Created by: ECE 480 Design Team 6

Attention: Dr. S. Ratnajeevan H. Hoole

Subject: Midway Progress Report on ECG Demonstration Board Solution

Date: October 25th, 2012

Statement of PurposeThis progress report was created to provide the reader an understanding of the

work accomplished towards the completion of the creating an Electrocardiograph (ECG) demonstration board for Texas Instruments. A proposed schedule was created by our sponsor from Texas Instruments, Mr. Pete Semig, at the beginning of the semester. We are currently on schedule, and this report outlines the work completed, problems encountered, as well as remaining work to be done with the proposed schedule for said work.

Technical Work CompletedMr. Pete Semig, our design team sponsor from Texas Instruments, chose two

stability circuits TI intends to use for future applications for us to layout, fabricate and test. The purpose of making these boards was to provide our team with smaller projects to practice the schematic design, layout design, fabrication process, populating PCB boards and testing final PCB designs. Both circuits were designed with switches which, depending on whether they were open or closed, put the boards in a stable or unstable state.

Edited and ran Error Rule Check (ERC) on the TINA-TI schematics Mr. Semig ProvidedPete provided us with the TINA-TI schematics for the two stability boards as well

as changes we would need to make to the boards. For stability circuit 1, we removed the series capacitor from the design, increased the value of the voltage divider resistors, and changed the op amp to the OPA 365. The OPA 365 was not in the TINA-TI library, so we uploaded the macro to TINA-TI from Texas Instrument’s website. TI has macros for almost every part they make on their website. For stability circuit 2, we simply changed the value of the load resistor to 10 kΩ. We ran ERC to ensure the schematics had no errors in wiring after each change. Then, we transferred the schematics to PCB Artist. This allows us to create the layout for the schematics. The PCB Artist schematics are attached next to their corresponding layouts after the layout section.

Created the layouts for the two stability boards in PCB Artist These layouts were made from scratch by our group and required us to learn PCB

Artist. Some components were in the PCB Artist library already, but we created libraries for the banana jack, test point, and op amp. Pete gave us the parameters for the banana jack and test points in one of our weekly teleconferences, and we obtained the parameters for the op amp from its datasheet on TI’s website. In order to make a new component to use in PCB Artist, we created a schematic and PCB symbol for each part in the library manager. Both symbols needed to be made so we could place our part in the schematic and run ‘Schematic PCB.’ The ‘Schematic PCB’ tool allowed us to transfer our schematic to a layout view with the click of a button. Schematic view and layout view symbols can be seen in the attached images on the next two pages.

After creating all components not already included in the PCB Artist library, we produced the layouts for both circuits 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. We also specified that our

signal traces would have a width of 15 mils and the power and ground traces a width of 25 mils. We arranged the rest of our components and traces around these parameters with a design intended to minimize overall board area and the length of traces between components. After creating the layouts, we ran Design Rules Check (DRC) to make sure our layouts passed all design rules necessary for functional fabrication.

Staility One Schematic (below)

Stability One Layout (above)

Stability Two Schematic (below)

Stability Two Layout (above)

Fabricated the PCB Boards and ordered componentsPCB Artist was chosen to create the layouts for the stability boards and for our

future ECG circuit due to the ease of ordering the boards for fabrication. The boards can be ordered directly through the PCB Artist software with a discount for students. Under Settings>PCB Configuration we can specify this is a student 2-layer basic board, the turnaround time for fabrication and the number of boards we want to order. 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. We chose a one week turnaround time and our boards arrived a week later. We also ordered the components we would use to populate the boards as well as components necessary for our ECG board.

Simulated the schematics in TINA-TIWe ran transient simulations on the TINA-TI schematics with a one volt step

input to discover what the response of each circuit would look like under stable and unstable conditions. This can be performed within TINA-TI by specifying 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. We saved our simulation results from the analyses to compare to our lab test results on the boards. The next two pages show the results.

Stability One Open Open Jumper (Stable Operation)

Rising Edge of Input step

Stability OneClosed Jumper (Unstable Oscillations)

Rising Edge of Input step

Stability TwoOpen Jumper (Stable Operation)

Rising Edge of Input Step

Stability TwoClosed Jumper (Unstable Oscillations)

Rising Edge of Input Step

Populated and tested the boardsOnce all our parts and the PCB boards had arrived, we populated the boards and

tested the response using a function generator, power supply and oscilloscope. Initially we experienced a great deal of noise and oscillation within our boards, but, after adjusting the oscilloscope and briefly placing a 100 pF capacitor between Vin and ground, we were able to eliminate oscillation and most of the noise caused by interference. To provide a clearer picture we enabled averaging. This smoothed the minimal remaining noise. Our lab results closely matched our simulation results and we were able to confirm we had fabricated working circuits. The percent overshoot in the lab was within 5% of the percent overshoot calculated by the simulations. This held true for both circuits. Mr. Semig was very pleased we were able to successfully fabricate the boards and was very interested in our lab results; we provided him with a PowerPoint including screenshots of our simulations and lab results.

Received CardioSim2 and used the oscilloscope to test various outputsWe have received CardioSim2 and have hooked it up to the oscilloscope to view

various outputs it can send to our ECG board. We want the output of the CardioSim2 behaving in a linear fashion. The output signal cannot be too large or small because our op amps will no longer behave like op amps in our circuit. This is due to the low power zero drift OPA2333 we are using. This op amp cannot handle large signals. We will continue testing this tool.

Non-Technical Work Completed

Pre-proposal and proposal writtenAs a group, we wrote a proposed solution for our project. We wrote a rough draft

pre-proposal outlining the proposed project solution. This document was revised and became our final proposal. The document included background on why Texas Instruments assigned the project to us, background on electrocardiography, customer requirements, our proposed solution, risk analysis, project management, project schedule, and cost. The schedule included a Gantt chart we created to visually map deadlines for the semester.

Proposal PresentationWe gave our proposal presentation to the class to develop our public speaking

skills in preparation for Design Day. The topics covered were the same as in the written proposal and were divided evenly among group members.

Program GuideWe wrote a program guide for our project. This guide gives a brief written

synopsis of our project and includes a team picture with names and roles listed, sponsor logo, and project picture.

Problems Encountered

Problems obtaining exact percent overshoot numbers for Mr. SemigOriginally Mr. Semig wanted us to obtain numbers for the percent overshoot in

our simulations as well as our tests on the boards in lab for comparison. The test points we ordered had not arrived and we obtained our lab results by improvising and wrapping a wire through the points where our inputs, grounds, and test points would be. This allowed us to graph a response with averaging enabled, but did not allow us to obtain very accurate overshoot numbers to compare.

Remaining Technical Work ScheduleAt our last meeting with Mr. Semig we outlined a schedule for creating our ECG

demonstration board now that we’ve finished the stability boards. This schedule was updated from our original Gantt chart to reflect current progress.

Deliverables for October 29th meeting-performed tests on the INA333 in lab using single and dual band power supplies

to measure the response with varying voltage levels-measure the outputs CardioSim2 provides using the oscilloscope-design our initial ECG circuit-create the schematic in TINA-TI

Deliverables for November 1st meeting-an updated ECG schematic including any changes Mr. Semig suggests upon

viewing our first draft of the design- the initial PCB Artist layout for our ECG board

November 1st-2nd

-create an updated PCB layout including the any suggested changes made by Mr. Semig

-order PCB boards as well as components necessary to populate the boards

Deliverables for November 8th meeting-Discuss the status of our boards and test results-It is likely this meeting may be moved or an additional meeting set depending on

the arrival of our boards-Goal is to populate and test board functionality upon arrival

Deliverables for November 15th meeting-Provide Pete with our simulation results and lab results-Discuss proposed changes to our schematic and layout with Pete based on

simulations and lab test results

November 15th-16th

-Implement changes to our schematic based on our test results-Implement changes to our layout based on our test results

-Order final ECG board

November 22nd-Thansgiving Day-No meeting planned-may schedule a check-in meeting at the start of this week or the following week

November 29th meeting-Have a populated final ECG board-Have lab test results and simulation results to discuss with Pete-Discuss the results-Troubleshoot any problems, non-ideal results or errors with Pete

Week of Design Day-Finish any preparations on our ECG board for design day

Design Day-Present finished product

Important Parts to be UsedPart OPA2333

ManufacturerTexas Instruments

Quiescent Current 50 uASupply Voltage (Vs) 7 VmaxInput Voltage Range -0.3V to 0.3V

Part OPA2333

ManufacturerTexas Instruments

Quiescent Current 17 uASupply Voltage (Vs) 1.8V to 5.5VInput Voltage Range -0.1V to 0.1V