]t = 1.2 RC

If t = 1 ms: RIf t = 1 ms: Rminmin = 6.9 K = 6.9 KΩΩ

If t = 9 ms: RIf t = 9 ms: Rmaxmax = 62.5 K = 62.5 KΩΩ


7: Final Control7: Final ControlActuatorsActuators Electrical ActuatorsElectrical Actuators

SolenoidSolenoid



SolenoidSolenoid DC MotorDC Motor AC MotorAC Motor



SolenoidSolenoid DC MotorDC Motor AC MotorAC Motor Stepping MotorStepping Motor




Pneumatic ActuatorsPneumatic Actuators




Pneumatic ActuatorsPneumatic Actuators

Hydraulic ActuatorsHydraulic Actuators


7: Final Control7: Final ControlControl ElementsControl Elements MechanicalMechanical

Solid-Material Hopper ValvesSolid-Material Hopper Valves


7: Final Control7: Final ControlControl ElementsControl Elements MechanicalMechanical

Paper ThicknessPaper Thickness


7: Final Control7: Final ControlControl ElementsControl Elements ElectricalElectrical

Motor Speed ControlMotor Speed Control


7: Final Control7: Final ControlControl ElementsControl Elements ElectricalElectrical

Temperature ControlTemperature Control


7: Final Control7: Final ControlControl ElementsControl Elements Fluid ValvesFluid Valves


7: Final Control7: Final Control

End of Chapter 7End of Chapter 7

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

Documents

ma control signal

converted control signal

final control objective

amp slide

lowenergy control signals

w power w control ward

vin v vout

ma v volts