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Smart Cities PRO Sensor Probes

Group of sensors designed for Smart Cities applications

The main applications for Libelium Waspmote Smart Plug & Sense! Cities PRO model are noise maps (monitor in real time the acoustic levels in the streets of a city), air quality, waste management, structural health, smart lighting, etc.

Libelium provides many different sensor probes depending on what is going to be measured. For Smart Cities model following sensor probes can be used.

Temperature sensor probe

Sensor specifications (MCP9700A)
  • Measurement range: [-40ºC , +125ºC]
  • Output voltage (0ºC): 500mV
  • Sensitivity: 10mV/ºC
  • Accuracy: ±2ºC (range 0ºC ~ +70ºC), ±4ºC (range -40 ~ +125ºC)
  • Supply voltage: 2.3 ~ 5.5V
  • Response time: 1.65 seconds (63% response from +30 to +125°C).
  • Typical consumption: 6µA
  • Maximum consumption: 12µA

The MCP9700A is an analog sensor which converts a temperature value into a proportional analog voltage. The range of output voltages is between 100mV (-40°) and 1.75V (125°C), resulting in a variation of 10mV/°C, with 500mV of output for 0°C.

Soil Temperature sensor (DS18B20) probe

Sensor specifications (DS18B20)
  • Measurement range: [-55ºC ,+125ºC]
  • Output voltage (0ºC): 500mV
  • Resolution: 12bits (0.0625ºC)
  • Accuracy: ±0.5ºC (range -10ºC ~ +85ºC)
  • Supply voltage: 3.0 ~ 5.5V
  • Response time: 1.65 seconds (63% response from +30 to +125°C)
  • Typical consumption: 1mA
  • Conversion time: 750ms

The DS18B20 is a temperature digital sensor which provides an accurate measurement and a high resolution (of up to 0.065ºC) which communicates with the Waspmote’s microcontroller through the 1-Wire bus. It has been encapsulated in a plastic seal that isolates it from humidity, thus allowing to use it in wet environments as long as for temperature measurement in soil or liquids.

Ultrasound sensor probe

Sensor specifications (XL-MaxSonar®-WRA1™)
  • Operation frequency: 42kHz
  • Maximum detection distance: 765cm
  • Maximum detection distance (analog output): 600cm (powered at 3.3V) - 700cm (powered at 5V)
  • Sensitivity (analog output): 3.2mV/cm (powered at 3.3V) – 4.9mV/cm (powered at 5V)
  • Power supply: 3.3 ~ 5V
  • Consumption (average): 2.1mA (powered at 3.3V) – 3.2mA (powered at 5V)
  • Consumption (peak): 50mA (powered at 3.3V) – 100mA (powered at 5V)
  • Usage: Indoors and outdoors (IP-67)

The MaxSonar® sensors from MaxBotix output an analog voltage proportional to the distance to the object detected. This sensor can be powered at both 3.3V or 5V, although the detection range will be wider for the last one. The XL-MaxSonar®-WRA1™ sensor is endowed with an IP-67 casing, so it can be used in outdoors applications, such as liquid level monitoring in storage tanks.

Humidity Sensor Probe

Sensor specifications (808H5V5)
  • Measurement range: 0 ~ 100%RH
  • Output signal: 0.8 ~ 3.9V (25ºC)
  • Accuracy: <±4%RH (at 25ºC, range 30 ~ 80%), <±6%RH (range 0 ~ 100)
  • Supply voltage: 5VDC ±5%
  • Operating temperature: -40 ~ +85ºC
  • Response time: <15 seconds
  • Typical consumption: 0.38mA
  • Maximum consumption: 0.5mA

This is an analog sensor which provides a voltage output proportional to the relative humidity in the atmosphere. As the sensor’s signal range is outside of that permitted to the Waspmote’s input, a voltage divider has been installed which converts the output voltage to values between 0.48 ~ 2.34V.

Luminosity sensor probe

Sensor specifications (LDR)
  • Resistance in darkness: 20MO
  • Resistance in light (10lux): 5 ~ 20kO
  • Spectral range: 400 ~ 700nm
  • Operating temperature: -30ºC ~ +75ºC

This is a resistive sensor whose conductivity varies depending on the intensity of light received on its photosensitive part. The measurable spectral range (400nm – 700nm) coincides with the human visible spectrum so it can be used to detect light/ darkness in the same way that a human eye would detect it.

Noise sensor probe

Sensor specifications (POM-2735P-R)
  • Sensitivity: -35±4dB
  • Impedance: <2.2kO
  • Directivity: Omnidirectional
  • Frequency: 20Hz~20kHz
  • Supply voltage: +3V (Standard), +10V (Maximum)
  • Maximum current consumption: 0.5mA
  • Sensitivity reduction: -3dB a 1.5V
  • Maximum sound pressure level: 114.5±10dBSPL approximately
  • S/N ratio: 60dB
  • Noise Level: 26 +/-1 dBA
  • Stage Measurement range: 50dBA~100dbA

The POM-2735P-R, introduced in the Smart Cities board to monitor the environmental noise, is an omnidirectional microphone with an almost flat response in the whole frequency range of human hearing, between 20Hz and 20kHz. A circuit to filter the signal to adapt it to the A decibel scale and output a continuous voltage readable from the mote’s processor has been introduced. When sold along with a microphone, the Smart Cities board is supplied calibrated by Libelium to return an output in the range between 50dBA and 100dBA with an accuracy of ±2.5dBA. The calibration data associated to the microphone reading is stored in the microcontroller’s EEPROM, between addresses 164 and 185.

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