Download BODY TEMPERATURE REGULATION FOR QUADRIPLEGIC

BODY TEMPERATURE REGULATION FOR
QUADRIPLEGIC WEARER
Team #1
Albert Alexander – Project Manager
Steven Shane –Web Master
Melissa Stroud –Document/Presentation Prep
Stephen Zajac –Lab Monitor/Parts Acquisition
Faculty Coordinator: Dr. R. J. McGough
Sponsored by:

Michigan State University Resource Center for Persons with Disabilities

Chrysler Foundation

Wochholz Endowment
Executive Summary
Spinal injuries can cause a disorder in which the body cannot properly regulate its
own temperature. Hot or cold weather causes large swings in core temperature, severely
impairing basic body functions. This disorder typically accompanies paralysis of the legs
or arms, leaving a person wheelchair-bound. In an effort to provide greater independence
and increased safety for people with this disability, we have designed a wheelchair
accessory which regulates body temperature. A network of tubes circulates temperaturecontrolled liquid through an all-weather garment, keeping the wearer’s core temperature
within a comfortable range. The garment is sewn into a starter jacket, maintaining the
appearance and comfort of an all-weather windbreaker, and sensor feedback provides
active diagnostics as well as a platform for future automation development. Most
importantly, every component of the system is built to last, and mechanical elements are
easily serviceable to ensure years of use. These features keep the wearer safe and allow
them a greater degree of mobility and freedom in a variety of environments.
Introduction/Background
Thousands of Americans live with the effects of spinal injuries. A subset of this
group contains people whose spinal injury has resulted in severely reduced circulation
and sensation in their limbs. Decreased sensation causes the body to become less able to
manage its own core temperature, which in turn increases the sensitivity of the body to
changes in the environment, a condition known as quadriplegic poikilothermia. For such
people, hypothermia and heat stroke are constant concerns when they are outside
People with poikilothermia often struggle to coexist with the outside weather,
particularly in places like Michigan, where extreme temperatures—hot and cold—are not
uncommon. While there are products available to help moderate body temperature, few
fit the unique needs of a poikilotherm. Resistive heating fabrics are imprecise and can be
dangerous, while medical silicone pads are maintenance-intensive and restrict mobility.
This unfilled need inspired the construction of a wheelchair accessory that is capable of
heating or cooling the wearer without compromising independence or mobility.
Much like electric blankets, conventional temperature-regulated clothing available
on the market uses resistive heating, in which a DC power source (usually a battery) runs
current through resistive wire distributed about the garment. However, resistive heating
in wires, unless carefully regulated, can result in thermal runaway, causing discomfort,
burns, or even fires. In addition, metals used in such resistive heating generally have high
specific heat, which results in uneven distribution of heat on the body. Such limitations
are particularly dangerous for poikilotherms, who may be unable to detect thermal
runaway until significant damage has already been done. It is not uncommon for such
devices to bear warning labels which say specifically, “not for use by quadriplegics.”
More sophisticated garments exist in which silicone pads in the garment are heated
resistively, but these are generally designed for bedside hospital care and include large,
stand-alone circulation systems that are very expensive and require periodic adjustment
by trained professionals.
Our design is unique in that it provides a simple and mobile means of controlling
temperature in both hot and cold environments. The device uses solid-state thermoelectric
technology to eliminate the need for a bulky compressor, providing a complete
temperature-control solution in a compact package that hangs on the back of the
wheelchair. With the completion of the project, wheelchair-bound people with
poikilothermia will be free to enjoy the outdoors regardless of the restrictions of their
disability.
Approach
Our solution to the problem is to use a Peltier Effect thermoelectric as the mode
of heating or cooling water, which will circulate throughout tubes incorporated into a
jacket that can be worn by the user. Several advantages follow from using this approach:
First and foremost, the Peltier Effect Thermoelectric (PETE) allows the water to be
heated or cooled using a single solid-state device instead of the large, noisy compressor
system typical in most other refrigeration applications. By comparison, the PETE is
silent, compact, and contains no moving parts, presenting limited opportunity for failure.
The water circulation system bypasses the problems associated with resistive
wiring. Most notably, water experiences no thermal runaway, and its higher specific heat
ensures that the exchange of heat will take place across the whole length of the tubes
instead of within the first few feet only.
Technical Work
The development of the final product is best considered when divided up into
discrete systems.
Thermal System
The thermal system is composed of three separate parts: Thermoelectric, and heat
exchange.
The thermoelectric device used in this project is a Peltier Effect Thermoelectric
Junction (PETE) as mentioned above. PETE are usually used in cooling applications
where a compressor would be too large, noisy, or otherwise impractical. The unique
aspect of the PETE is that it can be made to pump heat to or away from a surface
depending only on the polarity of the voltage. Thus, heating and cooling are both made
possible with a single device without any need for moving parts beyond a simple dualthrow relay to manage the polarity of the voltage. Furthermore, the PETE is compact,
solid-state, and silent.
Since the PETE is a heat pump, a significant heat sink had to be installed on the
thermoelectric to prevent a high temperature differential buildup between the two sides,
as a high differential saps the efficiency of heat transport. The PETE also dissipates a
significant amount of heat in the course of regular operation, a byproduct of its relatively
low efficiency.
The sinking scheme for the thermoelectric uses two 12V electric fans to pass air
through a commercial nickel-plated copper heat sink. The heat sink is bonded directly to
one side of the thermoelectric. Even at full operation in cooling mode, the heat sink does
not noticeably increase in temperature over time, ensuring a low differential, and thus
greater efficiency.
Heat is transferred through a commercial water block between the thermoelectric
and the water circulated through the tubing. A combination of thermal grease and the
heavy-duty ceramic coating on the PETE guards against stray charge or current finding
its way into the water while maximizing heat exchange.
Power System
In any electrical engineering project, power is a vital concern. Managing the flow
of power through the circuitry linked to the actuators is what drives the functionality of
the product as a whole.
The system is designed to run on 24V, the standard voltage for electric wheelchair
batteries. Three pin XLR connections run the power from the battery to the case, with
female connections on the powered side to avoid shorting a hot pin. Within the case,
switched power supplies and PWM control deliver voltage and wattage appropriate for
each of the four main electrical components in the system: the cooling fans, the
thermoelectric device (PETE), the pump, and the microchip control system.
The PETE consumes up to 136W in regular operation. While the PETE is
compatible with a wide range of voltages, this particular junction pumps heat most
efficiently at 17V. At 17V, the PETE will draw up to 8A of continuous current for many
minutes at a time. Drawing this much current brings up special concerns for mounting
and isolation. The power from the battery is run directly to the switched power supply for
the PETE using 12ga wire. The switched power supply is wired point-to-point and is
grounded directly to the star ground for the case.
When considering the efficiency of a DC-DC switcher there are four main sources of loss
in the system: on resistance of the transistor, voltage drop across the diode, winding
resistance of the inductor, and equivalent series resistance (ESR) of the capacitor. On
resistance of the transistor was minimized by using an Insulated Gate Bi-Polar transistor
(IGBT) which has an on resistance of 2 milliohms. Assuming the maxium amount of
current flowing through the transistor is 10A, resistive heating due to I2R losses will be at
most 2 tenths of a watt. This is small enough to eliminate the need to heatsink the device.
It causes isolation issues though that will be discussed ion the controls section. Diode
voltage drop was reduced by using a Schottky rectifier diode with a much smaller voltage
drop than traditional silicon diodes. The inductor value used was minimized to the
amount required for the circuit to operate properly since high inductance ratings translate
directly to more winding resistance. The capacitor value was also kept as low as
possible, since large electrolytic capacitors usually have very high ESR values.
A 15A fuse protects the entire system in case of a short, but after the 15A fuse
there is a separate 24V power run with a 6A fuse. This 6A fused circuit provides power
for the rest of the system, which runs at a much lower wattage than the thermoelectric.
Within this low amperage system block, A dedicated 5V switched-mode power supply
provides Vcc for the microcontroller at very high efficiency, keeping the idle current for
the system low to prolong battery life. The microcontroller is always on in order to run
active diagnostics, but the power consumption is only 100mA, basically insignificant
compared to the power drawn by the wheel motors.
Mechanical Elements
The case is constructed from 16ga aluminum, chosen for its light weight and
corrosion resistance. All edges and corners are folded over to increase rigidity. The
vertical air intake is located as far as possible from the circuitry to protect the electronics
from moisture. However, the air drawn downward by the two fans causes a negative
pressure differential, pulling air from holes in the far end of the case across the circuitry,
carrying heat away from the MOSFET switches. The circuit boards are mounted on
plexiglass above the pump and tube assembly, preventing shorts in case of a leak or a
spurting connection, and all external electrical connections are oriented straight
downward against the side of the case to prevent water damage and to keep the wires
from snagging or tangling. All internal board-to-board connections are run with amp
connectors and are color-coded by control element to facilitate easy troubleshooting and
connection/disconnection. High-amperage connections are run with heavy-gauge wire
and are either directly twisted and soldered or attached with heavy duty insulated spades
to prevent resistive heating at contacts, PCB damage, and accidental shorts.
MOSFET switches provide logic-level PWM control for two fans, a reciprocating
pump, and a DPDT relay which swaps the voltage polarity across the PETE, switching
between heating and cooling. All of these devices are run off of the 6A fused 24V power
rail.
Special factors were taken into consideration for each of the devices. For
example, the fans are designed for 12V and are wired in series; if one of the fans becomes
obstructed due to an air restriction, its impedance will increase, causing it to draw more
power than the other fan and equalizing airflow.
A reciprocating pump was chosen due to its high capacity for back pressure and
its compatibility with air bubbles. The pump, which was originally designed for 12V
control, has been modified to overcome the extreme flow restriction caused by 30 feet of
1/8” tubing. Its internal spring was replaced by a much stronger one, and the voltage was
increased to 24V, causing a larger amount of circulation for each thrust of the diaphragm.
In its final form, the pump is capable of moving up to 15 gallons per minute, providing a
very comfortable margin for the 5 gallons per minute minimum flow needed to maintain
a 10° differential between the jacket intake and outtake.
The relay is rated at 15A, making it more than capable of supporting 9A of
continuous draw at the absolute maximum drawn by the thermoelectric. Since the coil
draws a full 1.2W when engaged, the relay defaults to setting the PETE to cooling mode.
The PETE is much more efficient at heating than cooling since the resistivity of the
PETE creates heat in addition to the Peltier effect, so defaulting to cooling narrows the
efficiency gap between the two modes. In addition, defaulting to cooling mode is safer
than heating mode in the case of extreme malfunction. If somehow an electrical short
causes the thermoelectric to engage and the PSoC diagnostic system fails to turn it off,
cooling the user is merely inconvenient, while heating can cause heatstroke.
Circuit and Control Integration
The pump, fans, relay coil, and PETE are all controlled by logic-level output from
the PSoC. The pump, fans, and relay coil are all high-side drive, while the PETE is lowside drive to take advantage of the low on resistance of the n-channel driving circuit for
the switched mode power supply. All devices default to off when the PSoC is turned off.
This is achieved by using internal pull-up logic on the pump, fans, and relay coil, and
internal pull-down with an external pull-up resistor on the PETE. The pump, fans, and
relay coil are all driven by n-channel MOSFETs, providing complete isolation between
the output power and the PSoC logic. This isolation protects the PSoC from stray currents
on the inductive power output stages of each subcircuit. In order to electrically isolate
the PSoC digital control line from the thermoelectric DC-DC switcher, and opto-isolater
is used. This device contains an LED and a phototransistor in a single package, with a
light bridge in between the two elements. The control signal from the PSoC functions to
turn the led on and off, which will in turn cause the phototransistor to switch on and off.
It is this phototransistor that controls the n-channel mosfet switcher. The benefit here is
that there is complete electrical isolation between the PSoC and the DC-DC switcher.
Sensors
Thermistors are thermally-sensitive resistors with the ability to conduct electricity
controlled by temperature. Thermistors are divided into two different categories based
upon whether their resistance increases or decreases with a rise in temperature.
Negative Thermal Coefficient (NTC) thermistors are used as temperature measuring
devices and decrease proportionally with increases in temperature.
Thermistors are used in this project to monitor the temperature of three separate
areas, and the information is linked to the control system to provide valuable diagnostic
information. Temperature sensors monitor the output of the heat exchanger, the
temperature of critical heat sinks within the case, and the air inside the jacket worn by the
customer.
Omega 44006 precision thermistors (10kΩ @25C) were
5V DC
used in this project, because thermistors can be used with long
44006 Thermistor
extension leads with a small loss of accuracy with ±.2deg C or
To Control System
±.1deg C interchangeability tolerance. Furthermore, thermistors
10kOhm (.1% tol)
are usually more accurate than thermocouples and although have a
limited temperature range because of their non-linearity, since the
temperature range in our application is low by comparison, thermistors are particularly
suited to the application. Thermistors also have a fast response time and are better suited
for precision temperature measurements. Thermistors tend to be smaller and more rugged
than RTD’s or thermocouples. The resistance of the thermistor is monitored by the
control system through simple voltage division, as shown on the right.
Garment and Circulation System
The team developed a scheme for body heat distribution based on communication
with medical professionals in the field; first priority was given to areas of the body in
which heat exchange is most effective. Based upon a thermal map of the human body,
especial emphasis was placed on tubing at the shoulders, neck, and back of the garment.
Using an artist’s mannequin as a guide, the team carefully designed a tube path that
would maximize heat exchange while avoiding pinch and strain points on the user’s
body. The original garment selected was a white synthetic longsleeved pullover athletic
shirt. However, the garment fell short in several ways. In tests, the pullover experienced
severed strain and stretching as it was donned, precluding the notion of a stable, strainfree network of tubing.
A looser fit was deemed necessary, and to address insulation issues, an interior
lining was added. The new design had the added benefits of increasing robustness and
make the tubes easier to attach without being visually obtrusive. We settled on a zippered
Spartan microfleece with a loose fit. The insulation compensates for the loose fit: the
tubes are no longer close to the skin on the entire tube length, so the system must regulate
the temperature of the air next to the skin instead. However, the most effective points of
heat transfer remain close to the skin, particularly those on the shoulders and the back of
the neck. The microfleece is thin enough to be worn under a heavy coat in the winter, but
light enough to be worn in the summer as well. A tailor’s pattern below shows the initial
visualization of the tube path through the garment.
Control System
The control system is what ties many of the key systems together. Its purpose is to
receive information about the current operation of the system from the sensors and in
response control the operation of the circulatory and thermoelectric systems. At the heart
of the control scheme is the microcontroller, a Cypress Programmable System on Chip
(PSoC). The PSoC is a customizable composite of analog and digital processing
capability with a customizable pin arrangement. The PSoC is programmed through a
comprehensive IDE and development board described in the Software and Tools section
of this report.
In designing the logical structure of the control system, the first aspect to consider
is the enumeration of inputs and outputs. According to the initial design assembled by the
team, the control system was meant to regulate the flow of power to the PETE by
adjusting a PWM output at the gate of a power MOS-FET. The PWM output should be
calculated from the sensory readings, raising or lowering the specific value of the PWM
duty cycle to raise or lower the effective voltage controlling the power MOS-FET. By
controlling the power to the thermoelectric, the temperature of the water is regulated. The
temperature sensor on the output of the heat exchange provides a feedback to the system
to adjust the level of power supplied.
As the design of the product developed, so did the control scheme for managing
it. After consultation with the customer, a manual override of the system was added,
shifting the focus from a purely automated system to one in which the user specified a
setpoint to the system which would be adjusted by the control system in response to
sensor input from inside the garment itself. In the final design, a five-position rotary
switch is used to allow the user to select one of five settings: Off, high cooling, low
cooling, low heat, and high heat. The switch position constitutes a digital input to the
PSoC, setting the system into particular modes of operation. The control flowchart is
shown in Appendix A.
The outputs of the PSoC must be monitored such that vital measurements (body
temperature, water temperature) all lie within hard limits. The hard limits are defined in
the table below.
Value
Limits
Water Temp. (°F)
50-120
Body Temp (°F)
70-99
Within this framework, the voltage to the PETE is varied to produce water
temperatures corresponding to particular setpoints, which in turn can be adjusted from
feedback from the body temperature thermistor. The initial setpoints for the PETE PWM
duty cycle are summarized in the table below.
Switch
Position
Duty Cycle %
High Cold
Low Cold
Off
Low Heat
High Heat
100
90
0
75
90
The disparity between the cold and heat initial setpoints is related to the efficiency
of the PETE. Since the PETE heats far more efficiently than it cools, the cooling
setpoints are uniformly larger.
Testing
Tests were performed to track the performance of the PETE in both heating and
cooling modes over time.
A graph of temperature change with respect to time for the cooling mode is shown
in the figure below. For the first trial, 1 liter of 120 °F water was cooled in an 80 °F air
temperature environment, meaning that there is actually a negative temperature
difference. The negative differential causes the system to operate at peak efficiency until
a water temperature of 80 °F is reached. At this point, a temperature difference started to
build up, reducing the cooling potential of the system. The temperature difference and
heat flow balance out at around 50 °F. At this point the amount of heat entering the
system through the air is equal to the amount that is being removed by the thermoelectric
system. If a larger temperature difference was required, than one could simply reduce the
amount of water in the system, meaning less heat would be absorbed by the atmosphere,
translating into less heat that needs to be removed to lower the water temperature. The
general trend can be seen from the figure by the rapid temperature change in the first ten
minutes, after which the temperature change converges to a limit in which the heat pump
cannot overcome the differential.
Cooling performance of a thermoelectric system. Time (x-axis) vs. Temperature change
(y-axis).
The heating performance of the system was tested in a second trial, as shown in
the figure below. This again shows temperature change with respect to time, except that
the initial temperature of the water was 50 °F. Initial heating performance is double that
of the cooling performance, since heating due to both the resistance of the device and the
thermoelectric effect is present. An interesting note is that in this mode, the heatsink is
actually pulling heat from the environment. The air outtake was measured to be 2 °F
colder than the air intake. The point at which the transition from both resistive and
thermoelectric heating to just resistive heating can clearly be seen in the figure below.
Heating performance of a thermoelectric system.
Summary
The goal of this project was to design and construct a temperature control system
as a wheelchair accessory to increase the comfort and independence of wheelchair-bound
poikilotherms. This goal has been accomplished. Our system is capable of cooling 1 liter
of water by 40°F in ten minutes or heating it by 40°F in half the time. It is stylish and
discreet, and it in no way impairs the mobility of the user. This prototype is built to last
and has been designed with considerable margin to ensure a long lifecycle. With that in
mind, we have intentionally designed this system for future development, creating a
simple and flexible platform for adding temperature readouts, refining diagnostics, and
customizing system variables to minimize noise and power consumption. The project has
been completed for a final prototype cost beneath the $500 allocated for the project as
tabulated below.
Final Budget
Part
Thermoelectric Module
Heatsink
Water Block
120mm Fans (2)
Water Pump
Thermal Greese
1/8 inch Tygon Tubing (30
ft)
Thermistors (3)
Relay
Quick Disconnects (2)
IGBT Transistors (4)
Inductor
Starter Jacket + Vest
Material
Microcontroller
Model Number
HP-199-1.40.8PR
TRUE 120 Black
XWB-1
DFS1238123000
WAL FRD-2-1
AS5-35G
R-3603
TH-10-44006
782-2C-24D
5012K38/44
STP300NH02L
PCV-2-104-10L
CY8C29466
Total
Cost
$45.20
$65.95
$34.99
$16.58
$67.65
$5.99
$11.70
$45
$5.50
$25.46
$25.20
$5.28
$75
$8
$437.50
Appendix 1: Individual Technical Contributions
Albert Alexander
Albert designed and built the control circuitry and was responsible for
system integration. The job of system integration led him to be closely
involved with every system in the entire product, and his contributions
ranged throughout them. He was in charge of electrical safety, designing
a grounding scheme, breaker placement, and circuit drivers to ensure safe
operation even in the case of malfunction. He built all electrical
interconnects and designed board routing for maximum reliability, and
worked with Steven Shane to design active diagnostics and choose
automatic shutoff conditions. Another primary focus was on power
circuitry, and in conjunction with Stephen Zajac he designed, tested and
built the low-amperage control circuit. Albert gathered the requirements
for each individual power setting, choosing MOS-FETS, managing
sinking. He also chose a relay as the best method of creating a doublethrow switch. He designed, tested and built the 24V/5V DC switcher and
designed and built the case.
Steven Shane
Steven Shane was in charge of selecting the microcrontroller technology
to build the control system. At first he selected the Microchip line of
PIC48f5255 microcontrollers to manage the analog inputs and generate
PWM output. However, as the project developed he had to choose a new
architecture due to increased demands upon the control system, and
selected the a Cypress PSoC for greater controlling power.Additionally,
he worked closely with Albert and Melissa to determine the number and
nature of inputs and outputs to the control system.
The control aspect of the project was contributed by Steven, as he
designed, programmed, implemented simulated and tested the control
system, running through a series of logical architectures. The design
changed throughout the lifetime of the project based upon shifting
requirements placed on the system by other portions of the project.
According to these needs and the limitations of the sensory inputs, Steven
designed the control system for use on the PSoC to be a set-point based
feedback system with variable setpoints based upon temperature sensor
data. He designed and implemented a series of diagnostics and procedural
safeguards which preclude the system operating in an unsafe mode. The
algorithm is designed such that if unreasonable or unsafe temperatures
are detected at the water flow the entire system shuts down rather than
continue circulating water of unknown provenance.
The final flowchart for the design system can be seen in Appendix 3 of
this report.
Melissa Stroud
Melissa Stroud focused her efforts on concerns related to the temperature
sensors as well as the mechanics of the garment and the tubes inside.
After gathering information on the requirements for the sensors
(temperature range, sensitivity, hardiness, power requirements) she
selected a specific class of thermistors and built the circuit linking them
to the control system. She performed additional coarse testing to verify
the operation of the thermistors at different temperature extremes.
Melissa also spearheaded the garment section of the project. She built the
first prototype shirt and experimented with the optimal way to attach the
water-carrying tubes to the garment securely and without strain. Melissa
devoted significant effort towards choosing the specific path on the
garment that the tubes would follow to maximize effective heat transfer.
The path was also designed to avoid portions of the body that would
pinch the tubes or put stress on them. Similarly, the tube path was chosen
such that the tubing formed zero closed loops, eliminating the possibility
of constriction. She oversaw the final placement of tubes in the interior
vest lining of the jacket, as well as securing the tubes inside the garment
via cloth sleeves.
Stephen Zajac
Stephen Zajac’s main responsibility was creating the heat exchanger
system to be used in the final product. This involved selecting the
thermoelectric device to be used, and choosing a compatible a heatsink,
water block, fans, and water pumping system. In order for the
thermoelectric device to work as it is advertised to, the supporting
components must have the correct specifications. Another responsibility
was to make a working design for the DC-DC converter used to power
the thermoelectric module. This device requires a specific voltage and
current to operate at peak efficiency, making control and accuracy of the
converter a significant issue. The TE module also can draw up to 9 amps
when in operation, making high current design issue important.
Appendix 2: Technical Resources
Omega Engineering Inc.
Cypress Semiconductor
Microchip Microcontrollers
Cypress Design forums
Analog - DAC With Analog Modulator AN2199
Heat Sink/ Water Block Information
Dr. G. Wierzba: ECE301/302 Notes
www.omega.com
www.cypress.com
www.microchip.com
http://www.cypress.com/forums
http://www.cypress.com/?rID=2783
http://www.crazypc.com/products/trueblack-50984.html
www.egr.msu.edu/~Wierzba
Appendix 3: Control Flowchart
IN
START
TYPICAL
FALSE
FALSE
SWITCHVAL != 4
||
SINKTEMP > MAXSINKTEMP
TRUE
FANPWM=0;
PMPPWM=0;
TEMPWM=0;
VHEAT=0;
GOTO START
FANPWM = 100;
PMPPWM = 100;
WAIT 2 SECONDS;
VHEAT = 1;
SWITCHVAL < 4
VHEAT = 0;
WATERTEMP <
H2OSETPOINT+H2OTOL
WATERTEMP >
H2OSETPOINT-H2OTOL
(WATERTEMP >
H2OSETPOINT-H2OTOL)
WATERTEMP <
H2OSETPOINT+H2OTOL
TEMPWM = 0;
TEMPWM >= 5
TEMPWM <=
95
TEMPWM -= 5;
TEMPWM += 5;
WAIT 2
SECONDS
TEMPWM = 100;
BODYTEMP >
LOWER_REASONABLE
&&
BODYTEMP <
UPPER_REASONABLE
BODYTEMP
BODY_SETPOINT
SWITCHVAL < 4
BODYTEMP <
BODYSETPOINT+BODYTOL
BODYTEMP >
BODYSETPOINT-BODYTOL
BODYTEMP >
BODYSETPOINT-BODYTOL
BODYTEMP <
BODYSETPOINT+BODYTOL
H2OSETPOINT =
MINH2O;
H2OSETPOINT
>= MINH2O+5
H2OSETPOINT
<= MAXH2O-5
H2OSETPOINT
-= 5;
H2OSETPOINT
+= 5;
WAIT
GOTO START
H2OSETPOINT =
MAXH2O;
5-pin Rotary
Switch
5V DC, Low Current
Analog
Thermistor Input
PSoC
PWM Variable Duty Cycle
Digital 5V
PWM Variable Duty Cycle
24/5V buck
converter
Dual-Pin
Dual-Throw Relay
Power MOS-FET
Thermoelectric
24 V battery
Power MOS-FET
Electric Fan
Pump
Figure 1: Data Flow
Thermoelectric Module
Product Price
Imax
(amps)
HP$43.90 11.3
1991.4-0.8
Qmax
(watts)
172
Vmax
(volts)
DTmax
A
(Th=300K) (mm)
67
40
B
(mm)
40
H
(mm)
3.2
24.6
Source: http://www.tetech.com/Peltier-Thermoelectric-Cooler-Modules/High-Performance.html
Water Pump
Part#
159729
Fans
Brand
Scythe
Mfr#
FRD-2-1
Model
Shut-Off Pres.
2.5 Psi
Fan Size
DFS123812- 120mm
3000
Current (amps)
1.5
RPM
Air Flow
3000
±10%
RPM
133.60
CFM
Noise
Level
45.90
dBA
Voltage
12v
Dimensions
120 x 120 x
38mm
Heatsink
Brand
Thermalright
Model
True 120
Dimensions
L63.44 x W132
x H160.5 mm
Water Block
Part#
Dimensions
Weight
XWB-1
L64 x W48 x H17mm
250g
Weight
790g
Heat Pipes
Six heat pipes
with black
nickel plated
Material
Copper
Source: http://www.clunk.org.uk/martins-liquid-lab-articles/thermalright-xwb-01-water-block-flow-rate-testing.html