The device is composed of an amplifier/filter and a microprocessor unit, everything surrounded by a metallic box to avoid interferences.
Safety warning: DO NEVER use devices like this with a regular computer, as it is not isolated from the electrical power network. It may kill you in case of an electrical anomaly!
Information about the authors: we are students living in Portugal and we developed this device for our school project named Palpita-me! (Beat in me!, says the heart). With our project we intend to alert the school community and the general public to the importance of the prevention of cardiovascular diseases. We are studying issues such as the circulatory system, its anatomy, physiology and measurable parameters, relevant diagnostic techniques (especially electrocardiography), hospital services and emergency, telemedicine, statistics and risk factors.
Take good care of your heart so that it will beat inside you for many happy years to come!
Feel free to visit our website and leave us a comment. We'd love hearing from you!
Step 1: Plans, Schematics and Board Layout
The microprocessor unit was made by a member of our team some years ago and at its core lies a PIC microcontroller.
To plot data on a laptop screen, we needed software that could simulate an oscilloscope. For that we used the excellent (and free) Oscilloscope.dll, written by Michael Bernstein. We thank him for his kind support.
Furthermore, we also prepared a list of components that is just too big to show up here. From our website, you can download this list, every schematic and layout we've made.
Step 2: Getting Ready for the Build
Regarding equipment, we used:
- Pneumatic solder paste dispenser, activated by foot pedal;
- Vacuum pipette pick-and-place unit;
- Soldering iron and its support;
- Miscellaneous workshop tools, like tweezers, pliers and so forth.
We ordered the bare board from a local electronics store and the rest of the materials (components) from Farnell.
We advise the usage of an anti-static wrist strap and the help of a friend.
Step 3: Applying Solder
For that, we used our semi-automated solder paste dispenser, but you could also do it by hand carefully operating the syringe.
Step 4: Placing the Components
In case you don't possess specialized equipment, use the tweezers and take your time.
Step 5: Melting the Solder
We used a simple kitchen hot plate to get 200º C or 392º F. The board heats up gradually until the solder paste gets shiny as we know it from finished boards.
After removal and cooling down, we soldered via wires on some holes and the input and output cabling for the preliminary testing.
Step 6: Tests and Troubleshooting
Even using the filter and a protecting metal box, due to the high amplifier gain we should operate our ECG apparatus away from cables, computers, projectors, etc.
Step 7: Boxing and Final Touches
Then, we placed stickers made by ourselves to show which plug is which.
Our device is now ready to roll!
Step 8: Demonstration
Below, we show a video demonstrating the operation of our ECG device:
Thanks for reading and have fun with ECG on your laptop! Again, feel free to visit our website and leave us a comment. We'd love hearing from you!