ITT CET Capstone Project

PLC Based

Tank Fill Control System

Utilizing

Single feedback Control

Denis P. Cote

System OverviewFeatures

Tank Fill Control System

Allen Bradley SLC-500 PLC

Single Feedback – Strain Gauge Load Beam

Load Cell Signal Conditioning Amplifier

Ladder Logic

OverviewProgram Operation

User setpoint: 5 – 100% via input,

System activates via start PB #1,

Tank fill valve opens, pump starts

Tank fills to setpoint,

Pump stops, fill valve closes,

Tank drain valve opens after 10 seconds,

Tank drains to 5% level,

Tank drain valve closes, pump restarts, fill valve opens

Tank fills back to initial set point,

Process repeats; deactivates via stop PB #2

System DiagramMechanical Layout

Water Tank

TK-1

SV

Load Cell

Suction

SV

Fill Valve 1

Supply Valve 2

5%

100%

Pump Recirc Valve

Pump

MOT

PLC Tank Fill System DiagramSingle Loop Control

SV

SV

MOT

PLC

SLC-5/02

INPUTS

OUTPUTS

Tank Level

Set Point

Potentiometer

I:2.0

PC

Signal

Conditioner

Sensor

O:3/2

I:3.0

O:3/0

O:3/1Fill Valve 1

Drain Valve 2

Pump MotorTK-1

Control Device ListAllen Bradley SLC-5/02 CPU (Slot 0)

Input List

Load Cell I:3.0

Setpoint I:2.0

Modules

1746-IN4 Analog

Module (Slot 1)

1746-IA8 120VAC

Input Module (Slot 2)

Output List

Pump Motor O:3/0

Fill SV-1 O:3/1

Drain SV-2 O:3/3

Modules

1746-OA8 Relay Output Module (Slot 3)

Feedback SensorCantilever Load Beam

Strain Gauges

Half Bridge

ConfigurationApplied Load, F

(i.e., Tank Weight)

Fixed End

9.125”

1”

.250”

F

Tension

Compression

Feedback Circuit Diagram

+5VDC

Regulator

(7805)

AB

1746-IN4

Analog In

Module

INA128

Load Cell

Supply

Voltage

13-15V

-5VDC

Regulator

(7905)

OPA177

+12VDC

Regulator

(7812)

-12VDC

Regulator

(7912)

SLC-500

PLC

To Regulators

Signal Conditioning Schematic

Performance DataLoad Cell Calibration

Calibration Data

Measured Values

Applied Load Tank Level IA Output SG Output Counts

Lbf % V' Vo

0 0 0 0 -32

1 20 0.41 1.8 5878

2 40 0.82 3.59 11776

3 60 1.23 5.38 17646

4 80 1.65 7.17 23474

5 100 2.06 8.97 29380

Load Cell Calibration Curve

0

1

2

3

4

5

6

0 1 2 3 4 5 6 7 8 9 10

Output Volts (V)

Ap

plied

Lo

ad

(L

bf)

Field Calibration 0 - 5 Lbs = 0 - 100% tank capacity

Known Weights Applied to Cell

Set Point Input

Potentiometer

INA128

Instrumentation

Amp IC

OPA177

OP Amp IC

Strain

Bridge Ckt

TP1

Output

Signal Conditioning AmplifierCircuit Breadboard

Signal Conditioning AmplifierField Calibration / Proof of Concept

Ladder Logic

Back Up

Load Cell

Signal Conditioning SchematicComponent List

C1,3,5,7,9 220uF 50V electrolytic

C2,4,6,8,10 0.1uF 50V ceramic

D1 LED - Red

Rgauge 1,2 Strain Gauge Micro-Measurements CEA-13-187UW-350

350 ohm +/-0.3%, GF 2.145

R3,4 348 ohm, 1% tol. 1/4 watt metal film

R5,10 10K trimmer potentiometer

R6 1K 1/4 watt

R7 50.2 ohm, 1% tol. precision gain resistor

R8 5K trimmer potentiometer set to 2.955K

R9 10K 1% tol. 1/4 watt metal film

R11 100K 1% tol. 1/4 watt metal film

U1 INA128P precision, low power instrumentation amp - Texas Instruments

U2 OPA177 precision operational amp - Texas instruments

U3,4 LM7805 +5Vdc voltage regulator TO-220

U5 LM7812 +12Vdc voltage regulator TO-220

U6 LM7905 -5Vdc voltage regulator TO-220

U7 LM7912 -12Vdc voltage regulator TO-220