Spring 2016 A-TeChToP Research Project

By: Cody Dunn (Project Manager)

Omar Rojas (Systems Engineer: Emphasis Old Sensors)

Robin Yancey (Systems Engineer: Emphasis ECG) 

Rose Leidenfrost (Systems Engineer: Emphasis EEG)

Stephen Cortez (Electronics Engineer: Emphasis ECG)

Marena William (Electronics Engineer: Emphasis EEG)

Mimy Ho (Manufacturing Engineer)

Project Manager Research

Cody Dunn (Project Manager)

Source Material

  1. A-TeChToP Final Documentation, Project Budgets, 5/10/15, http://arxterra.com/atechtop-final-documentation/
  2. A-TeChToP Final Documentation, Project Completion Status, 5/15/15, http://arxterra.com/atechtop-final-documentation-2/
  3. A-TeChToP Final Documentation, Project Status, 5/10/15, http://arxterra.com/atechtop-final-documentation/
  4. A-TeChToP Final Video, 5/15/15, http://arxterra.com/atechtop-final-video/
  5. 5. A-TeChToP Final Video Spring 2015, 5/16/15, https://www.arxterra.com/atechtop-final-video-spring-2015/
  6. A-TeChToP Project Requirements, Project Level 1 Requirements, 4/5/15, http://arxterra.com/atechtop-project-requirements/
  7. A-TeChToP Requirements: Level One and Level Two, Level One, 4/6/15. http://arxterra.com/atechtop-requirements-level-one-and-level-two/
  8. Bioengineering Project Final Documentation, Project Requirements, 12/15/14, http://arxterra.com/bioengineering-final-documentation-atechtop/
  9. Verification of Budget Requirements, Component Acquisition and Budget Data Sheet, 5/8/15, https://www.arxterra.com/verification-of-budget-requirements/

Additional Sources:

[1] R. Picard. (2012). EPIBAND: Electrodermal and Seizure Event Alert [Online]. Available: http://www.epilepsy.com/sites/core/files/atoms/files/ST-5-Picard.pdf

[2] J. Crimando. (1999). EKG Arrhythmia Review [Online]. Available: http://www.gwc.maricopa.edu/class/bio202/cyberheart/ekgqzr0.htm

[3] Galen Carol Audio. (2007). Decibel (Loudness) Comparison Chart [Online]. Available: http://www.gcaudio.com/resources/howtos/loudness.html

Review of Literature

Analysis of Past Level 1 Requirements

Requirement Evaluation Rubric Used for the Tables:

  1. Is the requirement, Quantitative, Verifiable, and Realizable?
  2. Is the requirement located at the correct level (1 – Program/Project)
  3. Is the requirement response to a higher level requirement or customer’s objective (Requirement Flow Down)? Is the linkage clearly defined?
  4. Does requirement provide links to source material?
  5. Does the requirement move the design process forward?
  6. Are equations used to calculate a requirement provided and are answers correct?
  7. The requirements that are missing are the hardest to discover and will be factored into your evaluation.
  8. Is language in the form of a requirement?
  9. Avoid multiple requirements within a paragraph. (i.e., breakup statements that contain multiple requirements)


Spring 2016 Discussion of Requirements from Spring 2015 Wednesday:

The group generally wrote requirements on the proper level and worded them appropriately. However, this was not the case for requirements four and five because they used the word “should” instead of “shall.” The group often lacked citations to research articles and references to the older A-TeChToP project. The first requirement appears to be on the wrong level because it is too technical and would not have level two requirements below. The second requirement was flawed because the verification involved monitoring for “accuracy” and “consistency” among the output sensor signals. A more quantitative test would be to determine a percent error between A-TeChToP’s output signals and a standard medical equipment’s output signals. The third requirement was similar to the second in that it was not quantitative. One way to test whether the device is water resistant would be to submerge it under an inch of water for five seconds.

The requirements could be improved by adding requirements concerning what signals are to be measured. It is also important to mention the device should be capable of alerting parents and doctors as to the health of the child using visual cues on the Arxterra control panel. The requirements cover the safety and comfort of the child, but do not stress the purpose of having A-TeChToP (to monitor the biological signals of a child), which is fundamental to level one requirements.


Spring 2016 Discussion of Requirements from Spring 2015 Friday:

Similar to the first group, this group should change the requirement wording to use “shall” instead of “should.”

This group did a much better job of supporting their requirements with sources and documentation from the prior A-TeChToP project. Furthermore, all of the requirements appeared to be quantifiable, verifiable, and reasonable.

Some of the requirements did have room for improvement. For example, the first requirement should be split into a few requirements based on the number of measurements included in the requirement. The seventh requirement did not include a source. It may have been useful to mention a source that cites the importance of real-time monitoring. Requirement eight did provide methods of testing but these methods did not seem the safest for the human test subject. The device should be tested for high temperatures using lab equipment so no subject is burned.

It was noticed this group had a much smaller time period for device functionality (about 30 minutes). This requirement value should be increased. New level one requirements should be added that stress the body signals the group wishes to acquire based on the customer’s demands (similar to A-TeChToP’s Fall 2014 requirements). Then the level two demands could delve into the details. More research is required to determine whether the requirements’ verification tests could have utilized equations.

Spring 2016 New Requirements:

The second set of requirements have a large portion of the level one requirements integrated and thus the foundation of our requirements will be modeled after those. However, our new requirements will mention the signals A-TeChToP will acquire, similar to the level 1 requirements of the Fall 2014 A-TeChToP group. The Fall 2014 group does an excellent job of listing the requirements related to blood oxygen, temperature, heart activity, and body orientation. The group connects the measurements to diseases, which is important for the Customer’s expectations.

Each desirable overarching measurement will have a requirement. Since this is the Super A-TeChToP, new requirements concerning electrodermal activity and electrocardiograms will also be added.

These may include:

  1. The device shall accurately measure electrodermal activity such that the detection of grand mal seizures will match that of a traditional electroencephalogram [1].
  2. The device shall measure the QRS complex, P wave, and T wave of heart signals with high enough resolution to detect various types of arrhythmias [2].
  3. An alarm shall alert the parent and people nearby when one of the child’s biological signals has dropped into a dangerous range [3].

Past Budgets:

Spring 2015 Wednesday

From: http://arxterra.com/atechtop-final-documentation/ (Project Budgets)

Spring 2015 Friday

From: https://www.arxterra.com/verification-of-budget-requirements/ (Component Acquisition and Budget Data Sheet)

Spring 2016 Discussion and Preliminary Budget:

One group spent approximately $260, while the other spent approximately $160, which makes for a large price gap. For our preliminary budget, we will assume it takes $300 to implement the old sensor suite. Another $200 will be added for the electrocardiogram sensor and $200 more will be added for the electrodermal activity sensor. This results in a total preliminary budget of $700, which is $100 per member. The budget per person matches the preliminary budgets of the past. Past Schedules:

Past Schedules:

Spring 2015 Wednesday

From: http://arxterra.com/atechtop-final-documentation/ (Project Status)

Spring 2015 Friday

From: http://arxterra.com/atechtop-final-documentation-2/ (Project Completion Status)

Spring 2016 Discussion of Schedules:

The schedules suggest a small portion of the project should be completed each week in order to successfully meet all of the requirements. Because the current A-TeChToP group has such a large number of members, it will be important to schedule tasks in parallel, with one sub-group working on the new electrodermal device and the other working on the old sensors and electrocardiogram.

Spring 2016 Discussion of Videos:

The Spring 2015 Wednesday video (http://arxterra.com/atechtop-final-video/) had an overly dramatic introduction to the video that detracted from the device itself. The video would have been better if it had some sort of narration or subtitles that provided more information concerning the goals and outcomes.

The Spring 2015 Friday video (https://www.arxterra.com/atechtop-final-video-spring-2015/) thoroughly demonstrated the engineering method. However, it would have been better if the footage had been more realistic, as it was obviously scripted at the beginning.

In order to create a high quality video, it will be important to film small segments throughout the course of the project. It will also be important to determine which group member is a skilled editor.

Systems Engineer Research

Emphasis on Old Sensors

Omar Rojas (Systems Engineer)

Source Material

  1.             ATechTop Final Documentation, Project Requirements, Feb 4, 2016, http://arxterra.com/atechtop-final-documentation/
  2.             ATechTop Final Documentation, Prototyping/Simulations, Feb 4, 2016, http://arxterra.com/atechtop-final-documentation/
  3.             ATechTop Final Documentation, System Block Diagram, Feb 4, 2016, http://arxterra.com/atechtop-final-documentation/
  4.             ATEchTop Requirements: Level One and Two, Level Two, Feb 4, 2016, http://arxterra.com/atechtop-requirements-level-one-and-level-two/
  5.             ATECHTOP Final Documentation, ATECHTOP Project Requirements, Feb 4, 2016, https://www.arxterra.com/category/communites/members-and-communities/a-techtop/
  6.             ATECHTOP Final Documentation, System Design, Feb 4, 2016, https://www.arxterra.com/category/communites/members-and-communities/a-techtop/
  7.             ATECHTOP Project Requirements, Project Level 2 Requirements, Feb 4, 2016, http://arxterra.com/atechtop-project-requirements/


  1. Chi, Yu M., and Gert Cauwenberghs. “Wireless Non-contact EEG/ECG Electrodes for Body Sensor Networks.” 2010 International Conference on Body Sensor Networks (2010): n. pag. Web. 6 Feb. 2016.
  1. ADXL3 Accelerometer, Code, FEb 6, 2016, https://www.arduino.cc/en/Tutorial/ADXL3xx
  2. “LM34 Precision Fahrenheit Temperature Sensors.” Texas Instrumentation (n.d.): n. pag. Web. 6 Feb. 2016.
  1. “Pulse Sensor.” Sparkfun. N.p., n.d. Web. 07 Feb. 2016.

Review of Literature

Requirement Evaluation Rubric Number
1 2 3 4 5 6 7 8 9
1. Transmission of signals through Bluetooth to Android phone and from Android phone to Arxterra control center should have a minimal cumulative delay for immediate reaction time. Exact time TBD Y Y Y N Y N Y Y
2.  Maximum required range between sensor suite and phone will be the length of an average hospital room Y Y Y N Y N Y Y
3. Electrical components will be encased in a spray-on water resistant substance to qualify as level two water resistancy. Level two resistance “allows with water such as washing hands or light rain” Y Y Y Y Y N Y Y
4. ATechTop sleeve should be made out of a water repellent fabric N N Y Y Y N Y Y
5. Weight of device must reamin under 4lbs., since this is the maximum weight that an average five year old should carry Y Y Y Y Y N Y Y
6. The size of the ATechTop sleeve will not exceed 11 inches in length with a minimum diameter of 2.5 inches. This is the average length of 5 year old’s arm, so we cannot exceed these measurements. Y Y Y Y N N Y Y
7. Make-before-break battery pack should be incorporated in the design to allow constant monitoring without interrupting the 24 hour flow of signals Y N Y N Y N Y Y
8. Android phone and Bluetooth device will not exceed SAR regulation of 1.6W/kg as stated by the FCC Y N Y Y Y N Y Y
9. Device will not reach a temperature greater than 86°F, when people begin to feel the sensation of heat Y Y Y N Y N Y Y
10. In order for project to stay writing budget and meet deadline requirements, no purchase may be made for items outside of the United States Y Y Y N N N Y Y
11. Purchases cannot be made for sensors which need to be manufactured before shipping in order to meet deadline requirements. Y Y Y N N N Y Y
12. Sensor location for the ECG and pulse oximeter will be placed on each earlobe Y N N N Y N Y Y
13. Most common skin irritants caused by allergic reactions to materials include: latex, formaldehyde resins, exposed elastic, and dispersal dyes which include azo and anthraquinone structures. The wearable body network will reflect understanding of these common allergies by not including them in the design. Y Y Y Y Y N Y Y
14. The Arduino computing platform will be used because it possesses the needed capabilities to interact with the Arxterra website, students have experience working with Arduino devices, and also it has wearable properties. Y Y N N Y N Y Y
15. Electrocardiogram sensor must provide an accurate enough representation of a user’s signals such that an observer on the Arxterra website will be able to determine with 100% accuracy the difference between an individual’s physiological signals at rest and after physical strain Y Y Y N Y N Y Y
16. Bluetooth, IEEE 802.15.1 standard will be used as the wireless method of communication between the Arduino and Android phone due to its simplicity interacting with both the Android phone and the Arduino platform. Y Y Y N Y N Y Y
17. Batteries will be used to power the body network wirelessly for a period of at least 30.2 minutes at a time without needing recharge or replacement. Y Y Y N Y N Y Y
18. Programming for the project will be implemented in Arduino IDE for its ease of interaction with Arduino hardware. Y N N N Y N Y Y
19. In order for the project to stay within budget and meet deadline requirements, a shield for sensors to communicate with the Arduino will be custom-designed by group members. Y N N N Y N Y Y
20. Pulse, body temperature, and blood oxygen levels must be clearly presented and updated in real-time on the Arxterra website and mobile application. Y Y Y N Y N Y Y
21. An alert must be sent to the parent whenever vital sign measurements read as “unsafe” (as defined by settings in the Arxterra app). Y Y Y N Y N Y Y
22. Arxterra’s alert settings will be password protected. Only parent and physician will have altering access to Arxterra’s alert settings. Y N Y N Y N Y Y

Summary of Previous Second Level Requirements:

I reviewed the second level requirements that have been used by past groups. The requirements the previous groups have implemented in their design, for the most part are in the correct place. Requirements such as the maximum weight the device is allowed to hold, the required range at which the sensor suite and phone should be able to communicate, battery life, and safety precautions such as temperature are all valid and appropriate.  There were some requirements I felt belong in level 2 subsystem requirements. Requirements such as the sleeve being made out of water repellant fabric, battery design, and selecting the language in which to program the microcontroller. These requirements are too specific for systems engineers to dwell into and should be the responsibility of the control or manufacturing engineer.

Old Sensors:

LM34 (Temperature Sensor):

This chip has an accurate reading of +/- 1 °F which proves to be a reliable sensor to determine the temperature of the subject wearing our device.


This sensor is useful to help determine the percentage of oxygenated blood to deoxygenated blood by converting the light from alternating red and infrared LEDs to a frequency value that a correlation to the percentage value of the oxygen in the blood

Pulse Sensor:

This is a plug-and-play heart rate sensor to be use for Arduinos, which can be helpful to meeting deadlines and moving the progress of the project forward.

Lilypad Accelerometer ADXL335:

This accelerometer is one that is used in correlation with the LIlypad Arduino. If we choose to use a different Arduino, we will have to select a new accelerometer. My suggestion is the ADXL3xx which can be used with any Arduino board.


The sensors used in the past by other groups have been successful with their projects. With our iteration of the project, we have new ideas that would require us to look at different sensors. The temperature sensor used in the past, a LM34 chip, proves to be reliable according to the previous group’s documentation. The accelerometer will have to change since one of our new goals is to make the device smaller. The lilypad Arduino had an accelerometer integrated in it, and our group have had discussion of using a different Arduino model. Thus, a new accelerometer will be needed for our device. The pulse sensor and oximeter still have relevance with our project and more than likely will be incorporated in our design as well.

New Requirements:

Some additions I have is to include a requirements regarding the flexibility of the device. The device should be able to function without impairing the movement of the children wearing it.  Placement of the sensors, cable management of wired sensors, and the reliability of wireless sensors will have to be explored with other criteria to determine which one is the most optimal. There should be more consideration into “child-proofing” the device. The device should be able to handle the external forces, such as falling, that the child will put on the device. Some preventative measures for impacts should be incorporated into the design.

Emphasis on ECG

Robin Yancey (Systems Engineer)

Source Material

  1. ATECHTOP Project Requirements, Project Level 2 Requirements, 4-1-2015, http://arxterra.com/atechtop-project-requirements/
  2. ATechTop Requirements: Level One and Level Two, LEVEL 2, 4-6-2015, http://arxterra.com/atechtop-requirements-level-one-and-level-two/
  3. ATECHTOP Final Documentation, System Design, 4-1-2015, https://www.arxterra.com/category/communites/members-and-communities/a-techtop/
  4. ATECHTOP Final Documentation, Interface Definition, 5-10-2015, https://www.arxterra.com/atechtop-final-documentation/
  5. ATECHTOP Final Documentation, Electronics Design, 5-10-2015, https://www.arxterra.com/atechtop-final-documentation/
  6. ATECHTOP Final Documentation, Set-up and Initial Testing of Pulse Sensor Amped, Page 3, 4-20-2015, https://www.arxterra.com/category/communites/members-and-communities/a-techtop/page/3/
  7. ATECHTOP Final Documentation, Experimentation of Electrocardiogram Sensor, 5-16-2015, https://www.arxterra.com/category/communites/members-and-communities/a-techtop/page/3/
  8. ATECHTOP Final Documentation, Prototyping/Simulations, 5-10-2015, https://www.arxterra.com/atechtop-final-documentation/
  9. Testing and Modifying of the Heart Rate Sensor, 4-11-2015, http://arxterra.com/testing-and-modifying-heart-rate-monitor/
  10. Bioengineering Final Documentation- ATeChToP, 12-15-2014, https://www.arxterra.com/bioengineering-final-documentation-atechtop/

Works Cited:

  1. An-Bang Liu; Hsien-Tsai Wu; Cyuan-Cin Liu; Chun-Hsiang Hsu; Ding-Yuan Chen, “The factors influence compatibility of pulse-pulse intervals with R-R intervals,” in Engineering in Medicine and Biology Society (EMBC), 2013 35th Annual International Conference of the IEEE, vol., no., pp.2068-2071, 3-7 July 2013
  2. Pulse Sensor Amped Arduiano Code V1.2 Walkthrough. (2016) Retrieved from: http://pulsesensor.com/pages/pulse-sensor-amped-arduino-v1dot1
  3. ECG vs. PPG for Heart Rate Monitoring, Which is Best?. (2016) Retrieved from: http://neurosky.com/2015/01/ecg-vs-ppg-for-heart-rate-monitoring-which-is-best/
  4. Bharadwaj, A., Kamath, U. Techniques for Accurate ECG Signal Processing. (2011). Retrieved from: http://www.eetimes.com/document.asp?doc_id=1278571
  5. Graves, P. (2011). How to Read a Pulse Oximeter: Heart and Pulse Rate. Retrieved from: http://www.meditech.com.cn/Meditech-Library/Read-a-Pulse-Oximeter–Heart-and-Pulse-Rate
  6. Delano, Maggie K.; Sodini, Charles G., “A long-term wearable electrocardiogram measurement system,” in Body Sensor Networks (BSN), 2013 IEEE International Conference on , vol., no., pp.1-6, 6-9 May 2013
  7. What Does an Electrocardiogram Show? (2010). Retrieved from: https://www.nhlbi.nih.gov/health/health-topics/topics/ekg/show
  8. Sarkar, S.; Misra, S., “From Micro to Nano: The Evolution of Wireless Sensor-Based Health Care,” in Pulse, IEEE , vol.7, no.1, pp.21-25, Jan.-Feb. 2016
  9. Seok-Oh Yun; Moon-Keun Lee; Lee, K.G.; Jinsung Yi; Su Jeong Shin; MinHo Yang; Namho Bae; Tae Jae Lee; Jinho Ko; Seok Jae Lee, “An integrated and wearable healthcare-on-a-patch for wireless monitoring system,” in SENSORS, 2015 IEEE , vol., no., pp.1-4, 1-4 Nov. 2015
  10. Angel Sensor M1. (2015). Retrieved from: http://store.angelsensor.com/collections/frontpage/products/angel-sensor-m1
  11. Ramirez, E. Wrist Wearables: How Many Are There? (September 2014). http://quantifiedself.com/2014/09/wrist-wearables-now/
  12. What Is Arduino? (2016). Retrieved from: https://www.arduino.cc/en/Guide/Introduction
  13. Xudong Sun; Yue Zhang, “Design and Implementation of Portable ECG and Body Temperature Monitor,” in Computer, Consumer and Control (IS3C), 2014 International Symposium on, vol., no., pp.910-913, 10-12 June 2014
  14. Denton, E. (2015). Learn How to Measure Body Temperature Accurately and Cost Effectively [PowerPoint slides]. Retrieved from: http://www.ti.com/lit/ml/slyw051/slyw051.pdf
  15. Medical Temperature Sensors. (2013). Retrieved from: https://www.thermistor.com/medical-temperature-sensors
  16. NASA Systems Engineering Handbook Section 4.2 Technical Requirements Definition Start (page 40) and Appendix C page A: 279

Literature Review

Missions, Systems, and Test Review 1 of Past Axterra A-TeChToP Projects

This includes level 2 system requirements, block diagrams, and system electronic and software interface design (with a focus on topics relating to the ECG, as instructed by project manager.)

Level 2 Requirements Review:

The NASA Systems Engineering Handbook was used to help determine the quality of each of the past projects requirements [16]. Figure 1 shows a table listing the questions that should be answered “Yes” to define a useful requirement, and the whether the corresponding requirement seemed to follow these guidelines.


Figure 1. Systems Engineering Requirement Evaluation Questions

Since most of the answers in the graph are “No,” it is clear that the system engineers will need to greatly improve the requirements, this semester. Based on the level 1 requirements, there also many missing requirements, which need to be added to level 2 requirements.

Notes on specific requirements:

Requirement #1(Friday):

I don’t think this requirement is necessary, and could even move the design process backwards. If there are very good reasons for needing a part purchased outside of the United States, then there are ways of making sure that the part arrives on time, such as ordering the part way ahead of time. The cost of a part purchased outside of the U.S. would be equal to the total cost of purchasing the part in U.S. dollars, plus shipping costs. If this happens to fall within the budget requirements, then this could be a good purchase.

Requirement #2(Friday):

A form of this requirement may be helpful to because it would not be necessary or realistic/realizable to design and manufacture all of the sensors, ourselves, especially with limited time.

Requirement #3(Friday):

There is no reason why an ECG and pulse oximeter must be located on each earlobe, and it is actually not a good place to measure ECG. A better requirement may be to ensure that the ECG is located in the safest place on the child’s body, in which the heart activity can be accurately measured and ECG can be visualized (see New Requirements on ECG below). For the pulse oximeter, the earlobe location may be a good location to get an accurate signal (see below), but this is not indicated in the requirement.

Requirement #4(Friday):

This is a good requirement because it will be important to keep in mind the skin allergies and irritants.

Requirement #5(Friday):

If the group discovers that the Arduino microcontroller will be small enough and meets the needs of the design, then the requirement should be established. It is likely that it will be used because Arduino has some of the best hardware and software for building prototypes [11]. Otherwise, learning a new computing platform or programming language would not be as hard when students already know how to use Arduino.

Requirement #6(Friday):

It will be very beneficial to have a highly accurate ECG recording display because this body signal gives some of the most important information about a person’s health. A standard HR monitor may not help determine the cause of an increase in heart rate. ECG can be used to identify serious conditions such as fainting, seizures, severe electrolyte abnormalities, a pulmonary embolism, or cardiac arrhythmia. There are also a number of changes that take place in the ECG wave intervals, during exercise, and it may be helpful for the parent/care-taker to know how much and what type of physical activity the child is taking part in.

Requirement #8(Friday):

This should be removed because it is the same as the level 1 requirement #4, accept it is lacking the source. The average time allotted for children to play at school, may not be enough due to the fact that the child will probably go out to play for much longer times after school or on the weekends.

Requirement #9(Friday):

This is unnecessary because it is implied in requirement number 5.

Requirement #11(Friday):

This is in the level one requirements.

Requirement #12(Friday):

Alerts may be helpful.

Requirement #13(Friday):

This requirement is not directly linked to any level 1 requirement.

Notes on 2015 Level 2 System Requirements (Wednesday Group):

I agree with most of the Level two requirements put forth by the Wednesday group, but I would make changes to requirements number 4,5,6 and 7. The height and weight of the device should be required to be significantly lower than the maximum height and weight a child can carry, because it cannot bother the child while he or she is running or jumping either. A longer battery life may be possible, so requirement number 7 may not be restrictive enough. I think that requirement 4 should be removed since a shirt is not necessary for the device, and a source for number 9, should be added. I will do research in communication methods and delay times, to improve requirement number 1 to give quantitative information and sources. Requirement number 2 might need to allow for a slightly longer distance requirement, but this also needs research and sources.

Proposed New Level 2 Requirements (draft):

(According to IEEE Standards Style Manuel, shall is the word used to indicate a requirement, while should is a recommendation.)

In response to the Friday group’s level 1 requirement of “the ability to monitor blood oxygen levels, heart activity, temperature, and body orientation,” at least 4 requirements should be established with respect to the signal specifications and methods for each measurement:

1.A pulse oximeter shall measure how well oxygen is traveling to the lungs and heart.

– This device is chosen because it is non-invasive, safe, painless, and can be used for long durations [5].

    • The pulse oximeter shall be accurate enough that the pulse rate reading of the pulse oximeter matches the manual reading of the heart rate, which is between 60 and 120 for a child, with an SpO2 level between 96%-99% [5].
    • The pulse oximeter should be placed on a part of the body where light can shine through the blood flowing though.

– A pulse oximeter detects hemoglobin saturated with oxygen by emitting an infrared light through the skin tissue to a photosensor on the other side [5].

2. An electrocardiogram shall be implemented to measure heart activity.

– The electrical activity of the heart can show many more potential problems, than other devices, due to the fact that the visible waveforms change in distinct ways [7].

*See Summary of Proposed Subsystem Requirements for ECG below

3. Temperature should be measured with an IC temperature sensor or an NTC thermistor to ensure the most accurate reading of body temperature [13] [14] [15].

  1. The temperature reading from the implemented device shall measure 37 degrees Celsius on a normal, healthy human.

4. Body orientation should be measured both with an accelerometer and a gyroscope. (requirements will be made for the specifications after research)


If we decide to implement and EEG sensor, for seizures, the Neurosky device connects to the Arduino, the phone application, and Sparksfun board. This will have to be further researched.


Other New Requirements need to be added for the following:

  • communication method (eg. Bluetooth, Zigbee)
  • exercise/play test (eg. Should work while running for five minutes)
  • alerts when any of the signals are at a dangerous level
  • comfortable for the child

Block Diagrams:

For the most part, the block diagram is good because it shows how the sensors connect to the microcontroller, powered by a battery, to process signals, which are sent by Bluetooth to the hardware and software, for the user. We will need to make some changes, such as adding more sensor blocks.

Interface Definition & Design:

The interface definition and Fritzing Diagram helps explain all of the connections that were made to put it together.

Today, there are wearable/wireless wrist bands with the pulse oximeter, temperature, accelerometer, and gyroscope sensors, which display signals on the phone application and computer software via Bluetooth [11] [8]. Certain ones can even be purchased for around $100, and are open to researchers to program [10]. Unlike these four sensors, it is very hard to find any commercially available wireless and durable ECG sensors, so the development of this type of an ECG monitor is an interesting topic.

The Pulse Sensor Amped device was used to measure heart activity by the both of the A-TeChToP Spring 2015 semester groups. Although, in the Friday group’s final documentation, regarding this device, it was labeled “Experimentation of Electrocardiogram Sensor,” it actually uses a PPG to measure heart activity, rather than, measuring an ECG. In Spring 2015, AtechTop’s Friday group’s final documentation in “Set-up and Initial Testing of Pulse Sensor Amped,” also listed that the processing software provides a “display of the ECG signal graphically,” and showed a picture of a PPG. They also specified that the “Pulse Sensor Amped can retrieve an ECG signal with one electrode on the fingertip or earlobe, rather than using multiple electrodes to the body,” when it actually uses LED’s rather than electrodes. As indicated in The Pulse Sensor Amped Arduino Code Walkthrough on the device website, the Pulse Sensor Amped makes a photoplethysomograph, which responds to relative changes in light intensity, so that the signal goes up and down with changes in light intensity. (The schematic of Pulse Sensor Amped, shows the LED and amplifier circuit.)

A PPG (or photoplethysmogram), is an optically obtained plethysmogram or volume measurement, obtained by using a pulse oximeter which illuminates the skin and measures changes in light absorption, so that it can sense the rate of blood flow controlled by the heart’s pumping action [1][2][3]. On the other hand, an ECG uses electrodes to measure electrical changes in the skin, which come from the heart muscle depolarization during each expansion and contraction of heart chambers. This results in two very different signal waveforms [1].

The group also used the Pulse Sensor Amped to measure the heart rate. The pulse sensor code for the Arduino measures the IBI by timing between moments when the signal crosses 50% of the wave amplitude during the fast upward rise, and taking the average of the previous IBI times [2]. For our project we must decide whether the PPG or ECG is better for measuring heart rate. The PPG from the pulse sensor may be hard to detect on certain parts of the body, cold hands, or with poor circulation, as specified in the “Pulse Sensor Getting Started Guide” [2]. On the other hand, the ECG is a standard signal used for monitoring cardio health and wellness by healthcare providers and is better for measuring HRV because PPG peak interval accuracy is limited by the high power consumption of the LED’s, leading to need for a lower sampling rate [3]. PPG data can only be obtained from body parts with a high concentration of blood vessels, and can easily be distorted by effects of ambient light, different skin colors, and motion artifacts [3]. Taking into account size, power consumption, ease of use, and accuracy of output data, the ECG has a large advantage over the PPG [3].

A-TeChToP began in Fall 2014, and their design included the ECG in the block diagram, and indicated the choice of ECG sensor which would be used, but very little other information about it was provided. In all of their documentation, no final result verification of the sensor working or not working was included, and it does not show how the sensor was integrated into the overall design (or show any final design). The only information given regarding the ECG is that they planned to use the PS25205Bb Dry Sensor, and convert the analog output to digital using the ATMEGA32U4, using a USB cable. Since this must not have worked, better methods will be investigated, first.

The Wednesday group noted that they attempted to produce an ECG display, but it failed, so they had to result to the Pulse Sensor Amped, to just monitor heart rate. Luckily, they have indicated the reasons that the ECG device that they put together was unsuccessful, so it will be helpful to find solutions to each of these issues, in order for our group to successfully implement the ECG, this semester.

The three main problems they specified were the cables, the electrodes, and the capabilities of the board. The first issue they came across was that the cables produced noise in the signal whenever the person moved. Next, they found that the accuracy of the signal was dependent upon the type of electrodes used. They then found that they were not able to produce a proper graph programming the Sparksfun board.

Summary of Proposed Subsystem Requirements Regarding ECG:

In order to effectively obtain the ECG, the device needs to amplify and filter the signal so that it can be displayed to the user. It has a low frequency content, and a bandwidth between about 0.01 and 150 Hz is typical for diagnostic purposes, so a target for the signal quality should be at least 0.5 to 100 Hz [6] [4]. The signal is very small and only has a magnitude of a few millivolts, so it must be amplified with a minimum gain between 100 to 1000 V/V, and input referred noise less than 30 microvolts to be much smaller than the P wave. This also means, the ADC resolution should be 8-12 bits, and the waveform should be sampled by software at at least 250 samples per second. The device must be discrete, and it will be worn for long periods of time, while undergoing a lot movement, so the minimum number of leads and electrodes must be used. For example, use of one lead placed around the cardiac axis, and 2-3 electrodes in the proper locations will still be able to transmit a good signal [6]. Two electrodes and a single lead are required to take the potential, while a third electrode may be used as a reference to set a common potential [6]. Artifacts that could corrupt the ECG signal include the power-line interface, movement, breathing waves, electrode contact noise, and muscle contractions [4]. An instrumentation amplifier with a high CMRR such as 100dB will help remove common mode noise [4]. Updates on how the ECG subsystem will be implemented will be posted soon.

Emphasis on EEG

Rose Leidenfrost (Systems Engineer)

Source Material

  1. ATECHTOP Project Requirements, February 2, 2016, arxterra.com/atechtop-project-requirements
  2. Bioengineering Final Documentation- ATeChToP, Project Requirements, February 2, 2016, arxterra.com/bioengineering-final-documentation-atechtop/
  3. Journal of Medical Signals and Sensors, Detection of Epileptic Seizure Using Wireless Sensor Networks, February 2, 2016, www.ncbi.nlm.nih.gov/pmc/articles/PMC3788195/#!po=26.4706
  4. KidsHealth from Nemours, EEG(Electroencephalogram), February 5, 2016, kidshealth.org/parent/general/sick/eeg.html
  5. ATECHTOP Project Requirements, February 2, 2016, arxterra.com/atechtop-project-requirements
  6. ATeChToP Wednesday, ATechTop Requirements: Level One and Level Two, February 2, 2016, arxterra.com/atechtop-requirements-level-one-and-level-two/
  7. Bioengineering Final Documentation- ATeChToP, Project Requirements, February 2, 2016, arxterra.com/bioengineering-final-documentation-atechtop/
  8. Institute of Education Sciences, Average length of school year and average length of school day, by selected characteristics, February 2, 2016, https://nces.ed.gov/surveys/pss/tables/table_2004_06.asp

Literature Review

Analysis of past level 2 requirements:



Discussion: Most of the requirements analyzed above were well written and have a substantial significance to the project. Only a few had some minor issues, namely the requirement involving the battery pack and the requirement which discusses the waterproof sleeve. The requirement for the battery pack would be much better written as a requirement that the transmission of signal must not be interrupted by changing a battery. The sleeve requirement would be more quantifiable if it referred to the general housing of the device, not specific to that particular implementation with the shirt.

Block Diagram from Fall 2014


Discussion: The block diagram featured in the link above does a great job at laying out the overall connections to be made by the design. From the sensors, to microcontrollers then ultimately the Arxterra platform, each connection is clearly defined in this block diagram. As it applies to our forthcoming design, sensors will be added and adjusted accordingly. The block diagram also shows the usage of an arduino lilypad alongside an arduino uno which will be altered in our design.

EEG Research as it applies to Seizure detection:

An EEG is performed to measure the electrical activity of the brain. This measurement allows doctors to detect abnormalities in brain wave patterns which may be caused by disease. Epilepsy is one of the main neurological diseases that can be studied using EEG. During an EEG, electrodes must be placed on the scalp of the patient to obtain proper readings of the electrical signals of the brain.  

Alternately, a seizure detection system is proposed in the Journal of Medical Signals and Sensors using 3 wireless 2D accelerometers which are placed on the patient. An algorithm is developed based on patient data that would help detect the motor signs associated with the patient when a seizure is taking place and alert hospital staff or a close relative.

  • Sensor used is the MICAz mote wireless measurement system
  • Analysis is performed by an Artificial Neural Network and K Nearest-Neighbor

Due to the intrusive nature of the EEG electrodes, the ATeChToP team will proceed with seizure detection using alternate methods, i.e. accelerometers, electrodermal sensors.

ATeChToP Proposed Level 2 requirements:

Level 2 requirements being defined as the requirements which directly pertain to project specifics. These requirements are necessary as a means of fulfilling needs of the customer derived from the proposed level 1 requirements. Level 2 requirements must be a product of the higher level requirements and be of a quantifiable, realizable form.

Quantitative definition:

Design a noninvasive patient monitoring system that implement wireless monitoring through the Arxterra control panel. The monitoring system will provide a minimum of 5 vital signs to the nurse/caregiver to ensure that the child’s vital signs are not adversely affected by the physical strain of playing on a playground. The system will be capable of proper function in a playground environment and non-restrictive to the child’s play routine.

Proposed level 2 requirements:

  • Vital signs must be readily available for viewing on the Arxterra platform with minimum transmission delay.
    • Verification: Compare to transmission delay of previous designs.  
  • Design will allow for a range of 20 feet between the child wearing the device and parent/care provider.
    • Verification: Test operation at the 20 feet range between child and receiver.
  • Individual electrical components will be resistant to light water contact and moisture from playground environment.
    • Verification: Test operation when the device is exposed to a moderately damp environment.
  • Housing of components and sensors will be resistant to light water contact and moisture from playground environment.
    • Verification: Test operation when the device is exposed to a moderately damp environment.
  • Design will not use any materials which are known to be common allergens which may irritate skin.
    • Verification: All components included as part of the design are not made of common allergens.
  • Design will be implemented with a maximum weight of 1 pound.
    • Verification: The final design will be weighed.
  • Design will be an appropriate size for children 5 -13 years old.
    • Verification: Test the design on multiple children at each end of the age spectrum.
  • Design will be comfortable to the child not restricting their play.
    • Verification: Monitor the child at play using the device. Receive feedback from the child regarding his/her ability to play normally.
  • Design will minimize the appearance of the sensor suite.
    • Verification: Other children at the playground will be surveyed regarding the device.
  • Device will have a battery capable of monitoring the child for at least 7 hours, without a recharge.
    • Verification: Device will be tested for a minimum 7 hours of normal operation.
  • Device will meet FCC regulation for specific absorption rate.
    • Verification: The rate of radio frequency energy absorption of the device will be measured and compared to the FCC safety guidelines.
  • Project will be completed by May 4, 2016.
    • Verification: The device will undergo final operational testing by class time, Wednesday, May 4, 2016.
  • Project will be accomplished within budget.
    • Verification: Cost of completed project will be within $$$.

Electronics Engineer Research

Emphasis on Old Sensors and ECG

Stephen Cortez (Electronics Engineer)

Source Material



Literature Review

Level 2 Sub-Requirements: (Based upon original level 2 requirements):

  • ECG Location:
    • Must be conveniently placed and fully functional, providing a clear and different ECG signals for relaxed and strained readings. Potential locations include but are not limited to within the pit of an arm, a wireless wrist strap, and a comfortable chest piece direct connections.
  • Arduino platform must be used for communication between the sensors and the Arxterra website:
    • Arduino programming is intended to be used, however, rather than a Lilypad an Arduino mini pro will most likely be used due to its sufficient computing capabilities, number of pins, and compact size.
  • An alert must be sent to the monitoring party of the device whenever a sensor’s data is read as “unsafe” as defined by the group:
    • Not only is it intended for the monitoring party to be notified of potential dangers, it is being considered for the proper authorities and health services to be alerted of the danger as well as the location of the device that is attached to the child.
  • The length and diameter of the device should not exceed the average respective measurements of a five year old child:
    • The device sleeve should be made out of some sort of elastic material for a one-size-fits-all effect. This idea is under contemplation but the material has not been decided upon by the group.
  • Water resistance is greatly encouraged for this device up to a certain degree of moisture. This means that the device should retain function after being exposed to shallow amounts of water and rain:
    • The design of the device should accommodate water resistant features and/or the ability to be coated in water resistant spray. The success of this will be tested by coating a small dummy version of the device made from expendable parts with water resistance and then submerging it in distilled as well as tap water. The device will also be exposed to splashes of water in order to simulate rain drops.
  • A Bluetooth device must be used in order to transmit the information from the Arduino to the Arxterra software, which will require the use of an effective Bluetooth module with strong signal quality and range:
    • Some potential Bluetooth modules to consider are the BlueSMiRF (has Gold and Silver versions, Silver should be just fine, $34.95), the Bluetooth Mate (Gold and Silver) which was made specifically to work with Arduino Pro Mini ($24.95), and the BLE Mate 2 (which is Arduino Pro Mini compatible and uses low energy consumption, $29.95). A cheaper option is the Simblee BLE Module, which is $19.95 and is Arduino compatible, uses low power, and can be programmed with a display to connect to a smartphone device.

Device Recommendations:

  •  ECG Placement:
    • The ECG device should be placed with one node in the upper/inner area of the child’s arm and the other node around the bicep. This method of ECG measurement is possible and provides a smaller setup of electrodes. If this design is not considered, it is also possible to design wrist electrodes (similar to the FitBit) in order to wirelessly monitor ECG signals.
  • Arduino MCU:
    • The Arduino Mini Pro is the current desired model for this product. The Mini has the computational capabilities for this project as well as a small size which is preferred. If the Arduino Mini Pro is not chosen then the default Lilypad MCU will most likely be used due to its size. Priced at $9.95.
  • Bluetooth Communication Device:
    • The Simblee BLE Module is recommended since it is a low power consumption and is compatible, although not made for, with the Arduino Mini Pro. The price is also the lowest and the size appears to be ideal.
  • Motion Processing Unit (MPU):
    • Previously, an accelerometer on the Lilypad MCU unit was used (ADXL335 accelerometer). Recommended to now use either a MPU6050 or MPU9150 since both utilize the same Arduino libraries, both have code already written and large forums. Also, some group members have previous experience with these particular sensors.

Emphasis on Old Sensors and EEG

Marena William (Electronics Engineer)

Source Material

[1] Arxterra Website, Power Supply Selection


[2] Healthline Website, Common Triggers for Partial Onset Seizures.


[3] Wikipedia, Electroencephalography.


Literature Review

Level Two Requirements:

-Maximum required range between sensor suite and phone will be the length of an average hospital room.

Verification: Child wearing device will be asked to stand desired distance away from Android phone with signals being continuously transmitted.

Comment: No average hospital room was referenced and the signal transmission distance between the sensor suite and the phone was not specified. The range suggests whether the child could have the phone in their backpack in a situation like a classroom.

– Electrical components will be encased in a spray-on water resistant substance to qualify as level two water resistancy. Level two resistance “allows for contact with water such as washing hands or light rain”.


Verification: Water Resistant Coating Test will be conducted. Partially submerge item in distilled water, evaluate for loss of function.


Comment: Test result was not included in verifications.

ECG Device Selection:

The previous group (Spring 2015) chose to use a Sparkfun Heart Rate Monitor over the Plessey Dry Surface ECG to fulfill the water-resistivity requirement for the sensor suit. In the case of designing a fully waterproof suit that protect all the sensors, the Plessey Dry Surface could be used as it shows more accuracy and less noise for the signal.  

Temperature Sensor:

The temperature resistor used in the past semester ATechTop was a regular LM34 that is not waterproof. In the seek of designing a water-resistance/ waterproof ATechTop, DS18B20 could be used instead of the LM34. The temperature sensor DS18B20 also provides a good range (-55 to +125 ℃) which fulfill the requirements.

Pulse Oximeter:

According to the previous team (Spring 2015) the Pulse Oximeter circuit that was built from scratch works very well and help in keeping the product under the budget as manufactured ones are costly and perform the same.

Power Supply, Batteries and Voltage Regulations:

The LiFePO4 chose by the previous project makes perfect match for the requirements. One of the main advantages is that the  LiFePO4 is chargeable making the product more efficient. The search for a better battery is still in progress to find a smaller enough to be wearable yet have enough power to run the sensor suit longer. On the other hand, the Arduino board output supplies 40mA at 3.3V which is not enough to run all the sensors as discovered by the last years’ ATechTop group. The path chosen by the group is the best so far by directly connecting the LM350 voltage regulator which drops the 6.4V input voltage from the battery to 3.3V. A separate conjunction is to be made from the power supply(LiFePO4 battery) directly to the Arduino Uno before running through the voltage regulator in order for a voltage greater than 5V to run the microcontroller. More details could be found at the trade-off study done by the previous ATechTop project [1]

New Research Ideas:

Upon the interest of the company President and the Customer, a new sensor that would determine whether the child is having a seizure, possibly EEG,  need to be to the existing sensor suit. Below are few results about the EEG sensors: background about seizures and the EEG sensor, different kinds of EEG sensors, and advantages and disadvantages.

A seizure is caused by abnormal electrical activity in the brain. When a seizure occurs, a child may experience a variety of symptoms such as losing consciousness, experiencing uncontrollable muscle movement, losing awareness, or experiencing sensory perception changes. If the child has more than one seizure, he could be diagnosed with epilepsy. Epilepsy is a neurological disorder that causes chronic seizures. Electroencephalography (EEG) is an electrophysiological monitoring method to record electrical activity of the brain and is most often used to diagnose epilepsy, which causes abnormalities in EEG readings.[2]

There are different EEG sensor types, each differ in the method the measurements are made. In Sequential Montage each channel (waveform) represents the voltage difference between two adjacent electrodes and the entire montage consists of a series of these channels. In Referential montage each channel represents the difference between a certain electrode and a designated reference electrode. Another popular reference is “linked ears,” which is a physical or mathematical average of electrodes attached to both earlobes or mastoids[3]. This particular method could be combined with the existing Pulse Oximeter sensor to measure two different readings at the same location and also avoid having the child wear electoreds on their head in a bulky look.

The advantages of EEG are so many, here are some of them. Hardware costs are significantly lower than those of most other techniques, EEG sensors can be used in more places than fMRI, MRS, or MEG. EEG has very high temporal resolution, on the order of milliseconds rather than seconds. EEG is relatively tolerant of subject movement, unlike most other neuroimaging techniques, and there even exist methods for minimizing and eliminating movement artifacts in EEG data. On the other side, the main disadvantage of the EEG is that it poorly measures neural activity that occurs below the upper layers of the brain (the cortex). Also, sometimes the measurement takes longer as location on the scalp(body) varies.

Manufacturing Engineer Research

Mimy Ho (Manufacturing Engineer)

Source Material

Anura Fernano. “Safety is an essential concern for the future of wearables”. http://betanews.com/2015/05/11/safety-is-an-essential-concern-for-the-future-of-wearables

ATeChToP Project Requirement February 9, 2016, arxterra.com/atechtop-project-requirements 

Development of Printed Circuit Board. February 9, 2015 https://www.arxterra.com/development-of-a-printed-circuit-board/

“Flex PCB – (FPCB)”. https://www.sfcircuits.com/pcb-production-capabilities/flex-pcbs

Making Your Printed Circuit Board (PCB) as Small as Possible. http://predictabledesigns.com/making-your-printed-circuit-board-as-small-as-possible/

“Safety Facts on Scald Burns” http://www.burnfoundation.org/programs/resource.cfm?c=1&a=3

Why multilayer pcb is used so widely? http://www.goldphoenixpcb.com/html/Support_Resource/others/arc_110.html

Literature Review

Propose Level 2 requirement:

The wearable device’s material will not cause a child any skin reaction.

  • Verification: The requirement will be clarify by keep track all the document related to the material.
  • Discussion: The ATeChToP Friday used the strap that is used for backpack strap, which won’t cause any skin reaction because the strap is worn outside clothes. There are no direct interaction with skin at all.
  • Verification: Testing materials compliance https://www.arxterra.com/verification-testing-materials-compliance/

Any heat generated by the device should be below  100º F/39º C

  • Verification: The device will be worn and monitor continuous for 4 hours to see if any harm associated with the heat elevated through use.
  • Discussion: The ATeChToP Friday team had a requirement that the heat of device should be below 45° Celsius (113° Fahrenheit), which cannot be apply for a child’s device because a child’s skin got burn quickly than an adult.

The PCB board needs to be order by the second week of April this semester.

  • Verification: By the end of the April will have the PCB.
  • Discussion: The PCB took 12 days to manufacture and shipped for the Friday team. They used one layer PCB board to matching the size with the Arduino LilyPad. And the Wednesday team did the home made PCB because they did not have enough time to order the PCB from the website. I suggests that the electronics team will send the schematic on time so I can have enough time to design the board layout on the EagleCAD and order it online.


  • I suggest using multi layers PCB to reduce the size of the PCB as a dime as Customer and President’s request.  Based on the article “Why multilayer pcb is used so widely? “, the benefit of using multilayer PCB is to perform multi-function, high capacity and small size.
  • Another possibility if the design looks like a watch, a flex PCB can be used. The advantages of a flex PCB:  Reduced wiring errors, elimination of mechanical connectors, unparalleled design flexibility, higher circuit density, stronger signal quality, improved reliability and impedance control, size and weight reduction. On the other hand, the flex PCB disadvantages also exist, including the following: low temperature ability in flex circuits, more difficult & complex assembly, easily damaged through improper handling (easy to bend and dent), sensitive to scratching, difficult or impossible to repair once damaged, requires proper storage conditions (sulfur free plastic)