Our Project Journey

TU (Hmawbi)

Electrical Power Engineering

Project Showcasing

Ultrasonic Sensor

In this Smart Greenhouse project, HC-SR04 ultrasonic sensor module is used as a water level sensor. The HC-SR04 Ultrasonic Sensor is a distance measuring sensor that uses sound waves (ultrasonic waves) to detect how far an object is. It works on the same principle as how bats detect objects in the dark—by sending sound waves and measuring the echo time. In a greenhouse project, it can be used to measure water levels, detect object distance, or even monitor plant growth height.

A common four-pin ultrasonic sensor module, often used for distance measurement in robotics and other electronics projects. The sensor features four main connections: VCC (Voltage Common Collector, the power supply pin), Trig (Trigger, the pin used to initiate the ultrasonic burst), Echo (the pin that provides a pulse whose width is proportional to the distance measured), and GDN (Ground, the common reference point for the circuit). These four pins are essential for connecting the module to a microcontroller, which manages the timing of the trigger pulse and interprets the resulting echo pulse to calculate the distance to an object.

Components of the HC-SR04 Ultrasonic Sensor The HC-SR04 module mainly consists of four main components :

            
1. Transmitter (Trig Pin)
2. Receiver (Echo Pin) 
3. Control Circuit 
4. Microcontroller Interface Pins

Working Principle :

      
1. The microcontroller (like Arduino) sends 
   a 10 µs pulse to the Trig pin. 
2. The sensor emits 8 ultrasonic bursts at
   40 kHz. 
3. These waves hit an object and bounce back 
   to the receiver. 
4. The sensor measures the time taken for 
   the echo to return. 
5. Distance is calculated using the formula 
   as shown in picture.

Advantages :

1. Can measure distances precisely (usually within ±3 mm).
2. Works without touching the object (safe for plants or water).
3. Affordable and simple to connect with Arduino or 
   similar controllers.
4. Measures from 2 cm to about 400 cm (4 meters).
5. Works both day and night, unlike optical sensors.

Its Disadvantages :

1. The speed of sound changes slightly with air temperature 
   and moisture, which may affect accuracy.
2. Soft materials absorb sound waves; angled surfaces reflect
   them away.
3. Not suitable for very large areas.
4. Obstacles between the sensor and object can cause false 
   readings.

Fig : Circuit Diagram of Smart Water Level System

Power Supply

1. The main 5V Supply connects to the Arduino Uno R3 
   Development Board through the USB Port with a blue wire.
2. The Arduino provides power to the Breadboard, connecting 
   its 5V pin to the red positive rail and the GDN pin to the 
   black negative rail.
3. The Ultrasonic Sensor's VCC and GDN pins are powered directly 
   from the Breadboard's positive and negative rails.
4. Similarly, the Display Module's VCC and GDN pins also connect
   to the Breadboard power rails for their operation.
5. A separate 5V Battery powers the high-current components, 
   connecting its positive terminal to the positive input of 
   the Mini DC-DC Converter.
6. The Battery's negative terminal connects to the negative input 
   of the Mini DC-DC Converter.

Sensor and Display Connections

1. The Ultrasonic Sensor's Trig (trigger) pin connects 
   to the Arduino's Digital Pin 6 (yellow wire) to start 
   a distance measurement.
2. The Sensor's Echo (receive) pin connects to the Arduino's 
   Digital Pin 5 (blue wire) to read the measured distance time.
3. The Display Module's SCL and SDA pins connect to the 
   Arduino's A5 and A4 analog pins, respectively, 
   for I2C communication.

Pump Control Connections

1. The 1 Channel Relay's VCC and GDN pins connect to the 
   Arduino's 5V and GDN pins for its own power.
2. The Relay's IN (input) pin is connected to the Arduino's 
   Digital Pin 7 (green wire) to turn the relay on or off.
3. The output of the Mini DC-DC Converter's positive terminal 
   connects to the positive terminal of the 5V Water Pump.
4. The Converter's negative terminal connects to the COM (common) 
   terminal of the 1 Channel Relay.
5. The negative terminal of the 5V Water Pump connects 
   to the NO (normally open) terminal of the 1 Channel Relay 
   with a red wire.

Circuit Diagram of Smart Water Level System

1. The system uses an Ultrasonic Sensor to measure 
   distance or perhaps the water level in a tank.
2. The main controller is an Arduino Uno R3 Development 
   Board which manages all the inputs and outputs.
3. A Display Module is included to show information such as 
   distance readings or the system's status.
4. The high-current 5V Water Pump is powered by a separate 
   5V Battery not the Arduino's power supply.
5. A 1 Channel Relay acts as an electrically controlled switch
   to turn the Water Pump on and off.
6. The Mini DC-DC Converter is likely used to provide a regulated 
   and clean power source for the Water Pump.
7. The Water Pump is wired to the Normally Open (NO) terminal of 
   the relay meaning it's off by default.
8. The Display Module uses the I2C communication protocol 
   requiring only two data wires SCL and SDA.