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Electrocardiograph Demonstration Board
Design Team 6
Fall 2012
Matt Affeldt Derek Browers Phil Jaworski Jung-Chun Lu Alex Volinski
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Executive Summary
Design Team Six’s Electrocardiograph (ECG) Board was designed as a
demonstration board to replace Texas Instruments' (TI) current demonstration board.
Their current board uses outdated chips and antiquated printed circuit board (PCB)
design; the objective was to create an updated demonstration board concurrently
displaying contemporary TI chips and modern PCB design. The design created by the
team accomplished the goals of making a modern demonstration board for TI to use.
The simulated results matched what should be expected when using an ECG Board
and maintained those results consistently. After creation of the actual ECG
demonstration board, the lab results matched those of the simulations ran on the
design, and were what was desired. The final product is now a fully functional ECG
demonstration board for TI to use as a demonstration for the recent peaked customer
interest in ECG boards.
Acknowledgements
Design Team Six would like to thank the following persons for their help in the design of
this project.
The Texas Instruments sponsor, Mr. Peter Semig : For providing references on PCB
design, electrocardiography, and ECG circuit design. Also, for helping hone our final
PCB designs.
The team facilitator, Professor Samuel Ratnajeevan H. Hoole : For his direction
throughout the semester on our technical progress, as well as his hard work editing our
documents and commenting on presentations.
The class Teaching Assisstant, Steve Zajac : For his assistance in troubleshooting
functionality issues arising from the use of the INA333. Also, for assistance in the
testing of our stability boards.
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Table of Contents Executive Summary ................................................................................................................................. 2
Acknowledgements ................................................................................................................................. 2
Chapter 1 – Problem Background ....................................................................................................... 5
Chapter 2 – Exploring the solution space and selecting a specific approach ................................. 8
2.1 – Solution Exploration ................................................................................................................ 8
2.2 – Fast Diagram ........................................................................................................................... 9
2.3 – Critical Customer Requirements .......................................................................................... 10
2.4 – Chosen Design Solution ....................................................................................................... 13
2.5 – Budget .................................................................................................................................... 13
2.6 – Gantt Chart ............................................................................................................................ 16
Chapter 3 – Technical Achievements and Progress ....................................................................... 19
3.1 – Software Used ....................................................................................................................... 19
3.1.1 TINA-TI ............................................................................................................................... 19
3.1.2 – PCB ARTIST ................................................................................................................... 19
3.2 – Overview of Technical Assignment...................................................................................... 20
3.3 – Creating the Stability Boards ................................................................................................ 21
3.3.1 – Edited and ran Error Rule Check (ERC) on the TINA-TI schematics Mr. Semig Provided ....................................................................................................................................... 21
3.3.2 – Simulated the schematics in TINA-TI ........................................................................... 22
3.3.3 – Created the layouts for the two stability boards in PCB Artist .................................... 22
3.3.4 – Fabricated the PCB Boards and ordered components ............................................... 23
3.3.5 – Populated and tested the boards .................................................................................. 24
3.3.6 – Problems obtaining exact percent overshoot numbers for Mr. Semig ....................... 24
3.4 – Electrocardiograph Design ................................................................................................... 24
3.4.1 – Designed the ECG schematic ....................................................................................... 24
3.4.2 – Simulated the finalized schematic ................................................................................ 25
3.4.3 – Designed the ECG layout in PCB Artist and Eagle ..................................................... 26
3.4.4 – Populated and tested the two ECG Boards ................................................................. 27
Chapter 4 – Final Testing and Proof of Functionality ...................................................................... 30
4.1 – Testing Goals ......................................................................................................................... 30
4.2 – Testing Set Up ....................................................................................................................... 30
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4.3 – Verification of Amplification .................................................................................................. 31
4.4 – Verification of Filtering .......................................................................................................... 33
4.5 – Verification of Power Regulation .......................................................................................... 34
.............................................................................................................................................................. 35
Chapter 5 – Summary and Conclusions ........................................................................................... 35
5.1 Budget and Cost ....................................................................................................................... 35
5.2 Schedule ................................................................................................................................... 36
5.3 Executive Summary ................................................................................................................. 37
5.4 Conclusions and suggestions for future work ........................................................................ 37
Appendix I: Technical Contributions ................................................................................................. 39
Matt Affeldt ...................................................................................................................................... 39
Derek Brower .................................................................................................................................. 40
Phil Jaworski ................................................................................................................................... 42
Jung-Chun Lu .................................................................................................................................. 43
Alex Volinski .................................................................................................................................... 45
Appendix II: References ..................................................................................................................... 47
Appendix III: Technical Attachments ................................................................................................. 49
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Chapter 1 – Problem Background
Electrocardiography (ECG) is the use of electrical signals, detected by electrodes
attached to the surface of the skin, to interpret the electrical activity of the heart over
time. The knowledge acquired from the electrical response of the heart is used in
medical and research facilities worldwide to provide a greater understanding of heart
activity and treat ailing patients. The electrodes used to measure the voltages are
connected to an electrocardiograph machine; this machine contains a circuit that
detects and amplifies the charges created on the skin by a beating heart before
recording and outputting the results for observation.
Texas Instruments (TI) currently has an outdated ECG demonstration board built
to drive consumer interest in using their products for ECG machine solutions. Over the
last few years, client interest and consumption of ECG products has seen a noticeable
growth spike, yet Texas Instruments does not have a contemporary example of their
chips and designs being applied to ECG solutions. The Electrocardiograph project
tasked to Design Team Six aims to fill the void of a modern ECG demonstration board
for TI. If designed well, this resulting ECG board will be used to help enhance customer
interest in Texas Instruments’ products for their ECG designs.
The current ECG demonstration board uses chips that are a decade old and was
fabricated using antiquated PCB layout techniques. This means the current board lacks
the precision and noise cancellation that current technology and proper design can
provide. In order to fabricate a modern ECG printed circuit board, entirely new chips and
components will need to be selected to populate the PCB. This will also require an
entirely new circuit capable of performing the same readings as the old ECG board with
more precise results. Precise measurements and minimal noise are very important
components of ECG design due to the small signals ECG boards are designed to
measure.
The signals produced by the heart and recorded by the electrodes are minute in
nature and the recording requires precise instrumentation capable of exceptional noise
cancellation. A typical heartbeat recording on an ECG consists of three waves and a
complex. The complex, illustrated in figure 1 as the signal defined by the points QRS,
creates the electrical signal with the largest amplitude during a heartbeat. This QRS
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complex has typical amplitudes of under 5 millivolts and durations of 80 to 120 ms. The
T wave displayed in figure 1 has the longest duration, which is 160 ms. These numbers
illustrate why precise instrumentation and maximum noise cancellation are needed to
record interpretable ECG signals.
Figure 1: ECG recording of a typical heartbeat
There are some clear objectives that need to be met when creating the new ECG
design. The most well-defined objective is all op-amps, instrumentation amplifiers, and
power converter chips must be precise, modern Texas Instruments chips. The
components used to create the rest of the circuit must be precise and use surface
mount packaging, which only occupies the surface layer of a PCB, to create more
flexible PCB layout design. The entire design of the circuit and PCB layout needs to be
as robust as possible. This is where the most engineering expertise is needed.
The created design of the circuit and layout is new and not based off the old
demonstration board. The only similarity is both boards are 3-lead ECG boards, which
means three electrodes provide the signals read by our ECG board. The new circuit can
be broken into four parts shown in Figure 2. These are the INA front end or input, the
INA output, the right leg drive, and power. The acronym INA represents the INA333,
which is a very low power instrumentation amplifier with impressive precision. This chip
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will be used to combine signals from the three leads into a single clean output signal
displaying the activity of the heart.
Figure 2: The INA 333
Vin- and Vin+ create the INA front end (input)
RG is replaced by the right leg drive circuitry
Vout is the INA output
V+ and V- are the connections to power
The input on the INA front end comes from the right and left electrodes. The new
design includes current limiting resistors, resistor and capacitor (RC) filtering, and RC
common mode voltage. This design helps minimize noise from voltage, noise from
current, and power consumption. These are all very important features to ECG design.
The Right leg drive is used to provide a common mode bias and noise cancellation for
the circuit. This portion of the circuit will contain a buffer and an RC compensated
amplifier to increase overall circuit stability. The power portion of the circuit is designed
to accept voltages from 7-10V, the board will be powered with a 9V battery, and
produce exactly 5V with 100 mA current. This allows for precise control of the power to
the chips in the circuit. Finally, the INA output will contain a buffer and the option of
using a passive or active filter on the output. This choice of filtering allows for optimal
output for reading electrical activity. These circuit design choices incorporate solutions
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to many of the ECG problems faced when building an ECG board, and they allow for
confidence in a successful design.
The printed circuit board layout contains the actual routing between components
and the mounts to attach all our components to. There are many trade-offs that must be
considered when transferring a circuit to a layout. Modern design choices incorporated
into the layout include cutting out the ground plane under the inverting nodes of our
chips and close placement of op-amps and the INA to the input signals they manipulate.
Cutting out the ground plane beneath inverting nodes increases impedance in the
ground plane; however, it prevents current flowing through the ground plane from
affecting the inverting nodes. Since these are a sensitive area on our circuit, it is worth
cutting notches out of the ground plane and increasing the impedance. Choosing this
trade-off will increase the circuit’s precision and decrease noise. Placing chips as close
to their input signals as possible greatly decreases the opportunity for interference in the
signals. Both these layout decisions help modernize the ECG layout compared to the
old demonstration board.
Incorporating all these new designs into a modern fabricated ECG board will
provide Texas Instruments with an up-to-date board featuring their chips as cutting edge
ECG solutions. The final board will provide a tangible marketing and demonstration tool
they can point to as a reference when clients have questions or problems with their
designs. The design of the board should successfully fulfill this agenda due to the
extensive electrical issues considered. The solutions to these are reflected in the design
of the circuit and the printed circuit board layout.
Chapter 2 – Exploring the solution space and select ing a specific approach
2.1 – Solution Exploration
During the initial planning phase of any large, team-oriented design project there
are numerous strategies the group can employ to develop a functional solution. As a
result of this flexibility, customer requirements and technical constraints must be taken
into account and weighted in order of importance. Evaluating the importance of each
requirement and constraint narrows the number of possible solutions; this allows for
creation of a final solution designed to maximally benefit the customer it was designed
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for. Using techniques practiced by Six Sigma experts in industry, including a fast
diagram and the house of quality, a practical strategy can be developed to produce this
solution.
2.2 – Fast Diagram
Six Sigma is a systematic data driven approach to problem solving intended to
meet customer needs while improving quality, reliability, and manufacturability of a
product. A very beneficial tool used in Six Sigma design is the FAST diagram. The
diagram is a flow chart constructed from left to right. The left side of the chart lists the
primary task to be performed followed to the right by the main functions. Subsequent
secondary functions needed to complete the main functions are listed to the right of the
main function. Tracing the diagram from left-to-right will answer the question how each
proceeding objective will be accomplished. For example, the main functions answer
how the primary task will be accomplished. The reverse direction, right-to-left, will
answer why each function is performed. Asking why a main function is performed, for
example, can be answered by tracing the diagram to the right and reading the primary
task. Applying a FAST diagram to a new project allows a relevant solution flow to
become apparent and minimizes peripheral objectives that are generally unnecessary to
the design. Figure 3 below shows the FAST diagram developed to assist in the design
of the ECG demonstration board.
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Figure 3: ECG FAST Diagram
2.3 – Critical Customer Requirements
After completing the FAST diagram, the Team had to meet with Texas
Instruments in order to identify other critical considerations that had to be implemented
in the design process. Texas Instruments believed the most important considerations
were accuracy, low noise in the output, and an optimal design for functionality. Some
other minor considerations brought up were meeting cost requirements, using TI
Components, and interfacing with other hardware and external components. The board
can potentially be used in life-threatening emergencies, so the clarity of the output
signal will be essential. From these requests, a Six Sigma chart called a House of
Quality Matrix was created. This diagram, shown below in Figure 4, represents the
correlation of certain desires of the customer, capabilities of the device in question, and
possible solutions to the project. Similar ECG devices found online were analyzed as
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competitors, and their statistics had gone into consideration in order to evaluate the
differences between the different boards. The horizontal part of the diagram is each of
the customer’s requirements ranked with values of importance, the vertical axis shows
each functionality requirement of the board, and the diagram on the right gives a
representation of how Team 6’s design compares with that of the other companies.
From this matrix, it was easy to determine what the strengths and weaknesses of the
design were.
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Figure 4: House of Quality
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2.4 – Chosen Design Solution
After several interactions with Mr. Semig, a design that the team and the sponsor
agreed was ideal underwent implementation. The main goal was the ideal functionality
of the board, focusing less on other issues such as cost or ease of manufacturing. In
the final design, an RL Drive Amplifier serves for noise cancellation and as common
mode bias. It reduces common-mode interference and increases stability of the circuit.
It provides a common electrode bias at the reference voltage, and feeds back the
inverter common-mode noise signal to reduce the overall noise seen at the inputs of the
instrumentation amplifier’s gain stage. The TI INA333 low power amplifier was used as
the main I/O amp for the design and multiple OPA2333 amplifiers that act as filters at
different points in the circuit. To step down the 9 volt battery to the voltage required by
the IC’s, the TI TPS5410 converter was used because of its low noise capabilities and
high efficiency. The input set up consists of PCB pads connected to both arms and the
right leg of the patient, and the parallel RC combination connected to each input
represents the added passive-electrode connection impedances. All these components
were used to reduce the overall noise signal at each input, which filters the residual
noise, or reject common-mode noise, essentially creating the clearest possible output
signal. The final design uses a 2-layer PCB board for simplicity and cost efficiency, and
top level components with optimal design for functionality and accuracy.
2.5 – Budget
Team 6 had a budget of $500, and the goal was to achieve the lowest possible
cost for the project while still meeting the requirements of the sponsor. Fortunately, TI
provided the expensive components, such as the ECG simulator, CARDIOSM 2, and
the Stellaris Evaluation Kit. Since TI provided these units, only the actual ECG PCB
design and construction needed to be funded. TI also supplied all of the microchips
through their free sample program on the Texas Instruments Website, and the final
design used a fairly inexpensive two layer board in order to use multiple ground points.
As shown in table 1 on page 14, the cost to recreate one of these boards is $45.51
assuming the amplifiers can be acquired for free through the TI website. The cost for
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replicating this board does not include the shipping fees that were incurred or the fact
that enough resources were purchased to create a total of four ECG boards,
Team 6 had a budget of $500, and we aimed to achieve the lowest possible cost
of the project while still meeting the requirements of our sponsor. Fortunately for us, TI
provided the expensive components, such as the ECG simulator, CARDIOSM 2, and
the Stellaris Evaluation Kit. Since TI provides us with these units, we only needed to
fund the actual ECG PCB design and construction. TI also supplied us with all of our
microchips through their free sample program on the Texas Instruments Website, and
our final design used a fairly inexpensive two layer board in order to use multiple ground
points. Shown table 1, the cost to recreate one of these boards is $45.51 assuming the
amplifiers can be acquired for free on the TI website. The cost for replicating this board
does not include the shipping fees we incurred or the fact that we wanted to have
enough resources to create a total of four ECG boards, but our team total is shown
below, falling well below the $500 budget we were initially given.
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Table 1: Diagram of Costs
Part Quantity Cost/Unit Cost 2-Layer PCB Fabricated
Board 1 $33.00 $33.00 1 Schottky Diode 60V/1A 1 $0.540 $0.54
3.24K Resistor 1% 1 $0.060 $0.06 10K Resistor 1% 1 $0.020 $0.02 330K Resistor 1% 2 $0.100 $0.20 62K Resistor 5% 4 $0.050 $0.20 10K Resistor 5% 4 $0.050 $0.20 100K Resistor 5% 1 $0.050 $0.05 10M Resistor 5% 1 $0.050 $0.05 1M Resistor 5% 2 $0.050 $0.10
150K Resistor 5% 1 $0.050 $0.05 Ground Test Points 7 $0.334 $2.34
Power/Signal Test Points 7 $0.334 $2.34 330uH Power Shield Inductor 1 $2.030 $2.03
5600pf Ceramic Cap 50V 1 $0.280 $0.28 10 uf Ceramic Cap 16V 1 $0.250 $0.25 1 uF Ceramic Cap 16V 1 $0.160 $0.16
1000pf Ceramic Cap 50V 2 $0.130 $0.26 820pf Ceramic Cap 50V 1 $0.190 $0.19 10pf Ceramic Cap 100V 1 $0.300 $0.30 0.1uf Ceramic Cap 50V 5 $0.100 $0.50 330pf Ceramic Cap 50V 1 $0.140 $0.14 33pf Ceramic Cap 100V 4 $0.246 $0.98 100uf 10V tantalum Cap 1 $1.270 $1.27
TPS5410 Chip 1 $0.000 $0.00 OPA2333 Chip 4 $0.000 $0.00 INA333 Chip 1 $0.000 $0.00
Total Spent for 1 ECG $45.51
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2.6 – Gantt Chart
The Gantt chart is a tool that the team utilized in order to keep track of all
progress being made and was used as a schedule that prevented the team from falling
behind. The project was divided into subsections that provided a time estimate for each
step of the project. With this chart, it was easy to visualize the critical path of events
that needed to be completed in order to achieve all goals, and be able to stay within the
time limits throughout the semester. Figure 5 shows the Gantt chart for Design Team 6.
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Figure 5: Gantt Chart
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Figure 5 continued: Gantt Chart Timeline
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Chapter 3 – Technical Achievements and Progress
3.1 – Software Used
The technical work associated with designed an ECG board involves the creation
of schematics and layouts for circuits. TINA-TI will be used to design schematics and
run simulations. The schematics are then transferred to PCB Artist where the layout will
be created to match the schematic.
3.1.1 TINA-TI
Learning how to create and simulate schematics in TINA-TI is very important
because simulations allow for assurance the designed prototype functions correctly.
PCB Artist allows for schematic and layout creation, but users are unable to simulate
their circuits to ensure proper performance. Due to the high cost and long turn-around
times associated with fabricating PCBs, proven performance through simulation is
necessary to save time and money.
Texas Instruments provides downloadable TINA-TI library files for a high
percentage of their chips. These can be added to TINA-TI libraries for chips that aren’t
present in the default libraries. Having access to these files created by TI specifically for
simulations allows for a high degree of accuracy and reliability in simulation results. This
feature is why TINA-TI was used to run simulations on the ECG demonstration board.
3.1.2 – PCB ARTIST
PCB Artist is a software tool used to create layouts for printed circuit boards.
Development of a layout is broken into two parts, the schematic and the layout.
Schematic creation is important because the schematic can be linked to the layout. This
will show the user where connections must be made in the layout based on the
schematic. For a schematic to accurately match the simulations performed in TINA-TI,
the schematic created in PCB Artist must be identical. After the schematic matches the
simulated TINA-TI circuit, it can be transferred to the layout.
The layout of a PCB defines where copper will be added to the non-conductive
substrate that comprises most of the board. The copper will create mounts where
components can be attached as well as electrically conductive traces which create
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connections between components. Most layout software, including PCB Artist, is
essentially a Computer-Aided Design, CAD, tool used to draw where each footprint and
trace must be placed. Footprints on the board must match the footprints on the selected
components to ensure optimal soldering connections are made when the final board is
assembled. Since constructing a layout isn’t as intuitive to an engineer as a schematic,
PCB Artist allows the schematic and layout to be linked. This allows the engineer to
check if the layout matches the schematic.
PCB Artist was chosen above other layout design software due to the intuitive
User Interface, the ability to order boards directly from Advanced Circuits without having
to generate output files and for the discount offered by Advanced Circuits to students.
Utilizing the student discount allowed the $500 budget to be easily met with excess
funds to spare.
3.2 – Overview of Technical Assignment
Mr. Pete Semig, the design team sponsor from Texas Instruments, developed
two stability circuits requiring minor modifications that TI intends to use for future
applications. These schematics needed to be slightly modified, simulated, and a layout
needed to be created for each. The purpose of making these boards was to introduce
schematic design and simulation, layout design, the fabrication process, populating
PCB boards and testing final PCB designs. Stability is also very important to ECG
circuits, especially in the right leg drive portion. Both circuits were designed with
switches which, depending on whether they were open or closed, put the boards in a
stable or unstable state.
Following the design of the stability boards, the ECG board was designed. This
required creating, from scratch, a schematic to eventually fabricate. The schematic was
developing utilizing web research, engineer to engineer forums, input from our sponsor,
and technical documents provided by our sponsor on layout design and ECG. Once
developed, the schematic went through revisions before being simulated. The layout
was created once simulations in TINA-TI matched desired functionality. This went
through a couple revisions before the board was fabricated, populated and tested.
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3.3 – Creating the Stability Boards
3.3.1 – Edited and ran Error Rule Check (ERC) on th e TINA-TI schematics Mr.
Semig Provided
As mentioned in the technical overview, the basic schematics were provided by
Mr. Semig. Minor modifications were made to stability circuit 1, shown below in Figure
6, including removing the series capacitor from the design, increasing the value of the
voltage divider resistors, and changing the op amp to the OPA 365. The OPA 365 was
not in the TINA-TI library, so a macro was downloaded to TINA-TI from Texas
Instrument’s website. TI has macros for almost every part they make on their website
which define the part for TINA-TI simulations. For stability circuit 2, shown on the next
page in Figure 7, the value of the load resistor was changed to 10 kΩ. The electrical rule
check (ERC) was run to ensure the schematics had no errors in wiring after each
change. Simulations were ran to ensure proper performance, and then the schematic
was transferred to PCB Artist in preparation for layout creation.
Figure 6: Stability Circuit One
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Figure 7: Stability Circuit 2
3.3.2 – Simulated the schematics in TINA-TI
Transient simulations were run on the TINA-TI schematics with a one volt step
input to discover what the response of each circuit was under stable and unstable
conditions. These simulations can be performed within TINA-TI by defining the input
and running a transient analysis on the output. This provides a graph of the response of
the circuit. The switches can be opened or closed before analysis simply by clicking on
them within the circuit. Simulation results from the analyses were saved to compare to
the lab test results on the boards. Simulation results for each board are attached in the
technical appendix next to the corresponding schematic and layout.
3.3.3 – Created the layouts for the two stability b oards in PCB Artist
The layouts were created based on the updated simulated schematics in TINA-
TI. Some components from the schematics were in the PCB Artist library already, but
libraries were created for the banana jack, test point, and op amp. Mr. Semig imparted
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the parameters for the banana jack and test points in a weekly teleconference, and the
parameters for the op amp were obtained from its datasheet on TI’s website. In order to
make a new component to use in PCB Artist, a schematic and PCB symbol for each
part was created in the library manager. Both symbols needed to be made so the part
could be placed in the schematic and the ‘Schematic PCB’ tool could be ran. The
‘Schematic PCB’ tool allows the schematic to be transferred to the layout with the
click of a button. This also allows the two views to be linked which shows where
connections should be made based on the schematic wiring.
After creating all components not already included in the PCB Artist library,
layouts for both circuits were produced following a few design parameters. The layouts
were designed to flow from left to right, per Pete, with Vin on the left side of the PCB and
Vout on the right. The banana jacks for power and ground were placed at the top of the
boards with the decoupling capacitors directly below them. Signal traces were specified
to have a width of 15 mils and the power and ground traces a width of 25 mils. The rest
of the components and traces were arranged around these parameters with a design
intended to minimize overall board area and the length of traces between components.
After creating the layouts, Design Rules Check (DRC) was run to make sure the layouts
passed all design rules necessary for functional fabrication. The layouts for both stability
boards are attached in the technical appendix beneath their corresponding schematic.
3.3.4 – Fabricated the PCB Boards and ordered compo nents
Boards can be ordered directly through the PCB Artist software with a discount
for students. Under Settings>PCB Configuration a user can specify they want to order a
student 2-layer basic board, the turnaround time for fabrication and the number of
boards desired. Then, it is as simple as clicking the order now button on the menu bar,
entering any promotional codes for discounts, registering and providing a school
address to ship the boards to and finally paying. A five business day fabrication time
was chosen to maximize the student discount and the boards arrived just over week
later. During this time, the component orders were placed so population of the boards
could be completed immediately after arrival.
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3.3.5 – Populated and tested the boards
Once all our parts and the PCB boards had arrived, the boards were populated
and the response was tested using a function generator, power supply and
oscilloscope. Initially, a great deal of noise and oscillation was present within the
boards, but, after adjusting the oscilloscope and briefly placing a 100 pF capacitor
between Vin and ground to remove oscillations, the oscillation and most of the noise
caused by interference was eliminated. To provide a clearer picture averaging was
enabled. This smoothed the minimal remaining noise. The lab test results closely
matched simulation results. This confirmed the fabricated circuits were functioning
properly. The percent overshoot in the lab was within 5% of the percent overshoot
calculated by the simulations. This held true for both circuits. A PowerPoint presentation
of the test results and simulation results was prepared for Mr. Semig. The lab test
results are displayed below simulation results for the corresponding board in the
technical appendix.
3.3.6 – Problems obtaining exact percent overshoot numbers for Mr. Semig
Originally, Mr. Semig wanted a comparison of the percent overshoot in
simulations to the percent overshoot in lab results. The ordered test points had not
arrived, and the lab results were obtained by improvising and wrapping a wire through
the points where inputs, grounds, and test points would be. This allowed a response to
be obtained with averaging enabled, but did not allow very accurate overshoot numbers
to be captured. The test points arrived later, but Mr. Semig wanted the ECG board to be
prioritized.
3.4 – Electrocardiograph Design
3.4.1 – Designed the ECG schematic
The ECG schematic was built from scratch based on PowerPoint slides provided
by Mr. Semig, conducted research and feedback from Mr. Semig after each draft. The
original schematic was created in TINA-T. This schematic was used for simulations to
guarantee proper functionality before being transferred to PCB Artist, which is used to
create a layout that matches the simulated schematic.
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The circuit was built using the INA333, TPS5410 and OPA2333. These chips
were available as free samples from Texas Instruments (TI). The INA333 is the
instrumentation amplifier that was designed for portable medical applications. This
amplifier accepts the inputs from the right and left arm while providing a right leg drive
and output signal. The OPA2333 op-amps were used in the right leg drive output
circuitry to create buffers and active filters. Finally, the TPS5410 was utilized to create a
clean 5 Volt low-dropout (LDO) power supply from a 9 Volt battery.
The ECG schematic went through three revisions before being simulated and
transferred into a layout. These revisions included changing the power chip from the
TPS5430 to the TPS 5410. This was done because the TPS5410 was easier to solder,
provided greater efficiency, and allowed better control of the current output to the rest of
the circuit. The output of the INA333 was modified to include a passive resistive and
capacitive filter, RC filter, as well as an active filter utilizing the OPA2333. Jumpers were
included to allow filter selection. Resistors and capacitors were also added to the
OPA2333 amplifier in the right leg drive circuitry to increase stability throughout the
entire circuit. The last revision was included on the INA front-end. This affects the input
right and left arm signals. Current into the INA333 was limited and the common mode
voltage was better established through revising the RC filters on the INA333 front –end.
3.4.2 – Simulated the finalized schematic
In order to create working ECG demonstration board without having to place
multiple revised orders, numerous simulations were ran on the TINA-TI schematic to
determine functionality of the prototype. Unfortunately, the power chip selected, the
TPS5410, did not have any macros available online or in the TINA-TI libraries.
However, a working schematic using the TPS5410 was verified using Texas
Instruments online WebBench tool. This tool provides simple power designs, among
others, that meet specifications input by the user. A few simulation results from TINA-TI
are attached in the technical appendix of the report below the TINA-TI schematic. These
match the expected functionality of a three lead ECG board.
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3.4.3 – Designed the ECG layout in PCB Artist and E agle
The ECG schematic was transferred from TINA-TI, post-simulations, to PCB
Artist to create the layout. A rough draft version was prepared for Mr. Semig who noted
a few necessary changes. He also said the initial version was ready for fabrication once
the changes were made.
Mr. Semig told us to check the total current our LDO power supply needed to
supply to the op-amps (OPA2333) and instrumentation amplifier (INA333), and try to
increase efficiency. We had to filters at the output to select between. One filter was
active; the other was passive. However, we didn’t place jumpers at each end of the
filter, so we added additional jumpers. This afforded us the ability to isolate the filter we
weren’t using. He also wanted op-amps moved closer to the source of their signals. This
helps to decrease possible interference to the signal. Finally, he suggested adding the
battery directly onto the board and cutting the ground plane out beneath the chips
inverting nodes. The inverting nodes were particularly sensitive areas of our circuit.
Removing the ground plane beneath these nodes added impedance to the ground
plane, but did not allow current flowing through the plane to affect the inverting nodes.
The cut out ground plane is displayed below in Figure 8 on the unpopulated board. The
figure shows the top layer view of the board. The ground plane is on the bottom layer.
The light green areas where the light is shining through show where the ground plane
was cut out.
Figure 8: The light green areas highlight the ground plane cut-outs
27
These changes may sound extensive and severe, but they were mostly minor
adjustments made on the layout. After all changes had been made, the layout was
ordered. The finished layout is attached in the technical appendix of this document.
Immediately after ordering the boards, the extensive part order was created, double
checked and ordered. Additional INA333 and OPA2333 chips were ordered. This was
done because they were free and would guarantee we had access to as many
functional chips as necessary for testing.
Due to the extensive turnaround time associated with ordering a board through
PCB Artist, an additional layout was created in Eagle. Eagle allows Gerber files to be
generated, which can be used by the ECE shop to create a simple PCB board. The
shop board wasn’t used for the final design because it doesn’t have access to tools
required to create as precise or high-quality of boards as Advanced Circuits. This board
was created simply for testing and to guarantee a populated board was ready for
Design Day. Fabricating a board through the ECE shop proved invaluable because,
even though the Advanced Circuits order was placed nearly three full weeks before
Design Day, the final Advanced Circuits PCB did not arrive until Tuesday, December
4th. This made meeting the deadline for creating a working ECG PCB in time for
inclusion in the final report and presentation the most difficult deadline to meet for the
project.
3.4.4 – Populated and tested the two ECG Boards
The ECE shop board was done a week before the Advanced Circuits board
arrived. Population proved to be difficult due to the small scale components and chips
used. The team also discovered the wrong INA333 footprint had been used, so a
SurfBoard has to be used. Figure 9 below shows the scale of the INA333 chip on the
SurfBoard compared to a quarter and ECE lab soldering iron tip. Due to the small scale
of the board, multiple shorts were created during population. Multiple hours were spent
testing the board to find the any shorts in the circuit, but the team was unable to create
a correctly functioning ECG from the ECE shop boards. The final ECE shop board is
shown in Figure 10 below Figure 9.
28
Figure 9: INA333 compared to the soldering iron tip
Figure 10: ECE Shop Board design in Eagle
29
When the Advanced Circuits board finally arrived during Design Day week, it was
populated using a more precise soldering iron and a better SurfBoard. Thinner wires
were also used to connect the SurfBoard to the PCB. Initial signals provided to the
board did not provide correct results, but after troubleshooting using a multimeter,
function generator, and oscilloscope the error was found. A resistor tied between Vref
and ground to fix the error. The resulting design responded correctly and an in-depth
discussion testing, troubleshooting, and final simulations can be found in Chapter 4. The
final design is displayed below in Figure 11 with the red SurfBoard resting on the PCB
and the added resistor visible at the bottom center of the PCB.
Figure 11: Functional ECG PCB
30
Chapter 4 – Final Testing and Proof of Functionalit y
4.1 – Testing Goals
The primary testing objective was determining if the ECG system was capable of
amplifying small signal inputs from CardioSim II. CardioSim II is an ECG signal
simulator provided by Mr. Semig capable of replicating signals produced by the human
heart with various heart rates and abnormalities. A secondary objective was to show
that the system would be able to filter those inputs through both the low-pass filters on
the output and the Right Leg Drive feedback loop. Finally, the device had to be
powered by a 9 Volt battery which the circuit would regulate down to 5 Volt to ensure
that all of the chips operated within their operational voltage ranges.
4.2 – Testing Set Up
Since this project is focused on a medical application, it is not expected to have
to operate in extreme conditions such as high temperature. All measurements were
done in a room-temperature environment, roughly 72°F. In order to test an individual
component, it was air wired to connect a bench power supply, oscilloscope, function
generator and any other required connections. Show in Figure 12 is the air wire set-up
for the INA333 that was tested. After testing individual components for functionality,
each component was soldered to the PCB, and then the board was connected to a
power supply. Finally, once all components were determined to work and soldered to
the PCB, a 9V battery was used to power the board. The included power step down
circuitry, using the TPS5410, restricted the power to 5V to supply the ECG circuit. The
final inputs to the board were supposed to be supplied by the CardioSim II that would
provide simulated heartbeat signals for a person’s right arm, left arm and right leg. The
simulator was never functioning properly to act as inputs, so the inputs for simulation
were supplied by a function generator.
31
Figure 12: Air-wiring the INA333
4.3 – Verification of Amplification
To verify that the circuit was amplifying properly, several steps were taken to test
the amplification of the INA333 both with and without the rest of the circuit. Described
above, air-wiring was used to connect the INA333 to a power supply and function
generator, which supplied inputs. This yielded good results shown in Figure 13. Once it
was verified to work outside the circuit, the INA333 was soldered onto the SurfBoard. A
SurfBoard was used because the footprint on the fabricated board was slightly too large
for the INA333, and the SurfBoard was attached to the printed circuit board using short,
thin wires. Again, function generators were used to simulate the inputs to the finished
circuit since the CardioSim II was not working correctly. The final output using inputs
from the function generator is shown in Figure 14, which is the final output for the board.
This particular figure used the passive filtering option discussed in the next section of
this report. The output is a clean amplification of the difference between the two inputs.
In the figure, yellow and green are inputs and the red is the output. The inputs are
slightly out of phase with each other. This caused a slightly larger dip in the QRS
complex as seen in the figure, but that wasn’t due to the performance of the board.
Overall, the amplification was working as intended.
32
Figure 13: INA333 air-wire amplification results
Figure 14: Vout of the entire PCB design
33
4.4 – Verification of Filtering
After the INA333 amplified the input signal, the result needed to be filtered to
reduce noise and make the heartbeat more visible. This was achieved through both a
passive and active filter on the PCB. Since the CardioSim II was not working correctly,
below are two images that show a filtered input from the function generator. The first
image, in Figure 15, displays the passive filter for the device. This is comprised of a
resistor and capacitor. The second image, in Figure 16, shows the filtered result for an
active filter. Both of these filters are shown to reduce some of the high-frequency noise
that gets into the circuit. In both figures, the yellow line is the input and the green line is
the output. As can be seen, the yellow line is thicker and has more jagged edges than
the green line, this is due to less high-frequency noise on the signal at the output.
Although both filters work to reduce high-frequency noise, the performed tests produced
no visible difference in quality between the passive and active filters.
Figure 15: Passive filter
34
Figure 16: Active filter
4.5 – Verification of Power Regulation
Although the battery is called a ‘9 Volt battery’, the output of the battery is not
always 9 Volts. The voltages in the battery were observed to change from 11 Volts
down to 8 Volts; this was due to the battery running out of charge. Due to this
observation, the voltage at the input node was not taken into consideration, but only the
voltage at the end of the power regulation. This voltage needed to be as close to 5V as
possible to power the circuit properly. As shown in Figure 17, the output voltage of the
power regulator is very close to 5V. Also, the circuit required a reference voltage at
‘mid-supply,’ which means halfway between the lowest voltage and highest voltage. In
this project, the reference voltage was supposed to be 2.5V. This reference voltage is
measured in Figure 18. The multi-meter shows the reference voltage which is close to
2.5V. These measurements ensure that the circuit could be powered with a 9 Volt
Battery, and the integrated circuits would receive the proper voltages, after the battery
was regulated, to work correctly.
35
Figure 17: Vout for the power regulator
Figure 18: Common mode voltage
Chapter 5 – Summary and Conclusions
5.1 Budget and Cost
Throughout the semester, the project’s cost stayed within the $500 budget
given by the College of Engineering. All of the chips were available through Texas
Instruments website as free samples, and the electrocardiograph simulator (CardioSim
II) was provided by Mr. Semig at no cost. PCB fabrication comprised most of the spent
budget. There were six boards fabricated, four stability and two ECG, at a cost of $33
36
per board for a pre-shipping total of $198. Also, all components and parts were ordered
using standard ground shipping so no extra shipping cost was added to the final budget.
Table 2 illustrates the final project cost breakdown.
Table 2 Final Project Cost
Item Cost ($) Shipping($) Total ($)
2 PCBs for Stability 1 Circuit 66 18.23 84.23
2 PCBs for Stability 2 Circuit 66 18.23 84.23
Miscellaneous Parts for stability 14.85 7.35 22.20
PCB of ECG Circuit 66 18.23 84.23
SSOP to DIP Adapter 8-pin 5.90 12.32 18.22
Miscellaneous Parts for ECG 51.28 0 51.28
Microchips for stability and ECG
board
0 0 Provided by TI
CardioSim 0 0 Provided by TI
Total 270.03 74.36 344.39
5.2 Schedule
Design Team6 stayed on the schedule for the majority of the project. The Gantt
Chart was developed in the beginning of the semester and was displayed in Chapter 2.
The weekly goals were intended to be finished by team members. However, the project
schedule was delayed by the longer turnaround and shipping times than expected.
There were also times team members had to travel throughout the semester, which
created a discrepancy between the planned schedule and when the work was actually
accomplished.
37
5.3 Executive Summary
The final objective was to fabricate a working ECG board for Texas Instruments.
This goal was accomplished, but the final design wasn’t as robust as expected. Full
functionality of the board was present, but two mismatched footprints and the
requirement of an additional resistor for full functionality left the PCB design the original
solution aspired to build unfinished. The resistor was added using the test points added
to the layout for hardware debugging, a wire was used to attach the tantalum capacitor
to the PCB, and a SurfBoard with the correct INA333 footprint was used to attach the
INA333 to the board. These mismatched footprints and the missing resistor necessary
to create a fully-functional, well-designed ECG were discovered before the deadline.
Unfortunately, the extended fabrication and shipping times associated with obtaining
printed circuit boards meant minor changes couldn’t be implemented into the final
design.
Even with the design having a few slight flaws, many positive results were
obtained. A functional product was developed within budget and, with the mentioned
minor tweaks, behaved as expected for an ECG board. The PCBs were developed well
within the projects allotted funds, with over $150 of the original $500 budget remaining.
A more well-rounded design has been realized after testing the finished product; this
design could have been ordered within the budget if the deadline was extended. Also,
two stability boards of use to TI were fabricated, with accompanying simulation and lab
test results. The TINA-TI schematic files, PCB Artist schematic files, and PCB Artist
layout files are all saved and can be made readily available to the sponsor. This allows
for future teams to correct the minor mistakes and add enhancements to the base
product.
5.4 Conclusions and suggestions for future work
After undertaking and completing a PCB design solution, many conclusions can
be drawn to help future project teams with PCB design. The importance of designing a
solution prototype as early as possible in the project’s life-cycle cannot be stressed
enough. The fabrication and shipping times will create time throughout the project to
work on secondary and tertiary objectives. Using a software simulator like TINA-TI is
38
also a necessity. Working simulation results greatly increase the probability that the
board will function correctly once fabricated. This can sharply decrease the number of
practical revisions the board must go through, greatly decreased cost and time to
produce a working solution.
Any teams working on ECG design solutions should understand the importance
of minimizing disruptions to their circuitry, noise reduction, and stability in their design.
ECG signals are generally on the millivolt and microvolt scale. Therefore, precision
components must be selected and interference minimized. The three lead design
created for Texas Instruments was feasible on a two-layer board, but for larger ECG
designs, such as the 12-lead ECG, working with four and six layer boards will be
beneficial to improving performance of the finished product. It’s also important to
remember a stable, regulated power supply for the circuit will improve performance as
well as help prevent burning out portions of the circuitry. Many of the components
necessary will be highly sensitive and prone to burning out if supplied with too much
voltage or current.
39
Appendix I: Technical Contributions
Matt Affeldt
Throughout this project Matt began by working on the
simulation and layouts of the Stability board. Since
he had prior experience doing Printed Circuit Board
design he was responsible for introducing the rest of
the team to the process. Before the first stability
circuits could be laid out, they needed to be
simulated. Since Matt and Alex were the first two to
test out TINA-TI, it was determined they would do the simulations. Throughout this
process Matt and Alex worked together to create the specified simulations for the
OPA627 and the OPA365. In order to do the simulations, a schematic in TINA-TI
needed to be created, and then the simulation profile needed to be defined. This
process was relatively straight forward; the most difficult part was to create the
simulation profile since the software was new to both Matt and Alex. After the stability
circuits were completed, Matt provided some guidance while the others worked on
creating the simulations, schematics and layouts for the final ECG board. Once those
were completed, Matt began assembling the boards. Since Matt had previous
experience soldering surface mount components, it made the most sense for him to
work on the delicate parts of the ECG assembly. Again, the process of assembling the
boards was relatively straight forward; however it was very time consuming to deal with
such small components. Once the board was completed, Matt and Alex began testing
and debugging the circuits. Although there were several errors, some stemmed from
the design and some stemmed from the assembly process, the two successfully created
a working ECG board and were able to get lab data to show the circuit was working.
This data included results for filters, the INA333 amplification as well as the power
regulation to bring the 9V battery down to the required 5V.
40
Derek Brower
Due to the ECG project having two phases,
practicing PCB design with stability circuits and
ECG design, Derek’s contributions varied
across the project phases. During the stability
PCB design, Derek primarily worked on the
layouts and helped assemble and test the
finished product. While working on the ECG
board, he ran multiple simulations of the finalized schematic and coproduced the layout.
Derek utilized the stability phase of the project to familiarize himself with PCB
Artist and the layout process. A PCB Artist quick-start guide was provided by the project
sponsor, Mr. Pete Semig, for reference while learning how to produce a layout in PCB
Artist. This reference was used by Derek to create the layout for the feedback stability
circuit. The stability layouts went through a singular revision from Mr. Semig where
additional design standards and layouts techniques were learned. Derek also helped
assemble the board and contributed to running hardware simulations in an effort to
ascertain stability results. The obtained results matched the theoretical results obtained
by the group through schematic simulation in TINA-TI for both stability boards. A
PowerPoint presentation was prepared by the group, using the simulation results and
experimental results, to show Mr. Semig the boards indeed performed as expected.
Derek contributed ideas to the creation and improvement of the ECG schematic
based on simulation results, but most of the original circuit design was done by Phil and
Alex. Derek assisted Nick in running simulations on the original circuit design and
subsequent updates. After a few edits of the original design, the finalized schematic
consistently matched expected values through simulation. Mr. Semig approved the final
circuit design and the layout process began. Derek co-designed a majority of the layout
with Phil. The layout went through two revisions designed to minimize disruption to
important signals and to enhance sensitive circuitry performance by notching the ground
plane. Derek was involved in the hardware debugging post-fabrication, but most of that
41
work was performed by other group members while he helped finish the non-technical
deliverables.
42
Phil Jaworski
Phil’s technical roles during the course
of the semester involved the assembly
and testing of the initial stability circuits,
and the schematic design and layout of
the final board. For the stability
designs, Phil was responsible for
ordering each component that needed
to be implemented on the board,
soldering the components, and using
the scope to capture waveforms to show that it was functional. These tasks proved to
be tedious, as the soldering of surface mounted components and very small amplifiers
are difficult and require absolute precision. After the boards were finalized, tests were
run to compare the signals from the physical board to the signals we were getting from
the simulations to be sure they were functioning properly. Some problems occurred
with getting the proper signals at first, but after multiple attempts, we were able to get
them in working order. For the final board, Phil was responsible for designing the
schematic that would eventually be the floor plan of our project, and laying out the
physical location of each component on the PCB. The main tool used during this
process was the program recommended for our use, PCB Artist. After attempting
multiple designs and techniques for the optimal functionality of the board, the team
agreed on a design. The team initially thought a four layer board would be used, but it
was agreed that using a two layer board would be simpler, and Phil began design of the
final layout in PCB artist. This task proved to also be difficult due to inexperience with
PCB layouts and PCB software, and also the fact that this project was extensive. One
main goal that needed to be achieved during the layout was for it to be simple, so it
could be viewed from overhead and easily understood in case errors had to be tested
for, or to explain how it operates to somebody else.
43
Jung-Chun Lu
The project was collaboratively
accomplished all challenges that the
design team faced. During building of
the stability and ECG board, the
technical roles would divide up tasks
into five different aspects: schematics,
simulation, PCB layout, assembly and
hardware debugging. Each member of
the team contributed two technical roles
with another one member helping one of them.
At the beginning period of project, Jung-Chun mainly focused on the schematic
and assembly when building stability boards. For the schematics, he transferred the
schematics from TINA-TI to Printed Circuit Board (PCB) Artist. The schematic of design
was which everything start so some important considerations were helpful to him.
Although PCB layout did not really required a schematic, an inexperienced user was
suggested to start with a schematic. In this way, the errors of tracing would be easily
examined for another member that converted schematic to PCB layout. Also, creating
the correct footprints for each components and pads were significant. With the help of
Alex, the schematic was ensured that the footprint of surface mount components, test
points and power pads could be soldered on the PCB. Once the board fabricated, Jung-
Chun and Phil worked together on assembling four stability boards. All the surface
mount dimensions stayed above 08x05mm and handing soldering technique increased
the difficulty with small components. Despite complexity of handing soldering, Jung-
Chun and Phil could manage the struggle.
During the mid-phase of project, Jung-Chun assigned to simulate the TINA-TI
schematics built by another member. The transient analysis was ran and showed the
convergence problem at the first few try. However, the problem was overcame by
adding a large resistor (10MΩ) and a ground connecting to it at the output stage of each
operational-amplifier. With the help of Derek, changing the TPS chip to regular power
44
supply and inverting the INA333's connection reduced the simulation time and output of
INA333, respectively. The simulation results were discussed in the earlier chapter.
Furthermore, Matt and Jung-Chun assembled the components of ECG board. Again,
without the suitable equipment, the difficulty enlarged to solder all surface mount
components, but we overcame the defy with circumspect soldering.
45
Alex Volinski
The first technical contributions made
to the project by Alex were in simulating the
stability circuits given to the group by the
sponsor. The original files were written up
with placement holders for the parts in TINA-
TI, and needed to be completed with real
components and simulated. The work Alex
puts towards this included the addition of preexisting parts from the library such as the
resistors and capacitors, as well as creating new parts that did not already exist in the
libraries including the operational amplifiers. After creating the proper circuits and with
working components, Alex worked along with Nick in simulating the expected results of
these circuits using TINA-TI’s simulators. This allowed for the group to get a specific
idea of what the output should be in the lab when testing these boards after being built.
Once the boards were simulated, the next step was to create schematics of these
boards using PCB Artist. The creation of the schematic was undertaken by Alex
working with Matt. The creation of the schematic was achievable quickly for the stability
circuits because the TINA-TI files had been created already. Creating the schematics
included piecing together all the components properly, as well as creating proper power
and ground connections throughout the circuit.
In between working on the stability boards and the actual electrocardiograph
demonstration board, the whole design team worked closely together on the creation of
a circuit design to use for the demonstration board. This went through multiple revisions
with the sponsor and with the team until a final design was decided upon.
Once design on the electrocardiograph demonstration board began, Alex took on
the role of creating the schematics again after realizing he was good at it from the
stability board portion of the project. This time, he worked alongside Phil in putting the
group’s circuit design into PCB artist and making sure that all the components were
connected to each other properly, as well as to power and ground. This was much
more difficult than in the stability circuit schematics because of the sheer amount of
parts and problems that could arise if something is connected even slightly wrong. The
46
other large aspect of the electrocardiograph demonstration board that Alex worked on
was testing the boards. After realizing he had done a lot of work on the computer in
software and simulations, he wanted to get into the lab and actually work with the
circuitry and hardware portion of the project. Working alongside Matt, Alex tested all the
aspects of the boards in the lab. This included the testing of each of filters around every
input and output area to make sure the signals were being generated and filtered
properly, as well as testing all the chips to see if they were working as intended. The
testing portion of the project was done very closely with the group members populating
the board, because the group wanted to make sure that each component was working
before moving on to the next one.
47
Appendix II: References Software
PCB Artist Software
http://www.4pcb.com/free-pcb-layout-software/index. html
TINA-TI Software
http://www.ti.com/tool/tina-ti
PCB Artist Tutorial
http://www.4pcb.com/media/PCBArtistTutorial.pdf
Specialized Footprints for PCB layout
Shield Inductor
http://datasheetz.com/data/Inductors,%20Coils,%20Ch okes/Fixed/513-1409-1-
datasheetz.html
Tantalum Capacitor
http://lecs.cs.ucla.edu/~girod/tags/SensorModule/do cs/Capacitors_AVX_tant.pdf
Schottky Diode
http://rohmfs.rohm.com/en/products/databook/datashe et/discrete/diode/schottky_
barrier/rb162m-60.pdf
Datasheets
OPA 365 Operational Amplifier
http://www.ti.com/lit/ds/symlink/opa365.pdf
OPA 627 Operational Amplifier
http://www.ti.com/lit/ds/symlink/opa627.pdf
INA333 Instrumentation Amplifier
48
http://www.ti.com/lit/ds/symlink/ina333.pdf
OPA333 Operational Amplifier
http://www.ti.com/lit/ds/symlink/opa333.pdf
TPS5410 Step Down Converter
http://www.ti.com/lit/ds/symlink/tps5410.pdf
Research Resources
ECG PowerPoint provided by Mr. Pete Semig http://ece480group6.wordpress.com/documents/ PCB Artist Quickstart PowerPoint provided by Mr. Pete Semig http://ece480group6.wordpress.com/documents/ Texas Instruments E2E Community http://e2e.ti.com/
49
Appendix III: Technical Attachments
Figure 19: Stability One Schematic
Figure 20: Stability One Layout
50
Figure 21: Stability Circuit 1 (Open Jumper) Stable Operation Simulation
Figure 22: Stability Circuit 1 (Closed Jumper) Unstable Oscillations Simulation
51
Figure 23: Stability Circuit 1 (Open Jumper) Stable Operation Oscilloscope Capture
Figure 24: Stability Circuit 1 (Closed Jumper) Unstable Oscillations Oscilloscope
Capture
52
Figure 25: Stability Two Schematic
Figure 26: Stability Two Layout
53
Figure 27: Stability Circuit 2 (Open Jumper) Stable Operation Simulation
Figure 28: Stability Circuit 2 (Closed Jumper) Unstable Oscillations Simulation
54
Figure 29: Stability Circuit 2 (Open Jumper) Stable Operation Oscilloscope Capture
Input is the blue step, Output is the yellow curve
Figure 30: Stability Circuit 2 (Closed Jumper) Unstable Oscillations Simulation
Oscilloscope Capture
Input is the blue step, Output is the yellow curve
55
Figure 31: TINA TI Simulation Schematic
56
Figure 32: TINA-TI Passive without RLD Simulation
57
Figure 33: TINA-TI Passive with RLD Simulation
58
Figure 34: Final ECG PCB Artist Schematic
59
Figure 35: Final ECG Layout