LCD-LED DisplaySensors - Tranducers Circuits

DIY Water Quality Meter Using a Turbidity Sensor Schematic Circuit Diagram

Intro Of DIY Water Quality Meter

Just after the Kerala flood, I received requests from a few victims inquiring how to build a cheap device to ensure the quality of drinking water. For the purposes of water quality monitoring, I started the design of a simple Turbidity Meter capable of analyzing a water sample but without precision optics and electronics. Frankly, the given low-profile (yet expansible) design is good only for a rough qualitative analysis (not quantitative analysis) as it’s assumed that the community at present may not have fiscal resources to build costly devices and/or water quality analyzing may not be a sufficient priority to justify that expense!

The Backdrop

Turbidity is a universally accepted parameter for evaluating the quality of drinking water, and a Turbidity Meter is an optoelectronic device used to assess turbidity by measuring the scattering of light as it passes through a water sample containing colloidal particles that may harbor harmful microorganisms. Turbidity is typically expressed in units known as Nephelometric Turbidity Units (NTU) or the equivalent Formazin Nephelometric Unit (FNU). Nephelometry involves directing a light beam at a liquid sample and quantifying the intensity of light scattered at a 90° angle to the incident beam.

A Turbidity Meter typically comprises a single light source directed through a water sample, a chamber for containing the sample, and one or more photodetectors strategically positioned around the chamber. The common “single-beam” Turbidity Meter, as illustrated in the provided design pattern, primarily focuses on monitoring the light scattered by suspended particles within the water sample. It then produces an output voltage that is proportional to the turbidity or concentration of suspended solids.

DIY Water Quality Meter Using a Turbidity Sensor Schematic Circuit Diagram 1

Nonetheless, our Turbidity Meter utilizes an optical sender and optical receiver as the front-end sensor, functioning on the principle that the quantity of light passing through a water sample is contingent upon the concentration of suspended particles within the water. As the total suspended solids (TSS) level rises, the amount of light transmitted through the sample decreases. The remaining electronic components within the system circuitry subsequently gauge the transmitted light’s intensity to ascertain the turbidity of the sampled water. In essence, the Turbidity Meter simplifies the process by quantifying the light emitted by the sender and received by the receiver, ultimately calculating the water’s turbidity.

The Frontend

As you might have guessedthe front-end sensor is an optical device comprising an LED (light sender) and a phototransistor (light receiver). Because Turbidity Sensor modules are widely used in washing machines and dishwashers, you can buy a compact front-end sensor from most online electronics retailers. The TSD-10 Turbidity Sensor from GE (www.ge-mcs.com) and from Amphenol (www.amphenol-sensors.com) are compatible. Note that you can also see a maker’s version — the Gravity Arduino Turbidity Sensor from DFRobot (www.dfrobot.com) — everywhere on the web.

DIY Water Quality Meter Using a Turbidity Sensor Schematic Circuit Diagram 2

Here’s the schematic of the TSD-10 Turbidity Sensor’s (GE) inside electronics. TSD-10has a three-wire interface: VCC (+5 V) — GND (0 V) — OUT/SIGNAL (Analog V).

DIY Water Quality Meter Using a Turbidity Sensor Schematic Circuit Diagram 3

The Sensor Driver

The internal electronics of the turbidity sensor head ensures that it gives an analog output voltage in proportion to the level of turbidity. If the primary objective is to just detect when the water is turbid, then we can use a standard comparator circuit to switch an output load (a piezo sounder, for instance) when the turbidity reaches a pre-defined threshold value. Here’s a turbidity sensor driver circuit based on LM393 for the intended task. Tweak it!

DIY Water Quality Meter Using a Turbidity Sensor Schematic Circuit Diagram 4

On the Other Side

While I was experimenting with my old TSD-10 turbidity sensor lifted from a defunct washing machine, the ordered Gravity Arduino Turbidity Sensor from DFRobot arrived at my doorstep from an Indian online store a little sooner. Surprisingly enough, the sensor package consists of a sensor driver module in addition to the original sensor. The LMV358 IC-based module provides a three-pin interface to connect with Arduino (or any other microcontroller), and there is also an “analog/digital” selector switch on the module to flip between analog and digital output mode. The official DFR documentation (https://www.dfrobot.com/wiki/index.php/Turbidity_sensor_SKU:_SEN0189) states that in analog mode, the output value decreases at high turbidity, while in digital mode, the output pin goes high if the turbidity reaches the threshold value set by its on-board trimpot.

DIY Water Quality Meter Using a Turbidity Sensor Schematic Circuit Diagram 5

From the same source, I got this graph with an equation that relates the voltage from the sensor to turbidity!

DIY Water Quality Meter Using a Turbidity Sensor Schematic Circuit Diagram 6

I conducted some preliminary tests recently with the aim of establishing communication between the DFR sensor module and my Arduino Uno. I successfully achieved this using the serial monitor. It’s important to note that when using the “DFR” sensor, in digital mode, we receive a signal output very close to the VCC level when the sensor is either not submerged or is in clear water (in analog mode, it’s slightly lower). Below is a straightforward Arduino code for a rapid test (connect the sensor module’s output to analog pin 1 and set its mode selector switch to the analog position).

void setup() {
  Serial.begin(9600);

}
void loop() {
  int sensorValue = analogRead(A1);
  float voltage = sensorValue * (5.0 / 1024.0);

  Serial.println ("Sensor Output (V):");
  Serial.println (voltage);
  Serial.println();
  delay(1000);
}

DIY Water Quality Meter Using a Turbidity Sensor Schematic Circuit Diagram 7

Later, I decided to go directly into the design of a luxurious Digital Turbidity Meter — more soon.

DIY Water Quality Meter Using a Turbidity Sensor Schematic Circuit Diagram 8

And Finally…

Keep note while coding for your microcontroller-based project that the equation included in the relationship graph is only applicable if the sensor gives out 4.2 V roughly at zero turbidity (clear water), and it’s only true within the range of 2.5 V to 4.2 V (3,000 to 0 turbidity)!

References (including but not limited to):

Tags

Related Articles

Leave a Reply

Your email address will not be published.

Back to top button
Close
Close