W19 Project development

From zero to one hundred

Introduction

Orientation for development

This is not a really assignment, it is a mountain view of the final project, the abstract for researchers, the executive summary for business. It shows  whole troubles and successes of the final project,

Summary

Q 1 by 1.

Answering questions

What tasks have been completed, and what tasks remain?

The idea

The goal it was to make 4 stages:
1) Capture ECG (Electrocardiogram). (From USA Fab ECG to EUROPE Fab ECG)
2) Process ECG. (from basic heart beat detection to Fast Fourier Transform)
3) Show visual result (from a basic LED to a Array LED) 
4) Design (goal is to make a case portable and good looking)

ITERATION 1. (Final Project) Completed!

Stage 1. Capture Electrocardiogram. Completed!

It was made the Fab ECG, and it works. The main problem is the noise reduction is for USA 60Hz power supply, so I will try in second iteration to create a new 50Hz Fab ECG for EU 50Hz power supply. 

After some tries with electrodes DIY, I can't make a good electrodes so I started to check commercial electrodes. It was very disappointing discover that most of commercial electrodes are bad and don't stick for more than 30 minutes on the skin. Just one commercial electrodes work ok. I'have made the cables, clip and adaptators.

Visit my final project PAGE 1 for further information

Stage 2. Heart Beat detection. Completed!

The analog signal from Fab ECG suffer a ADconvertion and a substraction. After that, if you make a chart of digital ECG, you will see that is possible to detect Heart Beat by threshold. I've designed the PCB and programmed the microcontroller.
Heart beat detection it works!

Visit my final project PAGE 2 for further information

Stage 3. Visual result. Completed!

For the first iteration, I tried just with one LED. It works!

Visit my final project PAGE 2 for further information

ITERATION 2. (Advanced)

Stage 1. Design the new 50Hz Fab ECG. Done... but it doesn't work. 
Remain debug

I've studied all Fab ECG components, designed the new 50Hz Fab ECG, studied how to make an active low pass filter for 50Hz, milled and soldering all components. But when I test it, I realize that some wire were missed. I tried to solve it with imaginative solutions, but it doesn't work. 
The best option is to redesign again the 50Hz Fab ECG with those missed wires and milled again. 

Visit my final projet PAGE 4 for further information

Stage 2. Fast fourier transform. Remain

I decided to keep pushing about analysis of ECG. I was studying how to make the FFT with 8bits microcontrollers. I discovered that the signal that you want to make the FFT have to be stationary and the ECG it is not stationary. In that case, you have to analyze a window where the signal is almost stationary. But chose one window or another one it is not easy, because have consecuences on FFT. After some deep research, I decided to give up. It's too deep for the short period of time that we have.

Visit my final project PAGE 1 for further information

Stage 3. LED array visual result. Complete!

The next step is to send messages with the LED array. I was experimenting about that point. After many problems with the LED array PCB, I got the possibility of writing words that move on the led array. I made word "NO" in a slide moving from right to left. About the stage 3 it is many more that I really could imagine to achive in those few weeks.

Visit my final project PAGE 5 for further information

Stage 4. Case Design. Complete!

Inside size was fixed by the battery size, the minimum size depens on the battery size.  One side of the outer case will be in contact with skin, so this part have to be ergonomic and soft. Inside the case, there are 3 departments, divided with 3 methacrylate layers. The departments are for: 1) Fab ECG, 2) Battery and 3) PCB2 Heart Beat Detector and PCB3: LED array. Complete!

Visit my final project PAGE 3 for further information

What has worked?

Electrocardiogram capture with 60Hz Fab ECG and commercial electrodes, Heart Beat detection with PCB2, Visual result with PCB3: Array LED, Slide word on Array LED, portable case and layers to store all PCBs.

What hasn't worked?

After finish my final project, I have tried to advanced a little bit more improving the visual result (done!) and improving the Electrocardiogram capture and processing data with 8 bit microcontroller. 

Finally, I hasn't worked 50Hz Fab ECG and Fast Fourier Transform on 8 bit microcontroller.

What questions need to be resolved?

I think, 50Hz Fab ECG is almost done. I have studied a lot how to make it and now I know how fix the missed wires. Could be very interesting for Fab Community a 50Hz Fab ECG.

About FFT for 8 bit microcontroller, Neil Gershenfeld told during my final project presentation that there are FFT libraries for 8 bit microcontroller. This is something to check and work.

What will happen when?

If those two questions are solved, we could capture the electrocardiogram without 50Hz power supply noise and we could work on frequency domain with ECG (that allow to work with Heart Rate Variability with all possibilities that it means).

What have you learned?

I'm Telecommunications Engineer and all my studies have been developed on "simulators", for me Fab Academy and specially my final project drive me to achive hands on level: Create my own design, 3D printing, molding and casting, and so on. About my final project, I have learned a lot of hands on electronics, and ergonomic design for wearables.