1. How can I discharge my body?
2. I have also tried power bank, ...
- Ah, you body acts like an antenna (sort of radio set antenna) picking up the mains electromagnetic wave signal near by. It is different from static electric charge. In other words, you cannot "discharge" your body. You use the Einthoven Triangle connection of your single lead to cancel out the mains noise on your body. It is similar to the use of differential input or twisted pair wires to cancel out the noise. I recommend to read the two references below for more details.
- Yes, using power bank is good idea, because it is almost any noise free. I just use batteries, keeping it very near the AD8232, and decoupled anything with Rpi. (For MCP3008, you might also like to use batteries very near by.)
I don't use the 3.5mm plug and long wire. I keep the wires out to the AD8232 very short by directly connecting to the duPont male header.
You might like to look at the AD8232 ECG of my own faint heart. :)
Yes, noise is the most common ADC newbie sorrow.
The most trouble making noise comes from the 220/110 50/60Hz mains noise, which is picked up by the PSU, through EMI and through connecting and grounding wires.
In your ECG case, your little body is picking up huge mains noise, so you are in the biggest trouble.
On the other hand, the ADCs themselves also generate noise, though somewhat smaller, inside the chip, when they are doing high frequency chopping in analog to digital operation, and switching between analog and digital channels.
Before I move on, you might like to skim the posts referred at the bottom, where I discussed the noise problem using the very old SPI 10/12 bit MCP3x0y, ACS712/723, INA219/221, and how I have been trying to solve the problem using new type of low noise I2C/SPI 16/24 ADCs using HX711, ADS1025/1115, ADS1256, ...
You might notice that the new generation of ADCs almost always say their chip is very low noise, mains noise rejection, and selectable gain (to adjust the full scale for low resolution loss).
And if you are using MCP300x or MCP3204, do not use Vcc or resistor divided Vcc as the Vref, because Vcc is noisy. Use a good Vref chip such as KA431.
And it is a good idea to use a dedicated PSU, with adequate by pass caps, placed near the ADC. This way you can use this rather stable PSU as voltage reference, in case you do not want to use a zener or volt ref chip.
/ to continue, ...
Raspberry Pi Current & Voltage Sensors (10A rating and ~40V respectively)
Waveshare ADC Board negative value issue
ECG Realtime Noise Filtering (MCP3008, ADS1015/ADS1115) - Rpi Forum
Datasheets and Application Notes
ADC8232 Datasheet - Analog Devices
ADC Single-Lead, Heart Rate Monitor Front End - Analog Devices
Multiphysiological Parameter Patient Monitoring -Bill Crone Analog Devices
SparkFun AD8232 Single Lead Heart Rate Monitor Module - US$19.95
SparkFun AD8232 Single Lead Heart Rate Monitor Module Schematic
SparkFun AD8232 Single Lead Heart Rate Monitor Module Features
The AD8232 SparkFun Single Lead Heart Rate Monitor Board is used to
measure the electrical activity of the heart.
This electrical activity can be charted as ECG or output as an analog
ECGs can be extremely noisy, the AD8232 Single Lead Heart Rate Monitor
acts as an op amp to help obtain a clear signal from the PR and QT
The AD8232 is an integrated signal conditioning block for ECG and other
biopotential measurement applications. It is designed to extract,
amplify, and filter small biopotential signals in the presence of noisy
conditions, such as those created by motion or remote electrode placement.
The AD8232 Heart Rate Monitor breaks out nine connections from the IC that
you can solder pins, wires, or other connectors to.
SDN, LO+, LO-, OUTPUT, 3.3V, GND provide essential pins for operating
this monitor with an Arduino or other development board.
Also provided on this board are
RA (Right Arm), LA (Left Arm), and RL (Right Leg) pins
to attach and use your own custom sensors.
Additionally, there is an LED indicator light that will pulsate to
the rhythm of a heart beat, ...
ECG Signal Interpretation Learning Notes
Introduction to ECG Interpretation - FG Yanowitz 2018
How to use 1-lead ECG recorders to obtain 12-lead resting ECGs - JW Grier 2008
CJMCU-30100 MAX30102 MAX30100 Pulse Oximeter Heart Rate Sensor