Created by: ECE 480 Design Team 6
Attention: Dr. S. Ratnajeevan H. Hoole
Subject: ECG Demonstration Board Solution Progress Report 2
Date: November 20th, 2012
Statement of Purpose
This progress report was created to provide the reader an understanding of the
work accomplished towards the completion of an Electrocardiograph (ECG)
demonstration board for Texas Instruments. This progress report outlines work
accomplished since our previous progress report delivered on October 25th. We are
currently on schedule, and this report outlines the technical work completed, nontechnical work completed, as well as remaining technical work to be done. The schedule
for the remaining work has changed from that set at the beginning of the semester due to
the extended fabrication and shipping time of our final PCB design. Most of the
remaining work will be completed during Design Day week once our Advanced Circuits
board arrives.
Technical Work Completed
Designed the ECG schematic
We built our ECG schematic from scratch based on PowerPoint slides provided
by Mr. Semig, and our own research and feedback from Mr. Semig after each draft. For
schematics, we drew the original schematic in TINA-TI then transfered it to PCB Artist.
The TINA-TI schematic is for simulations and the PCB Artist schematic creates a
correlation between the schematic and layout views. The circuit was built using the
INA333, TPS5410 and OPA2333. These chips were available as free samples from Texas
Instruments (TI). The ECG schematic underwent three revisions before being transferred
into a layout. The PCB Artist schematic is attached as the second to last page of this
report.
The revisions included adding common node voltage capacitors to the input of the
INA333, an RC filter and active filter to the output, RC filters to the input, a 9V step
down low-dropout (LDO) power supply using the TPS5430, switching the TPS5430 to
the 5410 for better efficiency and ease of soldering, and adding decoupling capacitors
between power and ground.
Designed the ECG layout
The ECG layout was built from our schematic and is currently ordered. We are
awaiting arrival of the board to populate and test performance. The layout underwent one
official revision through Mr. Semig, which he felt was sufficient due to the minor
changes needed to be made.
Mr. Semig told us to check the total current our LDO power supply needed to
supply 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 did not place jumpers at each end of the filter,
so we added additional jumpers. This afforded us the ability to isolate the filter we were
not 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. Cutting the ground plane beneath the inverting nodes prevents current from
running through the ground plane underneath these nodes. As these are sensitive areas of
our circuit, preventing interference from current in the ground plane to these nodes is
worth increasing ground plane impedance by cutting notches under the nodes.
These changes may sound extensive and severe, but they were mostly minor
adjustments made on the layout. After all changes had been made, we all looked the
layout over and ordered it. The finished layout is attached as the last page of this
document.
Ordered the INA333, OPA2333, and TPS5410
We ordered free samples of all the chips needed to populate our ECG printed
circuit board (PCB). We have not ordered the components because our layout was
finished and ordered on 11/19. Now that our layout is finished, we have final component
values and will order them shortly. This is not an issue because components arrive
quicker than our ECG PCB will.
Tested CardioSim2 with the oscilloscope
We are currently testing inputs and outputs with the CardioSim2. The CardioSim2
can be connected to at ten points. Each point represents an area of the body where an
electrode is attached in a 12-lead ECG machine. A lead is a pairing of electrodes that
produces a voltage signal useful to mapping activity. So, a 12-lead ECG uses the 12
informative pairings of these ten electrodes. CardioSim2 provides the electrodes to
simulate up to these 12-lead ECGs as well as heart irregularities like an arrhythmia.
Our board will be a three lead ECG, so we only need to worry about the signals
pertinent to a three lead ECG. These include the Right Leg (RL), Right Arm (RA), and
Left Arm (LA) electrodes. The pairings are RA RL, RA LA, and RL LA. We tested all of
these pairings and only received noise. When we fed a signal from the function generator
through the Right Leg, we read the signal at the right and left arms. However, the voltage
difference was still zero. Since ECGs map the heart using the voltage difference between
the RA and LA, we are not getting correct results. Additionally, we tried pairings of
electrodes used in 12-lead ECGs and even abnormalities like an arrhythmia. Nothing
produced correct results. Online documentation only exists for CardioSimVII. So, we
have talked to Mr. Semig and will continue testing. Currently, the CardioSim does not
work.
Non-Technical Work Completed
Application Note
Each group member wrote an individual application note, which was turned in to
our facilitator Professor Hoole. Following is each group member’s topic.
Matt Affeldt’s topic was electrical considerations when creating a printed circuit
board (PCB) layout. Derek Brower’s topic was creating a layout in PCB Artist. Phil
Jaworski’s topic was using TINA-TI simulation software. Jung-Chung Lu’s topic was
creating a library and component in PCB Artist. Alex Volinski’s topic was
electrocardiography and design.
Technical Presentation
Our group gave a technical presentation on printed circuit board (PCB) design.
Topics covered in the presentation included layout, assembly, and electrical
considerations as well as software flow. Software flow covered the basics of designing a
PCB schematic and layout in software. Layout considerations discussed floor planning,
routing, and board options available to a PCB designer. Assembly considerations
examined component types and assembly techniques. Finally, electrical considerations
covered material important to more advanced PCB designs including impedance tradeoffs, antennas, and stray capacitance.
Remaining Technical Work
Determine how the CardioSim2 functions
We need to determine how to receive the correct outputs for signals of the heart
from CardioSim2. This is essential because CardioSim2 will supply the inputs and Right
Leg Drive to our ECG board.
Order components to populate ECG
The resistors, capacitors, diodes, inductors, and test points necessary to populate
our ECG need to be ordered. The chips are already on order.
Populate and test the ECG
Upon receiving our board and components, we need to solder the board together
and run simulations using CardioSim2. The results will be a large part of our final
presentation on Design Day and our final written report.
Organize the data and incorporate it into our final report and presentation
The results of our ECG tests must be organized and analyzed. The results of this
will be incorporated into the final reports for the class.
Important Parts to be Used
Part
Manufacturer
Quiescent Current
Supply Voltage (Vs)
Input Voltage Range
Part
Manufacturer
Quiescent Current
Supply Voltage (Vs)
Input Voltage Range
Part
Manufacturer
Max Output Current
Max Efficiency
Input Voltage Range
OPA2333
Texas Instruments
50 uA
7 Vmax
-0.3V to 0.3V
OPA2333
Texas Instruments
17 uA
1.8V to 5.5V
-0.1V to 0.1V
TPS5410
Texas Instruments
1.0 Amphere (continuous)
95%
5.5V to 36V
Final ECG Schematic
Final ECG Layout