1. ITT CET Capstone Project
PLC Based
Tank Fill Control System
Utilizing
Single feedback Control
Denis P. Cote

2. System Overview
Features
Tank Fill Control System
Allen Bradley SLC-500 PLC
Single Feedback – Strain Gauge Load Beam
Load Cell Signal Conditioning Amplifier
Ladder Logic

3. Overview
Program 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

4. System Diagram
Mechanical Layout
Water Tank
TK-1
SV
Load Cell
Suction
SV
Fill Valve 1
Supply Valve 2
5%
100%
Pump Recirc Valve
Pump
MOT

5. PLC Tank Fill System Diagram
Single 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:3/1
Fill Valve 1
Drain Valve 2
Pump MotorTK-1

6. Control Device List
Allen 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)

7. Feedback Sensor
Cantilever Load Beam
Strain Gauges
Half Bridge
Configuration
Applied Load, F
(i.e., Tank Weight)
Fixed End
9.125”
1”
.250”
F
Tension
Compression

8. 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

9. Signal Conditioning Schematic

10. Performance Data
Load 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)
AppliedLoad(Lbf)
Field Calibration 0 - 5 Lbs = 0 - 100% tank capacity
Known Weights Applied to Cell

11. Set Point Input
Potentiometer
INA128
Instrumentation
Amp IC
OPA177
OP Amp IC
Strain
Bridge Ckt
TP1
Output
Signal Conditioning Amplifier
Circuit Breadboard

12. Signal Conditioning Amplifier
Field Calibration / Proof of Concept

13. Ladder Logic

14. Back Up

15. Load Cell

16. Signal Conditioning Schematic
Component 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