This document discusses various sensors that can be used in IoT applications, including light sensors, temperature sensors, moisture sensors, rain sensors, gas sensors, barometric pressure sensors, and radiation sensors. It provides brief descriptions of common sensors for each category, such as LDR light sensors, DHT11 and LM35 temperature sensors, soil moisture sensors, rain drop sensors, MQ gas sensors, BMP180 barometric pressure sensors, and GUVA-S12SD UV radiation sensors. Application examples and specifications are given for each sensor type.

1. Electronics
Sensors in IoT Applications
Leopoldo Armesto
Senior Lecturer
Universitat Politècnica de València
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2. Outline
Light sensor
Temperature sensors
Moist sensor
Rain sensor
Gas sensors
Barometric pressure sensor
Radiation sensor
And more…
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3. Light SensorLight Dependent Resistor (LDR): Its resistance varies depending on the amount of visible light received.
Typical circuit application:
LDR Calibration: The curve voltage-luminance is nonlinear.
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KY-018

4. Digital Temperature Sensor
DHT11 provides:
Relative humidity provided in %.
Temperature provided in Celsius with degree precision.
Uses one digital signal for transmitting and receiving data.
4 KY-015
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5. Analog Temperature Sensor
Analog temperature sensor LM35.
Linear response. Resolution: 10mV/C
Precision: 0.5C at 25C temperature.
Range: −55°C to 150°C
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KY-070

6. Digital Temperature Sensor
Digital temperature sensor 18B20 uses 1-wire interface and allows to connect multiple sensors just
using one digital pin.
Temperature in Celsius and Kelvin.
Temperature alarm handler
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KY-001

7. Moist Sensor
Soil/moist sensor FC-28 with two electrodes.
Analog output is proportional to resistance changes of soil moist.
Digital output activated when the signal is higher than a threshold value adjustable with a potentiometer.
Voltage decreases with moist. Typical values around 2.5V slightly moist soil and 4~5V for dried soils.
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8. Rain Sensor
Detects rain drops by measuring the resistance of the circuit board. The more water the lower the resistance.
Analog output is proportional to the amount of rain drops.
Digital output activated when the signal is higher than a threshold value adjustable with a potentiometer.
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Rain sensor
Signal amplifier

9. Gas Sensors
Gas sensors can detect among many type of gases: LPG, butane, propane, methane ,alcohol, Hydrogen, smoke, etc…
The working principle is based micro aluminum oxide ceramic tube a tin dioxide sensitive layer, measuring
electrode and heater.
Requires calibration of ‘clean air’ resistance to provide measurements in ppm.
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MQ gas sensors

10. Barometric Pressure Sensor
Barometric pressure sensor. It measures the absolute pressure of air.
Range from 300 to 1100hPa with accuracy 0.02 hPa.
It can also measure altitude and temperature.
Requires altitude at sea-level (depends on your location)
I2C interface.
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BMP180

11. Radiation Sensor
Analog UV light sensor GUVA-S12SD.
Light range 240-370nm.
Analog output (0~1200mV).
UV-index
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UV-index 0 1 2 3 4 5
Vout (mV) <50 227 318 408 503 606
UV-index 6 7 8 9 10 11
Vout (mV) 696 795 881 976 1079 1170
GUVA-S12SD

12. and more…
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RFID Card reader Camera Barrier sensorLimit contacts

13. Electronics
Sensors in IoT Applications
Leopoldo Armesto
Senior Lecturer
Universitat Politècnica de València
13