By excluding the Smartphone and disposable parts (electrodes and batteries), the device whole
cost is between 20 and 25 Euros (25-30 US dollars).
Warnings and safety issues
This project is
NOT
a medical device and is not intended to be used as a medical device to
diagnose or treat any conditions.
The authors cannot be responsible for any harm caused by using any of the circuits or
procedures described on this manual. The authors do not claim any of the circuits or procedures
are safe. Use at your own risk. It is imperative that anyone who wants to build this device have
a good understanding of using electricity in a safe and controlled manner.
The ECG device is electrically connected to a person and only low voltage batteries must be
used for safety precautions and to prevent damage to the device.
DO NOT use any AC power supply, any transformer or any other voltage supply to avoid
serious injury and electrical shock to yourself or others. DO NOT connect any AC-line powered
instrumentation or device to the ECG device here proposed.
Placement of the electrodes on the body, provides an excellent path for current flow. When the
body is connected to any electronic device, you must be very careful since it can cause a serious
and even fatal electric shock.
Use ONLY battery (max voltage supply: 9V).
AD8232 uses a Right Leg Driver (RLD) to reduce common-mode interference. As specified in
the AD8232 component datasheet, “Note that when using this amplifier to drive an electrode,
there should be a resistor in series with the output to limit the current to be always less than
10uA even in fault conditions”. Off the shelf AD8232 modules usually uses a 360 kOhm
resistor in series with the RLD output since its supply is 3.3V. To power the Arduino Nano
board at least a 6V battery is needed (7V is the value recommended by Arduino), so to keep
the RLD current limit lower than 10 uA, a higher resistor is needed. See following paragraphs
for more details.
