chapter 07 final control

3442Industrial Instruments 2

Chapter 7Final ControlDr. Bassam KahhalehPrincess Sumaya Univ.Electronic Engineering Dept.

3442 - Industrial Instruments 2

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


7: Final ControlOperationBlock DiagramSignalConversionsActuatorFinalControlElementProcessControlSignal


7: Final ControlOperationBlock DiagramSignalConversionsActuatorFinalControlElementProcessControlSignalThe 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.


7: Final ControlOperationBlock DiagramSignalConversionsActuatorFinalControlElementProcessControlSignalThe actuator is a translation of the (converted) control signal into action on the control element.


7: Final ControlOperationBlock DiagramSignalConversionsActuatorFinalControlElementProcessControlSignalThe control element is operated (run) by the actuator.


7: Final ControlOperationBlock DiagramSignalConversionsActuatorFinalControlElementProcessControlSignalThe process is operation (objective) under control.


7: Final ControlOperationExample: Baking of Crackers


7: Final ControlSignal ConversionsAnalog Electrical SignalsRelaysMechanicalSolid-State

AmplifiersTransistorOp-amp


7: Final ControlSignal ConversionsAnalog Electrical SignalsRelaysMechanical


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

7: Final ControlSignal ConversionsAnalog Electrical SignalsOp-ampExample:Convert a 4 20 mA control signal to a 5 10 V signal.Solution:Vin = Rin * IinVout = K Vin + VB


7: Final ControlSignal ConversionsAnalog Electrical SignalsOp-ampSolution:Vin = Rin * Iin

Let Rin = 100


I

V

in

in

R

7: Final ControlSignal ConversionsAnalog Electrical SignalsOp-ampSolution:Vout = K Vin + VB5 = K * 0.4 + VB10 = K * 2 + VBK = 3.125VB = 3.75Vout = 3.125 Vin + 3.75Vout = 3.125 (Vin + 1.2)


7: Final ControlSignal ConversionsAnalog Electrical SignalsOp-ampSolution:Vout = 3.125 (Vin + 1.2)


7: Final ControlSignal ConversionsDigital Electrical SignalsOp-ampDACDirect ActionExample:A 4-bit digital word is intended to control the setting of a 2- DC resistive heater. Heat output varies as a 0 24 V input to the heater. Using a 10V 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.


7: Final ControlSignal ConversionsDigital Electrical SignalsDACSolution:DAC 10V reference 24 = 16Therefore:1111 (15/16) * 10 = 9.375 V . .0000 0 VAmplifier gain = 24 / 9.375 = 2.56Incremental step = [(1/16) * 10 ] * 2.56 = 1.6 VV = (1/16) * 10 V


7: Final ControlSignal ConversionsDigital Electrical SignalsDACSolution:P (from 0000 to 0001) = (1.6 V)2 / 2 = 1.28 WP (from 1110 to 1111) = (24)2 (22.4)2 / 2 = 37.12 W

Power (W)Control Ward


7: Final ControlSignal ConversionsPneumatic SignalsPressure signal travels down the pipe at a speed in the range of the speed of sound.


7: Final ControlSignal ConversionsPneumatic SignalsPressure signal travels down the pipe at a speed in the range of the speed of sound.Amplifier (booster or relay)


7: Final ControlSignal ConversionsPneumatic SignalsPressure signal travels down the pipe at a speed in the range of the speed of sound.Amplifier (booster or relay)Nozzle/Flapper system


7: Final ControlSignal ConversionsPneumatic SignalsPressure signal travels down the pipe at a speed in the range of the speed of sound.Amplifier (booster or relay)Nozzle/Flapper systemCurrent-to-Pressure converters


7: Final ControlIndustrial ElectronicsSilicon-Controlled Rectifier (SCR)Maximum forward currentPeak reverse voltageTrigger voltageTrigger currentHolding current


Anode

Cathode

Gate

7: Final ControlIndustrial ElectronicsSCR Operation:Half-wave


7: Final ControlIndustrial ElectronicsSCR Operation:Full-wave


7: Final ControlIndustrial ElectronicsSCR Operation: Full-wave (with digital control)


7: Final ControlIndustrial ElectronicsSCR ExampleAn SCR with a 4.0V trigger is used as a lightdimmer control. What resistance, R, should be used to provide approximately 10% to 90% ON time?


220 V50 Hz

V

L

N

Z

10 K

R

V

C

0.12 uF

50 W

7: Final ControlIndustrial ElectronicsSCR Example


220 V50 Hz

V

L

N

Z

10 K

R

V

C

0.12 uF

50 W

7: Final ControlIndustrial ElectronicsSCR ExampleVC(t) = VO(1 e-t/RC)4.0 = 10 (1 e-t/RC)t = 0.511 RCT half a cycle = 10 ms10% 1 ms90% 9 msWith C = 0.12 FRmin = 16.3 KRmax = 147 K


220 V50 Hz

V

L

N

Z

10 K

R

V

C

0.12 uF

50 W

7: Final ControlIndustrial ElectronicsTRIACDIAC


Anode 2

Anode 1

Gate

7: Final ControlIndustrial ElectronicsTRIAC


L

N

R

C

C

V

7: Final ControlIndustrial ElectronicsTRIAC ExampleAn DIAC with a 28V breakdown voltage is used in the lightdimmer control. What resistance, R, should be used to provide approximately 10% to 90% ON time?


L

N

R

C

10 K

V

Z

40 V

7: Final ControlIndustrial ElectronicsTRIAC ExampleWhen 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 periodAnd for 40 Volts:40 = 310 sin(314 t)t = 0.412 ms 4.1% of the period


L

N

R

C

10 K

V

Z

40 V

7: Final ControlIndustrial ElectronicsTRIAC Example

28 = 40 [ 1 e t / RC ]t = 1.2 RCIf t = 1 ms: Rmin = 6.9 KIf t = 9 ms: Rmax = 62.5 K


L

N

R

C

10 K

V

Z

40 V

7: Final ControlActuatorsElectrical ActuatorsSolenoid


7: Final ControlActuatorsElectrical ActuatorsSolenoidDC MotorAC Motor


7: Final ControlActuatorsElectrical ActuatorsSolenoidDC MotorAC MotorStepping Motor


7: Final ControlActuatorsElectrical ActuatorsSolenoidDC MotorAC MotorStepping MotorPneumatic Actuators


7: Final ControlActuatorsElectrical ActuatorsSolenoidDC MotorAC MotorStepping MotorPneumatic ActuatorsHydraulic Actuators


7: Final ControlControl ElementsMechanicalSolid-Material Hopper Valves


7: Final ControlControl ElementsMechanicalPaper Thickness


7: Final ControlControl ElementsElectricalMotor Speed Control


7: Final ControlControl ElementsElectricalTemperature Control


7: Final ControlControl ElementsFluid Valves


7: Final ControlEnd of Chapter 7


Princess Sumaya UniversityDr. Bassam Kahhaleh

chapter 07 final control

Documents

final control element

final controloperationexample

final controldr

converted control signal

ma control signal

vin vb5

lowenergy control signals

iinlet rin