Basic Electronics Used in Environmental Monitoring

The research of many scientists aims to ensure that our planet is maintained to benefit future generations, monitoring and measuring the environment over long time periods with costly equipment. However, the creation of cheaper and accessible devices would mean that “Citizen Scientists” could monitor the environment. This comes with several challenges, such as lack of power, extreme environmental conditions, and poor communications channels.

Why Should We Care?

Earth (Pale Blue Dot) as seen from Voyager 1 in 1990. Image: NASA

Figure 1: Earth (Pale Blue Dot) as seen from Voyager 1 in 1990. Image: NASA.

We only have one home planet with no backup. Therefore, we must look after it, making information about the quality of our air, water, and soil, vital. Monitoring our environment has many advantages, such as:

  • Food Supply: Allowing fully educated decisions on crop rotations to make sure that everyone has food
  • Human Health: There is a direct link between human health and our environment. Environmental factors (e.g. mold proliferation) can be a leading culprit in the causation of illness.
  • Economic: Worldwide, massive insurance claims will be made as homes and properties are flooded due to sea levels rising.

Sensor Selection Considerations

PT3001 Optical Sensor from Texas Instruments. Image: TI.

Figure 2: PT3001 Optical Sensor from Texas Instruments. Image: TI.

One of the most vital aspects of measuring our environments is the sensor. These components convey physical characteristics into electricity, allowing quantification. Ensuring the correct sensor is chosen for the correct application is vital and therefore, many parameters need to be evaluated:

  • Absolute versus Relative: Absolute sensors produce an output which is autonomous from the operating environments. Contrariwise, a Relative sensor's output necessitates the output to be compared a known quantity (e.g., fixed voltage)
  • Passive versus Active: Active sensors need a power supply, while passive sensors directly alter the physical stimulus to form an electrical signal
  • Sensitivity: Ratio of the output signal against a known physical stimulus
  • Response Time: Speed at which the output signal changes relative to alterations in the physical stimulus
  • Range: Minimal and maximal physical stimulus which can be detected. For example, the OPT3001 sensor from Texas Instruments can monitor ambient lights at a range of 0.01 lux to 83 k lux
  • Linearity: A perfect sensor has a 1:1 relationship between the stimulus change and the output signal range. However, many sensors require correction for the characteristic non-linear relation of stimulus to output.
  • Resolution: The stimulus smallest change which can be detected
  • Digital or Analog Output: The differences between the capabilities in terms of conversion between digital and analog output
  • Accuracy: Sensirion provides very proficient temperature and humidity sensors under their SHT3X product line. Whereas the SHT31 have a precision of 2%, the SHT30 sensors have a +/- 3% precision
  • Drift: The degradation of the sensor activity which is monitored as a modification in the unit of measure per unit of time
  • Operating Life: Each type of sensor has a different life expectancy

Sensirion SHT3X Temperature/Humidity Sensor Development Board. Image: Sensirion.

Figure 3: Sensirion SHT3X Temperature/Humidity Sensor Development Board. Image: Sensirion.

Therefore, many different factors should be considered when selecting a sensor for environmental monitoring. Further questions may be; how often will it need to be maintained, how often is data output required or will it need to be time stamped?

Additional Design Considerations

However, the performance of the sensor is not the only factor which must be considered when creating an environmental monitoring solution. A high-performing sensor is not useful if it is constantly running out of power. Therefore, energy harvesting technologies in association with low-power sensors could allow for continuous and reliable monitoring of the environment.

Bluetooth® Low Energy allows environmental sensors to efficiently communicate to a smartphone. Shown: The Nordic Semiconductor nRF51822 Bluetooth Smart Beacon Kit. Image: Nordic Semiconductor.

Figure 4: Bluetooth® Low Energy allows environmental sensors to efficiently communicate to a smartphone. Shown: The Nordic Semiconductor nRF51822 Bluetooth Smart Beacon Kit. Image: Nordic Semiconductor.

Another issue is communication: how will you receive the data from the sensor? Two options are available: through long distance machine-to-machine (M2M) interactions, such as the Long Range Wide Area Networks (also known as LoRaWAN™), or through the user's smartphone or tablet, such as the Broadcom WICED™ Sense Kit. This option can result in less laboratory time and more testing time in the real world.

Enabling Citizen Science through DIY Electronics

STEAM (science, technology, engineering, art, and mathematics) topics have been attracting lots of discussion in the past 10 years. There has been an increase in Citizen Science, endeavoring to enhance scientific research by guaranteeing that everyone can investigate their local environments.

A popular device for Citizen Science is Arduino 101 microcontroller board. This device is an updated version of the Arduino Uno, with enhanced computing power. Utilizing its strong Intel® Curie™ System-on-a-Chip (SoC) construction, this board comprises a powerful 32-bit Quark™ SE microcontroller, Bluetooth Low Energy communications, an onboard Real Time Clock (RTC), a 6-axis accelerometer/gyroscope, and battery charging circuitry.

Arduino 101 enables Makers to join with Citizen Science to the monitor local environment.

Figure 5: Arduino 101 enables Makers to join with Citizen Science to the monitor local environment.

If an off-the-shelf tool is not available, the integral functionality allows a cheap instrument to analyze specific environmental conditions. The functionality of the RTC is especially important for research to allow for date/time stamping, vital for analyzing correlations and data relationships. As the affordability and accessibility of these devices improve, so will the ability to identify and hopefully prevent environmental changes.

A Better Tomorrow, By Design

For the foreseeable future, humans will continue to live on Earth. This, therefore, requires environmental care to ensure that future populations have the resources required to survive. This care requires monitoring, to be able to assess our contributions and keep improving our sustainability.

Therefore, the creation of low-cost environmental analysis technologies aids our understanding without straining the organizations that are devoted to caring for the environment.

This information has been sourced, reviewed and adapted from materials provided by Mouser Electronics.

For more information on this source, please visit Mouser Electronics.

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