Power Control System for a
Concrete Durability Test Cabinet
Project ID: May08-34
Group Members:
Matt Griffith, EE
Lindsay Spring, EE
Laron Evans, EE
Client:
National Concrete Testing Center
Manager: Bob Steffes
Faculty advisor:
Dr. Gregory Smith
DISCLAIMER: This document was developed as part of the requirements of an electrical and computer engineering
course at Iowa State University, Ames, Iowa. The document does not constitute a professional engineering design
or a professional land surveying document. Although the information is intended to be accurate, the associated
students, faculty, and Iowa State University make no claims, promises, or guarantees about the accuracy,
completeness, quality, or adequacy of the information. Document users shall ensure that any such use does not
violate any laws with regard to professional licensing and certification requirements. Such use includes any work
resulting from this student-prepared document that is required to be under the responsible charge of a licensed
engineer or surveyor. This document is copyrighted by the students who produced the document and the
associated faculty advisors. No part may be reproduced without the written permission of the senior design
course coordinator.
December 5, 2007
1
Table of Contents
Table of Contents
2
Table of Terms
3
Table of Figures
4
Chapter I: Project Plan
Current Situation
5
Problem
5
Customer Need Statement
5
System Block Diagram
6
New System Description
6
Operating Environment
6
Functional Requirements
6
Non-functional Requirements
7
Market Research
7
Deliverables
7
Work Breakdown Structure
8
Project Resources
11
Resource Requirements
12
Project Schedule
13
Signature Page
14
Chapter II: Project Design
15
Design Method
16
Option 1: Design A
17
Option 1: Design B
21
Option 2: Design A
24
Option 2: Design B
26
System Schematic
29
System Wiring Diagram
30
Advantages/Disadvantages
31
2
Team Recommendation
32
Table of terms
Term
Description
SPST
IC
RS 485
RS 232
PID
DIN
MODBUS
ASCII
Single Pole Single Throw. Like a light switch either open or closed.
Integrated circuit. A small chip that has a complex circuit on it.
Is a type of connector like an Ethernet plug or serial port.
A common port on most computers.
Proportional integrate and derivative control. A general class describing control circuitry.
A circular cable end with multiple pins. Like a mouse or keyboard connector.
An industry standard serial communications protocol.
American Standard Code for Information Interchange. A way to turn letters and symbols
in to decimal numbers.
Printed Circuit Board
PCB
3
Table of Figures
Figure
1
2
3
4
5
6
7
8
9
10
Description
Functional block diagram
Option 1 Design A system block diagram
Option 1 Design A wiring diagram
Option 1 Design A wiring diagram exploded view
Option 1 Design B scale drawing of temperature probe
Option 1 Design A system block diagram
Option 1 Design B system block diagram
Existing system schematic
Existing system wiring diagram
Sample computer user interface.
4
Current Situation
The National Concrete Testing Center, located in the Town Engineering building, uses a
Humboldt H-3185 rapid freeze-thaw cabinet to perform the ATSM C-666 test. It is controlled
by a Johnson Controls A72 temperature controller. The temperature recorder is a Supco
CR87B. The goal of the current system is to automatically run the C-666 test for about 300
cycles without incident.
Problem
The problem is the current system can’t perform the C-666 test within specifications
(documentation included p.asdf). The current control and data recording systems for the test
cabinet are not able to perform consistently. Sometimes it isn’t possible to get the concrete
samples down to 0°F or up to 40°F. If the test can’t be done consistently then the test cabinet
is of little value. Without further testing it isn’t possible to determine if the problem is with the
temperature control or with the data recording system or with both.
Customer Need Statement
A completely new system must be implemented to control the heat-cool cycle, and to record
the resulting temperatures. The specifications are as follows.





The heat-cool cycle must be automatically recorded by a computer with the use of
National Instrument's LabVIEWTM.
The data must be displayed on the computer screen as well as recorded to an Excel
spreadsheet.
The user interface must be digitally controlled via an on-site computer.
The heat-cool cycle must be constant for days at a time without adjustment.
The system must be scalable to allow the control of both machines in the lab.
5
System Block Diagram
New System Description
The new system will have a temperature input and a control signal output. The input signal will
be the voltage across a thermocouple placed inside one of the concrete blocks in the cabinet.
The voltage from the thermocouple will be digitized by the NI USB-6008. Once the
temperature data is read into the computer we will be able to use a program written with
LabVIEW to decide if the compressor or heating elements should be turned on. For example if
the compressor should be on then the USB-6008 will output a 10V signal which will actuate a
relay sending 120 VAC to the compressor turning it on.
Operating Environment
The system will operate in an indoor laboratory. We can assume that the room will be kept at
normal room temperature. The system will have to operate in dusty and possibly wet
conditions. Optimally the system should be mounted under the cabinet to minimize risk.
Functional Requirements
FR 1. The freezing-thawing apparatus shall have automatic controls which are able to
continuously reproduce cycles from 0±3°F to 40±3°F.
FR 2. If the control fails it shall fail in a frozen condition.
FR 3. The temperature sensor shall be able to sample various points within cabinet.
FR 4. The heat-cool cycle shall take between 2-5 hours.
FR 5. The time between freezing and thawing phases shall not exceed 10 minutes.
6
FR 6. The new system shall operate completely separate from the old system.
FR 7. All of the temperature data shall be recorded to an excel spreadsheet.
Non-Functional Requirements
NFR 1. All of the electrical components shall be housed in a waterproof enclosure.
NFR 2. The system shall not cause any fire hazards.
NFR 3. The system shall not cause any electrical shocks.
NFR 4. The user interface shall show a temperature vs. time graph that is open at all times
during testing.
Market Research
The company ScienTemp offers a very similar system. Their system contains the following
features:
 Touch-screen interface
 On/Off/Auto switch
 On/Off light indicators
 Cycle counter
 Safety interlocks and alarms
 Dedicated computer
There is also the company Humboldt who produces rapid freeze-thaw cabinets that is the same
as the current system of this project. Humboldt provides freeze-thaw cabinets with 115V or
230V power rating, 50Hz or 60Hz frequency, and single phase. They also provide heating
elements, stainless steel sample positioning tray, recording thermometer chart paper, and other
accessories necessary and compatible with the system.
The company Veriteq produces a precision temperature data logger, Spectrum 1000, which has
internal sensors, memory and a 10-year lifetime. It has a software package that enables realtime monitoring over an Ethernet network. It is also said to be durable and accurate under cold
conditions; its operating range is -40 degrees C to 85 degrees C. It will accept any 100 K ohm
thermistor probe compatible with Betatherm 100K6A1.
There are temperature controllers by Delta and Red Lion that are specifically designed to
control heating and cooling processes. The power supply needed for the temperature
controllers are 100-240VAC. Its input options are an analog, RTD, or thermocouple input. It
can be designed for 2-4 outputs and the options are relay, transistor, pulse voltage, and/or
linear voltage or current. It includes MODBUS communications, PID control programs, and
auto-tuning.
7
Deliverables







A computerized system that automatically controls the freeze-thaw cycle
A sufficient user-interface that allows lab users to input and analyze data
Two system operation; electromechanical or computerized control
More accurate temperature sensing; two or three temperature sensors
Ability to switch system operation
Automatic system error adjustments
Manual for future reference
8
Work Breakdown Structure
Complete
Task Name
X
Project Planning
X
Planning Presentation
X
Plan Review
X
Create Website
X
Retrieve LabVIEW
X
Learn LabVIEW
Project Design
X
Design LabVIEW User Interface
Design/Build System
X
Design Power Supply
X
Design Input Sensing and Controls
X
Design Output Controls
X
Design New Relay Control integration
X
Design Switch Control integration
X
Design Thermocouple Amplifier
X
Design Communications Scheme
Design System Location/Mounting
Finalize System Design
X
Design Presentation
Design Review
Install Relay
Install switch
Integrate New System
Test System Integration
Incomplete
% Completion
X
90%
X
50%
X
X
70%
90%
X
X
X
X
X
90%
N/A
N/A
N/A
N/A
9
The project will have the following work breakdown:








Project Planning
Plan Review
Create Website
Project Design
o Design LabVIEW User-Interface
o Design/Build System
 Design Power Supply
 Design Input Sensing and Controls
 Design Output Controls
 Design New Relay Control integration
 Design Switch Control integration
 Design Thermocouple Amplifier
 Design Communications Scheme
 Design System Location/Mounting
o Finalize System
o Design Presentation
o Design Review
Install Relay
Install Switch
Integrate New System
Test system
Individual and Dual Tasks
Lindsay Spring:
Design Input Sensing and Controls
Design System Location/Mounting
Design Switch Control integration
Install Switch
Design Communications Scheme
System test/diagnosis
Laron Evans:
Design Power Supply
Design Output Controls
Design System Location/Mounting
Design New Relay Control integration
System test/diagnosis
Matt Griffith:
Design LabVIEW user-interface
Design Input Sensing and Controls
Design New Relay Control integration
Install Relay
Design Thermocouple Amplifier
System test/diagnosis
10
Project Resources
Project Resources
Laron Evans
Project Engineer
Team Lead
Greg Smith
Project Advisor
Course
Coordinator
Power Control System for
Concrete Durability Test Cabinet
May08-34
Bob Steffes
Client
Lindsay Spring
Project Engineer
Comm. Coor.
Matt Griffith
Project Engineer
Diana Gualillo
Management
Consultant
11
Resource Requirements
Resources are engineers Lindsay Spring, Laron Evans, and Matt Griffith. The faculty advisor is
Dr. Greg Smith and the management consultant is Diana Gualillo. The client resource is Bob
Steffes. Each engineer has been assigned tasks that will contribute to completing the project on
time. Engineers will roughly work 190 to 200 hours to complete the project. The following
calculations are from assigning engineer resources to tasks:
Hours:
Lindsay Spring: 192
Laron Evans: 206
Matt Griffith: 192
Project Labor Cost
Lindsay Spring:
Laron Evans:
Matt Griffith:
$1,920
$2,060
$1,920
Materials Cost
Electromechanical Relay, 30A:
Solid-State Relay, 30A
Control Switch:
Power Supply, 15V, 1A:
Thermocouple, K-type, -330 to 2200 F:
Misc.:
$30
$50
$5
$15
$39.50
$20
Total Costs:
Total Cost minus labor:
$6059.5
$159.50
12
13
Power Control System for a
Concrete Durability Test Cabinet
Project: May08-34
Faculty advisor, client, and engineers please sign, print and date below indicating that you have
read and approve the project plan
Sign
Print
Date
X_________________________ X__________________________
X_______
X_________________________ X__________________________
X_______
X_________________________ X__________________________
X_______
X_________________________ X__________________________
X_______
X_________________________ X__________________________
X_______
14
Power Control System for a
Concrete Durability Test Cabinet
Final Design
Project ID: May08-34
Group Members:
Matt Griffith, EE
Lindsay Spring, EE
Laron Evans, EE
Client:
National Concrete Testing Center
Manager: Bob Steffes
Faculty advisor:
Dr. Gregory Smith
DISCLAIMER: This document was developed as part of the requirements of an electrical and computer engineering
course at Iowa State University, Ames, Iowa. The document does not constitute a professional engineering design
or a professional land surveying document. Although the information is intended to be accurate, the associated
students, faculty, and Iowa State University make no claims, promises, or guarantees about the accuracy,
completeness, quality, or adequacy of the information. Document users shall ensure that any such use does not
violate any laws with regard to professional licensing and certification requirements. Such use includes any work
resulting from this student-prepared document that is required to be under the responsible charge of a licensed
engineer or surveyor. This document is copyrighted by the students who produced the document and the
associated faculty advisors. No part may be reproduced without the written permission of the senior design
course coordinator.
December 5, 2007
15
Design Method
Functional Decomposition
Figure 1
Input Specification
Output Specification
The system has one
temperature input ranging
from 0o to 40oF.
The design will have one SPST relay output which will control
the heating and cooling elements in the existing system.
Design
Design A
Design B
Option 1: NI 6008
Thermocouple
Analog temperature IC
Option 2: Delta temp controller
RS 485 to RS 232 to computer
Analog Voltage to NI 6008 to
computer
16
Option 1: Design A
Design A: Use a thermocouple and thermocouple amplifier to send an analog voltage to the
NI 6008. Use LabVIEW to make the control decisions. Use the digital output
powered by an amplifier to switch a relay connected to the existing system.
If we choose to implement design A using a thermocouple as the temperature sensor the
𝟐𝟎 𝝁𝑽
output voltage will be about 𝐝𝐞𝐠 𝑭 , which is much smaller than the voltage sensitivity of the NI
6008 (138 mV). Therefore, a thermocouple conditioner along with an additional amplifier will
be required. The digital output of the NI 6008 is 8.5 mA which is not sufficient to power the
relay (40 mA), so a current amplifier will be needed. All of the electronic components will be
placed on an external PCB powered by a wall mount AC to DC converter. The computer will
be connected via USB to the NI 6008. Below is a block diagram for design A.
Figure 2
Option 1 Design A: Hardware Specifications
NI 6008 Specifications:
 8 analog inputs
 voltage range -10V to 10V
 sensitivity 138 mV
 2 analog outputs:
17


 voltage range -10V to 10V
 output current 5 mA
12 digital I/O 0-5V
 output current 8.5 mA
Compatible with LabVIEW
Thermocouple Specifications:
 Provided by client Bob Steffes:
 Make: OMEGA
 Model: PP-T-24-SLE
 Type: T
 Insulation: Polyvinyl
 Wire Type: Solid Wire
 Wire Gage: 24 AWG
 Max Temperature: 221ºF, 105ºC
Thermocouple Conditioner Specifications:
 Model: AD595
 Supply voltage of 5V to 30V
 Gain of 262
 10 mV/°C sensitivity
Amplifier Specifications:
 Supply voltage of 2.7V to 5.25V
 Gain of 40
 Opterating temperature -40oC to 100oC
Control Relay Specifications:
 Model: G5C-14-DC5
 Type: SPST
 Contact rating of 15A at 125V
 Coil rating at 5VDC at 200mW
Power Supply Specifications:
 Model: WM063-1950-D5
 5V, 12V, -12V
 .6A, 0.16A, 0.16A
 6.3 Watts
Transistor Specifications:
 Model: DTC114GSA
 Collector-Emitter voltage max 50V
 Emitter-Base voltage max 5V
 Collector current 100 mA
18

Max temperature 150oC
Manual Switch Specifications:
 Make: GC
 Model: 35-110
 Type SPDT
 Current rating 20A 125V
Wiring Diagram
Figure 3
19
External Hardware
Figure 4
Component Specifications:
Thermocouple
Conditioner
Amplifier
Relay
Power Supply
transistor
USB repeater
Cat 5 Cable
PCB and Case
Manual Switch
Make
Analog Devices
Model
AD595
Cost
$6.18
Texas Instruments
Omron Electronics
Elpac
LPV321
G5C-14-DC5
WM063-1950D5
DTC114GSA
Super Booster
$1.04
$3.98
$41.00
ROHM
Cables to Go
100’
Team Manufactured
GC
35-110
$0.46
$84.24
$18.26
$50
$3.32
Total Cost Approximation:
Computer less than 15ft from freeze-thaw machine $105.98
Computer less than 150ft from freeze-thaw machine $208.48
Issues:
This is a custom design that will need to be supported.
20
Option 1: Design B
Design B: Using an IC temperature probe instead of a thermocouple.
If we choose to implement design B using an IC temperature probe and amplifier, the design
would require a large amount of custom design and building. The analog IC temperature
sensor and an amplifier would be housed inside of a 6” stainless steel probe. It would require
using thermal adhesive to attach the sensor to the tip of the probe, and silicone adhesive to
secure the amplifier. The rest of the design would be the same as in A; the only difference
would be the type of temperature sensor used. A scale drawing of the probe is on the
following page.
21
Figure 5
22
NI 6008 Specifications:
 8 analog inputs
 voltage range -10V to 10V
 sensitivity 138 mV
 2 analog outputs:
 voltage range -10V to 10V
 output current 5 mA
 12 digital I/O 0-5V
 output current 8.5 mA
 Compatible with LabVIEW
Amplifier Specifications:
 Supply voltage of 2.7V to 5.25V
 Gain of 40
 Opterating temperature -40oC to 100oC
Control Relay Specifications:
 Model: G5C-14-DC5
 Type: SPST
 Contact rating of 15A at 125V
 Coil rating at 5VDC at 200mW
LM235a Analog Temperature Sensor:
 Temp range -40oC to 100oC
 1oC accuracy
 Linear output
 10 mV/ oC
 5V supply voltage
Transistor Specifications:
 Model: DTC114GSA
 Collector-Emitter voltage max 50V
 Emitter-Base voltage max 5V
 Collector current 100 mA
 Max temperature 150oC
Manual Switch Specifications:
 Make: GC
 Model: 35-110
 Type SPDT
 Current rating 20A 125V
23
Component Specifications:
Temp sensor
Relay
transistor
Make
National Semiconductor
Omron Electronics
ROHM
Model
LM235a
G5C-14-DC5
DTC114GSA
Cost
$0.89
$3.98
$0.46
USB repeater
Amplifier
Cables to Go
Texas Instruments
Super Booster
LPV321
$84.24
$1.04
Steel Probe
Pressure fitting
Thermal Adhesive
Silicone Adhesive
Cat-5 cable
Cap
Manual Switch
Omega
Omega
Arctic Silver
GE
100’
Anderson Barrows
GC
SS-38
SSLK-38-38
AATA-5G
GE284
$8.50
$18.00
$5.99
$3.44
$18.26
$1.28
$3.32
PB61CP
35-110
Total Cost Approximation:
Computer less than 15ft from freeze-thaw machine $46.90
Computer less than 150ft from freeze-thaw machine $149.40
Issues:
Custom design will be required to build the sensor and its case. We aren’t sure how long it
would take to make the probe, and that isn’t our area of expertise.
Option 2: Design A
Design A: Using the DELTA temperature controller for control. Temperature data will be
sent to the computer using a RS 485 to RS 232 converter.
If we choose to implement design 2A the controller will use PID control to switch the relay
output which will be connected to the existing system. The controller will be able to
automatically cycle from 0 to 40 degrees F. Temperature data will be logged using LabVIEW.
24
Figure 6
DELTA Temperature Controller Specifications:
 Dual outputs
 PID, ON/OFF, Manual, and PID programmable control
 PID and Auto-Tuning
 Two built-in control output (for heating/cooling control), and alarm output
 Output options: Relay (250VAC, 5A max), DC Current (4-20mA), or Linear Voltage (05V, 0-10V)
 RS-485 (MODBUS ASCII/RTU) communication
 One Thermocouple sensor input (all types)
 DIN rail mounting
 Interface programming
 100-240V supply, 50-60Hz
Thermocouple Specifications:
 Provided by client Bob Steffes:
 Make: OMEGA
 Model: PP-T-24-SLE
 Type: T
 Insulation: Polyvinyl
 Wire Type: Solid Wire
25



Wire Gage: 24 AWG
Wire Accuracy: Special Limits of Error
Max Temp: 221oF, 105oC
RS232/484 Converter Specifications:
 CommFront Technologies
 Port-powered, no external power required
 Data direction auto-turnaround, no flow control is required
 Dimensions (H x W x D): 0.63 x 1.3 x 3.4 in
Manual Switch Specifications:
 Make: GC
 Model: 35-110
 Type SPDT
 Current rating 20A 125V
Component Specifications:
Make
Model
Cost
Temperature Controller
Cat-5 cable
DELTA
100’
DTB4848-
$90
$18.26
Thermocouple
RS232/484 Converter
Omega
CommFront Technologies
PP-T-24-SLE
CVT-485-1
Provided
$60.90
Manual Switch
GC
35-110
$3.32
Total Cost Approximation: $172.48
Option 2: Design B
Design B: This would be a worst case scenario for the Delta temp controller. This design
would just use the linear voltage output of the temperature controller like the thermocouple
conditioner and amplifier. We are considering this possibility because having just a single order
PID controller might not be enough to provide adequate control of the system. This design
would use the temperature controller to sense the temperature and use the NI 6008 for all of
the control decisions. Below is a wiring diagram for design 2B.
26
Figure 7
NI 6008 Specifications:
 8 analog inputs
 voltage range -10V to 10V
 sensitivity 138 mV
 2 analog outputs:
 voltage range -10V to 10V
 output current 5 mA
 12 digital I/O 0-5V
 output current 8.5 mA
 Compatible with LabVIEW
Thermocouple Specifications:
 Provided by client Bob Steffes:
 Make: OMEGA
 Model: PP-T-24-SLE
 Type: T
 Insulation: Polyvinyl
27



Wire Type: Solid Wire
Wire Gage: 24 AWG
Max Temperature: 221ºF, 105ºC
Control Relay Specifications:
 Model: G5C-14-DC5
 Type: SPST
 Contact rating of 15A at 125V
 Coil rating at 5VDC at 200mW
Transistor Specifications:
 Model: DTC114GSA
 Collector-Emitter voltage max 50V
 Emitter-Base voltage max 5V
 Collector current 100 mA
 Max temperature 150oC
DELTA Temperature Controller Specifications:
 Dual outputs
 PID, ON/OFF, Manual, and PID programmable control
 PID and Auto-Tuning
 Two built-in control output (for heating/cooling control), and alarm output
 Output options: Relay (250VAC, 5A max), DC Current (4-20mA), or Linear Voltage (05V, 0-10V)
 RS-485 (MODBUS ASCII/RTU) communication
 One Thermocouple sensor input (all types)
 DIN rail mounting
 Interface programming
 100-240V supply, 50-60Hz
Manual Switch Specifications:
 Make: GC
 Model: 35-110
 Type SPDT
 Current rating 20A 125V
Temperature Controller
Cat-5 cable
transistor
USB repeater
Make
DELTA
100’
ROHM
Cables to Go
Thermocouple
Omega
Model
DTB4848DTC114GSA
Super
Booster
PP-T-24-SLE
Cost
$90
$18.26
$0.46
$84.24
Provided
28
Manual Switch
Relay
GC
Omron Electronics
35-110
G5C-14-DC5
$3.32
$3.98
Total Cost Approximation:
Computer less than 15ft from freeze-thaw machine $97.76
Computer less than 150ft from freeze-thaw machine $200.26
Connection to the existing system
Figure 8
29
Wiring diagram
Figure 9
Software Specification
The PC operating system will run on Microsoft version XP and the LabVIEW will run on a
version of no less than 8.0.
User Interface Specification
The user interface will be controlled through a PC computer using LabVIEW software that will
collect the temperature data and record it into an Excel spreadsheet.
The following image shows an example of the LabVIEW user interface.
30
Figure 10
Advantages and Disadvantages
Option 1 Design A:
Thermocouple
Option 1 Design B:
Analog Temperature
IC
Option 2 Design A:
RS 485 to RS 232 to
Computer
Option 2 Design B:
Analog Voltage to NI
6008 to computer
Advantages
Design and fabrication
within our scope. Easy to
write the software.
Disadvantages
We would have to make
custom circuits and PCBs.
External power supply.
Cost
Computer
< 15ft $105.98
Computer
< 150ft $208.48
If we make multiple probes
they would be easy to
replace. No external power
supply or PCB. Easy to write
the software.
No custom circuits. Delta
would provide customer
support. Same cost for the
computer close or far.
No custom circuits or PCB.
Varity of possible
combinations. Easy to write
the software.
Fabrication would be
difficult. Little support for
probe.
Computer
< 15ft $46.90
Computer
< 150ft $149.40
Only first order PID
control.
$172.48
Computer
< 15ft $97.76
Computer
< 150ft $200.26
31
Team Recommendation
Based on the above three design choices, the team recommendation is for Option 2 Design A,
using the DELTA temperature controller. Based on the advantages, it appears that it will be the
most cost effective design with minimal custom build therefore requiring minimal support. Also
if the controller is unable to perform it would only take an additional $5.00 to change to Design
B using the NI 6008. Using the Delta temperature controller has the highest success rate and
the most flexibility.
32