ECG on Your Laptop

8/10/2019 ECG on Your Laptop

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http://www.instructables.com/id/ECG-on-your-laptop/

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ECG on your laptop!by JZweigeon April 23, 2010

Table of Contents

ECG on your laptop! ...........................................................................................................

Intro: ECG on your laptop! ....................................................................................................

Step 1: Plans, schematics and board layout .......................................................................................

Step 2: Getting ready for the build ..............................................................................................

Step 3: Applying solder ......................................................................................................

Step 4: Placing the components ...............................................................................................

Step 5: Melting the solder ....................................................................................................

Step 6: Tests and troubleshooting ..............................................................................................

Step 7: Boxing and final touches ...............................................................................................

Step 8: Demonstration .......................................................................................................

Related Instructables ........................................................................................................

Comments ................................................................................................................
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Author:JZweige Palpita-me!

I am the leader of the Palpita-me! project. And I love instructables!

Intro: ECG on your laptop!That's right! This Instructable shows you how to build a device that enables you to do an electrocardiogram on yourself, your family or your friends! All you need isintermediate-level knowledge on electronics, access to Ye' Ol' Electronics Shoppe (or online shopping if preferred) and a laptop.

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 aelectrical 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 heaWith 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 issuesuch as the circulatory system, its anatomy, physiology and measurable parameters, relevant diagnostic techniques (especially electrocardiography), hospital serviceand 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!

Image Notes1. A regular school laptop used for medical purposes! Image Notes1. Sometimes, scientists may become test subjects too. :D

Image Notes1. The Palpita-me! team together for some testing in the school's library.

Image Notes1. Main board: it has amplification and filtering functions2. Additional 50 Hz notch-filter3. Microprocessor unit4. Electrode inputs5. TO THE LAPTOP! :D6. NiMH 9V Battery
http://palpita-me.org/enhttp://palpita-me.org/enhttp://www.palpita-me.org/http://member/JZweige/http://member/JZweige/


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7. On/off switch

Step 1:Plans, schematics and board layoutOur ECG amplifier/filter board schematics is derived from an Analog Devicesapplication handbook. We adapted and complemented it to suit our needs and we usedPCB123 Schematicto draw the circuit schematics. Then, we used PCB123 Layoutto draw the actual board. PCB123 is a great program and it's entirely free, so you cget it here.

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 MichaeBernstein. 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'vmade.

Image Notes1. Our amplifier board as it's seen in PCB123 Layout 3D view.

Step 2:Getting ready for the buildIf you would like to reproduce the unit with minimum effort, we suggest you work in a properly equipped workshop, as you are going to deal with SMT (Surface MountTechnology).

Regarding equipment, we used:- Pneumatic solder paste dispenser, activated by foot pedal;- Vacuum pipette pick-and-place unit;- Soldering iron and its support;- Multimeter;- 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.
http://farnell.com/http://en.wikipedia.org/wiki/Surface-mount_technologyhttp://en.wikipedia.org/wiki/Surface-mount_technologyhttp://palpita-me.org/en/node/116http://palpita-me.org/en/node/116http://www.oscilloscope-lib.com/http://www.pcb123.com/


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Image Notes1. Multimeter2. Workshop tools3. Soldering iron4. Component boxes5. List of components6. Board schematics

Image Notes1. Wrist strap cable2. Solder paste dispenser

Step 3:Applying solderWhen you are ready to start assembling, the first step is to apply solder paste on the proper spots, that is, on the component solder lands.

For that, we used our semi-automated solder paste dispenser, but you could also do it by hand carefully operating the syringe.

Image Notes1. Applying solder paste

Image Notes1. Applying solder paste on the appropriate places.


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Image Notes1. Every drop of solder paste in its place? Check. Components? Check. It's timefor some component placing!

Step 4:Placing the componentsAgain with the help of our dispenser equipment, we used a vacuum pipette to suck the tiny components and to place them according to the layout of the board. It ismostly a work of patience and precision.

In case you don't possess specialized equipment, use the tweezers and take your time.

Image Notes1. Unpacking...

Image Notes1. Placing...


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Image Notes1. DONE!

Step 5:Melting the solderThe last main assembly step consists of applying heat to the board, so that the solder paste melts and establishes perfect contact between the board's copper pads anthe components' legs.

We used a simple kitchen hot plate to get 200 C or 392 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 troubleshootingAfter the assembly session, we ran tests and realized that our wave was suffering from 50 Hz noise originated by power conductors all around us. We then decided tobuild a small, passive 50 Hz notch-filter, as seen in one of the Intro pictures.

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.


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Image Notes1. Before applying the notch-filter... It is not that good, is it?

Image Notes1. After applying the filter... Beautiful!

Image Notes1. Amplifier/filter2. Microprocessor unit3. Additional 50 Hz notch-filter4. NiMH 9V Battery5. Our device while in test phase.

Step 7:Boxing and final touchesWe bought a metal box from our local electronics store and, with the help of an employee from our school, we managed to pierce it with the right holes for connectors,switches and so on.

Then, we placed stickers made by ourselves to show which plug is which.

Our device is now ready to roll!


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Image Notes1. The final product.

Image Notes1. Our device in action!2. Electrodes and clips kindly offered by Skintact.

Image Notes1. Electrodes2. On/off switch

Image Notes1. To laptop (RS232 connector)2. Charge the battery3. Auxiliary analog output for future development (rarely used)

Step 8:DemonstrationWe enjoyed very much this activity of our project. It was a way of applying technology to medical science and showing people their heart's electrical activity.

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!
http://palpita-me.org/enhttp://palpita-me.org/enhttp://www.instructables.com/id/ECG-on-your-laptop/step8/Demonstration/


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Image Notes1. Our project logo. Visit www.palpita-me.org

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Comments

2 comments Add Comment

MikBsays: May 8, 2010. 4:26 AM REP"DO NEVER use devices like this with a regular computer, as it is not isolated from the electrical power network."

Also do not interconnect the laptop with any *other* devices that are mains powered -- not the battery charger/power pack for the laptop, not toyour stereo, or to phone lines, broadband, internal wired networks, external antennas etc. All of these introduce possible paths for hazardcurrents to flow through you.

Real ECG machines are fully isolated to many thousands of volts, so there is no hazard. Toy ones are battery operated and stand-alone. There ia reason for this!

JZweigesays: May 8, 2010. 8:56 AM REPExactly! Excellent advice!
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