TDS (Total Dissolved Solids) Water Quality meter Interfacing
with Arduino, Node MCU, ESP32
Total Dissolved Solids (TDS) is a measure of the combined content of all contaminants contained in drinking water. A standard definition for “dissolved solids” is that they must be small enough to pass through a 2 micron filter. Contaminants larger than 2 microns are often referred to as Total Suspended Solids.
Total Dissolved Solids are classified by the EPA as a Secondary Contaminant. As a whole, they are considered more of a nuisance than a threat. Certain individual water contaminants that contribute to the Total Dissolved level, however, may pose long term health risks if they exceed certain levels.
Where Do Total Dissolved Solids Come From?
As water travels over the surface of the land or through the ground, it dissolves naturally occurring minerals and, in some cases, radioactive material. Water can also pick up substances from animals or human activity like industry and agriculture.
A TDS meter indicates the total dissolved solids like salts, minerals, and metals, in a solution. This parameter can be used to give you an idea of water quality and compare water from different sources. As the number of dissolved solids in the water increases, the conductivity of the water increases, and that allow us to calculate the total dissolved solids in ppm (mg/L).
Although this is a good indicator to monitor the quality of the water, note that it does not measure contaminants in the water. Thus, you can’t rely solely on this indicator to determine if the water is good for consumption or not.
What Treatment Systems Remove Total Dissolved Solids?
Reverse Osmosis (RO) remove TDS by forcing the water, under pressure, through a synthetic membrane. The membrane contains microscopic pores which will allow only molecules smaller than 0.0001 micron to pass through. Since the molecules of dissolved metals and salts are large compared to the water molecules, the water will squeeze through the membrane leaving the metals and salts behind. A professional Reverse Osmosis system is capable of removing 90-99% of the dissolved mineral salts from water. A pre-filter is usually required to protect the membrane and remove organics.
Input Voltage: DC 3.3 ~ 5.5V
Output Voltage: 0 ~ 2.3V
Working Current: 3 ~ 6mA
TDS Measurement Range: 0 ~ 1000ppm
TDS Measurement Accuracy: ± 10% F.S. (25 ℃)
Module Interface: XH2.54-3P
Electrode Interface: XH2.54-2P
Typical Connections of the ADS1115
The principle I2C connections for the ADS1115 is shown in the image below.
TDS Probe:
Number of Needle: 2
Total Length: 60cm
Connection Interface: XH2.54-2P
Color: White
The Sensor board has 2 pins on one side to which probe needs to be connected.
TDS (Total Dissolved Solids) Water Quality meter Interfacing with Arduino:
The sensor has three pins of which two pins VCC and GND shall be connected to 5 volts DC and ground of Arduino. Then there is output voltage available from sensor which shall be connected to Analog Pin A0 of Arduino board which will compute the total dissolved solids and express on LCD display as ppm. Then there are three Arduino pins viz., Pin 2 connected to Green LED, Pin 3 connected to Red LED, Pin 4 connected to Buzzer. Green LED indicates the Arduino powered on, Red LED and Buzzer switches on whenever the TDS is more than certain set value.
TDS (Total Dissolved Solids) Water Quality meter Interfacing with Node MCU:
The sensor has three pins of which two pins VCC and GND shall be connected to 3.3 volts DC and ground of Node MCU. Then there is output voltage available from sensor which shall be connected to Analog Pin ADC0 of Node MCU board which will compute the total dissolved solids and express on LCD display as ppm. Then there are three Node MCU pins viz., Pin GPIO2 connected to Green LED, Pin GPIO3 connected to Red LED, Pin GPIO4 connected to Buzzer. Green LED indicates the Node MCU powered on, Red LED and Buzzer switches on whenever the TDS is more than certain set value.
TDS (Total Dissolved Solids) Water Quality meter Interfacing with ESP32:
The sensor has three pins of which two pins VCC and GND shall be connected to 3.3 volts DC and ground of ESP32. Then there is output voltage available from sensor which shall be connected to Analog Pin ADC0 of ESP32 board which will compute the total dissolved solids and express on LCD display as ppm. Then there are three ESP32 pins viz., Pin GPIO2 connected to Green LED, Pin GPIO3 connected to Red LED, Pin GPIO4 connected to Buzzer. Green LED indicates the ESP32 powered on, Red LED and Buzzer switches on whenever the TDS is more than certain set value