An Electrocardiograph is a piece of medical equipment used
to measure and record the voltages (ECG) produced as a result of heart muscle
By attaching electrodes (or ‘leads’ as they are known in the
trade) to the skin of your wrists, ankle or chest, our PC-Driven ECG project can
display, record or print out the same kind of ECG waveform on your personal
Why would you want to build one? Well, looking at the waveforms
generated by your heart can be both fun and educational.
The complete ECG setup using our new Electrocardiograph, a laptop PC (with USB) and home-made electrodes. You can also use commercial ECG pads.
You can monitor changes to your heart under various conditions,
as your heart is affected by many factors such as emotions, mental and physical
activity – even breathing.
All of these things have a demonstrable effect on the heart’s
ECG waveform. Being able to show this easily, safely and at low cost is an added
Professional ECG machines can cost anything from $4000 up, and
while this project is not intended to be used as a diagnostic device, the
displayed, recorded and printed waveforms are of a quality approaching that of
Our new PC-based electrocardiogram is smarter than previous
models because its operation is under the control of an inbuilt PIC
microcontroller. It’s also faster and compatible with modern PCs, because it’s
linked to the PC via a standard USB cable – thanks to the use of an Elexol
USBMOD3 interface module.
And finally it’s easier to use, because all functions are
controlled using a Windows-based GUI program, written in Visual Basic.
Both the PIC microcontroller’s firmware program and the Visual
Basic PC program will be available on the SILICON CHIP website
The PIC program (ECGSAMPL.HEX) is in hex code form ready for
PIC programming, while the VB program (ECGCONTR.ZIP) is in the form of a
zipped-up installation package. We imagine that kit suppliers will have already
programmed the PIC for you.
You’ll also need a special USB virtual COM port driver which
the PC needs to communicate with the ECG via a USB cable. This will also be
available on the SILICON CHIP website, as R9052154.ZIP.
Both the latter items can be installed directly on a PC running Win98SE or newer
USB-compatible operating systems. Note that it won’t work with Win NT-based
systems – not through any shortcoming in the design but the simple fact that NT
doesn’t recognise the USB port.
This project has not been designed for medical diagnosis. Correct interpretation of ECG waveforms and tracings is a complex and skilled procedure and requires medical training. The USB/ECG is presented here as an instructive and educational device only. If you are concerned about the health of your heart, consult your GP or a heart specialist.