Wireless Sensor Network Design for
Intelligent Occupancy-Based Lighting
Control
1.0 Assignment Header and Context
The following report details the selection and technical specifications of sensors intended for
a Wireless Sensor Network (WSN) project focusing on intelligent energy management within
built environments.
Detail
Specification
Reg. No.:
BL.EN.U4CSE22015
Institution:
Amrita Vishwa Vidyapeetham
Campus:
School of Computing, Bengaluru Campus
Examination:
B. Tech. Degree Examination – Oct 2025
Branch
Computer Science and Engineering,
Seventh Semester
Course Code:
19CSE339 – Wireless Sensor Networks
1.1 Specialization Area
The project specializes in Sustainable Smart Building Automation and Energy
Management.
This area integrates WSN technology to control critical building systems, primarily lighting
and potentially Heating, Ventilation, and Air Conditioning (HVAC), based on real-time
environmental and occupancy data.1 The goal is to maximize energy efficiency and improve
occupant comfort, aligning the system design with modern Industrial IoT (IIoT) frameworks. 3
2.0 Sensor Details (For each sensor)
The proposed WSN architecture utilizes three primary sensors: a Passive Infrared (PIR)
motion detector for occupancy sensing, a Light Dependent Resistor (LDR) for ambient light
detection, and a DHT22 sensor to measure temperature and humidity for environmental
integration.
2.1 Sensor 1: PIR Motion Sensor (HC-SR501)
Field
Detail
Sensor Name
HC-SR501 PIR Motion Sensor
Cost
Specifications
₹ 400 – ₹ 600 (Highly cost-effective,
approximately $5-7 USD equivalent) 4
Operating Voltage: 4.5V – 20V DC. Power
Consumption: 65mA max. TTL Output: 3.3V
(High) / 0V (Low). Sensing Range:
Adjustable, 3 meters to 7 meters (up to
detection cone). Delay Time: Adjustable,
0.3 seconds to 5 minutes.5
Applications
Core technology for Occupancy Detection,
Home and Building Automation, Security
Systems, and indispensable for EnergySaving Initiatives through automated
lighting and environmental control.8
Calibration & Accuracy Details
Calibration: Self-calibration required
upon initial power-up, typically lasting 60
seconds.6 The system must remain passive
during this warm-up period to avoid false
triggers. Adjustments: Sensitivity
(detection range) and delay time (output
duration) are set using two onboard
potentiometers.6 Accuracy: Provides a
digital, binary output (motion detected/not
detected).
Lifetime
Designed for robust, long-lasting
performance. The typical operational
lifespan is several years under stable
indoor environmental conditions.8
Remarks
The adjustable delay time is a critical
feature, allowing engineers to fine-tune
the system to prevent lights from switching
off prematurely ("flickering") when
movement is intermittent. It is highly
compatible with microcontrollers.6
Available At
Buy HC SR501 PIR Motion Sensor Circuit
Module In India | Robu
2.2 Sensor 2: Light Dependent Resistor (LDR, 7mm Photoresistor)
Field
Detail
Sensor Name
Light Dependent Resistor (LDR, 7mm
Photoresistor)
Cost
Extremely low, typically ₹ 50 – ₹ 100 for
the raw component or module. (One of the
most budget-friendly sensor options).11
Specifications
Sensor Type: Cadmium Sulfide (CdS)
Photoresistor. Max Operating Voltage: Up
to 150V DC. Max Power Consumption:
100mW. Dark Resistance: M$\Omega$.
Light Resistance: k$\Omega$. Response
Time: Fast, 20ms (Rise) and 30ms (Fall).11
Applications
Ambient light measurement, Automatic
Street Light Control, Dusk/Dawn sensing,
and core function for Daylight Harvesting
in smart lighting systems.13
Calibration & Accuracy Details
Calibration Method: No physical
calibration is performed. Accuracy is
defined by setting a static software
threshold value based on analog-to-digital
converter (ADC) readings, which correlates
to the desired switching point.14
Limitation: The LDR is non-linear and is
not suitable for precise lux
measurement.11
Lifetime
High durability, often several years when
operated within specified voltage and
temperature parameters indoors.
Sensitivity can be affected over time by
dust accumulation.11
Remarks
Simple and reliable component for binary
light detection (Light/Dark). The sensor’s
performance is susceptible to variations in
ambient temperature and humidity,
requiring careful physical placement away
from thermal sources.11
Available At
Buy 5800B Light Dependent Resistor LDR
White Color Online | Robu.in
2.3 Sensor 3: Temperature and Humidity Sensor (DHT22 / AM2302)
Field
Detail
Sensor Name
DHT22 (AM2302) Digital Temperature and
Humidity Sensor
Cost
Moderately low cost, typically ₹ 450 – ₹
700 (US$ 4-10). It offers better precision
than the cheaper DHT11.15
Specifications
Operating Voltage: 3.3V to 6V DC.
Temperature Range: to . Humidity Range:
0% to 100% RH. Current Use: 2.5mA max
during conversion. Sampling Rate: Low,
maximum of 0.5 Hz (one reading every two
seconds).17
Applications
Environmental monitoring, data logging,
crucial integration for maintaining optimal
comfort levels, and supporting holistic
energy management through linked HVAC
control.1
Calibration & Accuracy Details
Accuracy: Temperature: ; Humidity: .
Calibration: Factory calibrated with digital
output.15 Stability: Exhibits long-term
stability drift of per year.16
Lifetime
Limited operational lifetime, typically 1–2
years under continuous, high-duty-cycle
operation. This is primarily due to the
humidity sensing element’s chemical
degradation.16
Remarks
Provides high precision measurements
relative to its cost, making it ideal for
environmental conditioning feedback. The
slow, 2-second sampling interval is a
critical constraint for fast real-time control
algorithms.17
Available At
Buy DHT22 Digital Temperature and
Humidity Sensor Module In India
3.0 Conclusion and Project Rationale
The intelligent lighting system utilizes the HC-SR501 PIR Motion Sensor, the 7mm
Photoresistor (LDR), and the DHT22 Temperature and Humidity Sensor. This sensor suite
forms a foundational WSN node aimed at robust and cost-effective smart energy
management.
Summary of Sensors Selected for Project
These sensors were strategically chosen to offer a balanced approach to the project
requirements, maximizing functional coverage while minimizing deployment cost. The PIR
sensor provides reliable input on human presence, essential for activation.8 The LDR governs
the conditionality of activation, preventing unnecessary light use during high ambient daylight
levels.13 The inclusion of the DHT22 elevates the system's capabilities, transforming it from a
mere lighting control unit into a node capable of gathering environmental data necessary for
integrated HVAC control and overall comfort optimization.1
The selection criteria prioritized low cost and high compatibility with standard embedded
platforms (like Arduino or ESP microcontrollers), ensuring rapid prototyping and deployment
feasibility.1 The operational lifespan of the PIR and LDR sensors is adequate for typical project
duration, providing a stable monitoring environment. Although the DHT22 has a known limited
lifespan (1–2 years), its superior precision over alternatives justifies its use in environmental
monitoring, necessitating appropriate long-term maintenance strategies to manage its drift.16
Collectively, these sensors enable the efficient automation of lighting and HVAC systems,
delivering significant reductions in energy wastage and operational costs crucial for modern
sustainable buildings.
Works cited
1. Commercial Smart Building IoT Lighting Controls | Lutron, accessed on October
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7, 2025, https://commercial.lutron.com/us/en/commercial-solutions/smartbuildings
Smart Industrial Lighting Solutions - Open Lighting Product Directory (OLPD),
accessed on October 7, 2025, https://www.shine.lighting/products/smartindustrial-lighting/
HC-SR501 PIR Motion Sensor – Lonely Binary, accessed on October 7, 2025,
https://lonelybinary.com/products/hc-sr501
HC-SR501 PIR Motion Sensor - Canada Robotix, accessed on October 7, 2025,
https://www.canadarobotix.com/products/2327
HC-SR501 Passive Infrared (PIR) Motion Sensor - Handson Technology, accessed
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http://www.handsontec.com/dataspecs/SR501%20Motion%20Sensor.pdf
HC-SR501 PIR Motion Sensor - oemsecrets.com, accessed on October 7, 2025,
https://www.oemsecrets.com/articles/hc-sr501-pir-motion-sensor
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https://ezmation.com/sensors/63-hc-sr501-pir-motion-sensor.html
How to Use HC-SR501 PIR motion sensor: Pinouts, Specs, and Examples | Cirkit
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https://docs.cirkitdesigner.com/component/8ac6bdb1-4a5f-4113-bc41ba56280614f8/hc-sr501-pir-motion-sensor
HC-SR501 PIR Motion Sensor Arduino Tutorial (3 Examples) - Makerguides.com,
accessed on October 7, 2025, https://www.makerguides.com/hc-sr501-arduinotutorial/
10. LDR 7mm Light Sensor Module for Smart Automation & Security, accessed on
October 7, 2025, https://bigyanproject.com/en/ldr/ldr-sensor-7mm
11. 12MM PHOTOSENSITIVE LDR SENSOR - iFuture Technology, accessed on
October 7, 2025, https://ifuturetech.org/product/12mm-photosensitive-ldrsensor/
12. Ambient Light Sensors: Types, Applications and Selection Tips - DigiKey
TechForum, accessed on October 7, 2025, https://forum.digikey.com/t/ambientlight-sensors-types-applications-and-selection-tips/44800
13. Arduino Light Sensor: Learn to Setup a Photoresistor (LDR) - YouTube, accessed
on October 7, 2025, https://www.youtube.com/watch?v=XtldqC3dzXU
14. Temprature and Humidity Sensor-DHT22 Online @ Best Price - Matha Electronics,
accessed on October 7, 2025,
https://www.mathaelectronics.com/product/dht22-sensor/
15. Compare DHT22, DHT11 and Sensirion SHT71 - KandRSmith.org, accessed on
October 7, 2025,
https://www.kandrsmith.org/RJS/Misc/Hygrometers/calib_dht22_dht11_sht71.htm
l
16. DHT22 temperature-humidity sensor + extras : ID 385 - Adafruit, accessed on
October 7, 2025, https://www.adafruit.com/product/385