sensors

Sensors

Basic Electronics

Analog Sensors

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Digital Sensors

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As many of you know, sensors act as the perceptive organs of our electronic devices, enabling them to interact with the physical world.

In the simplest terms, a sensor is a device that detects and responds to input from the physical environment. This input could be light, heat, motion, pressure, or any number of environmental phenomena.

The sensor then outputs a signal, typically an electrical one, that we can read or further process.

temperature sensor with arduino

A sensor is a device that detects and responds to some type of input from the physical environment.

The specific input could be light, heat, motion, moisture, pressure, or any one of a great number of other environmental phenomena.

The output is generally a signal that is converted to a human-readable display at the sensor location or transmitted electronically over a network for reading or further processing.

Types of sensor

Sensors can be broadly classified into two categories based on the type of output signal they produce: analog and digital sensors.

Analog Sensors

Analog sensors produce a continuous output signal or data.

The output signal is a direct representation of the measured property.

This output signal could theoretically take on any value within a certain range, which means it can provide more precise measurements compared to digital sensors.

Examples of analog sensors -

  • Thermocouples

    These are temperature sensors that produce a small voltage proportional to the temperature difference between two different types of metal.

  • Photodiodes

    These are light sensors that produce current proportional to the amount of light striking the diode.

  • Piezoelectric sensors

    These sensors generate an electrical charge in response to mechanical stress and are often used for measuring pressure, acceleration, or force.

One of the challenges with analog sensors is that the signal they produce can be susceptible to noise, which can lead to inaccurate readings.

tools_flat_head In addition, to use the data from an analog sensor in a digital system (like most modern computers and microcontrollers), the analog signal must be converted to a digital signal using an Analog-to-Digital Converter (ADC).

Digital Sensors

Digital sensors, on the other hand, produce a digital output. This means the signal is non-continuous and takes on discrete values.

The output from a digital sensor can often be more stable and accurate than an analog sensor, and it is ready to be used by digital systems without needing to be converted.

Examples of digital sensors -

  • Digital Temperature Sensors

    These sensors produce a binary output representing the temperature. One common example is the DS18B20 digital thermometer, which provides 9-bit to 12-bit Celsius temperature measurements.

  • Infrared Proximity Sensors

    These sensors can output a simple binary (on/off) signal to indicate whether an object is within a certain range.

  • Digital Light Sensors

    These sensors, like the TSL2561, provide a digital output that corresponds to the amount of light they detect.

In some cases, a sensor might have an analog front end (for the actual sensing part), but then include an ADC to provide a digital output.

straightenThis can give you the best of both worlds: high-precision measurements, and easy integration with digital systems.

The choice between analog and digital sensors depends largely on the specifics of the application, including the precision required, the environment in which the sensor will be used, and the nature of the system that will be processing the sensor's data.

Embedded Systems and Sensors

Embedded systems and sensors are closely intertwined. In the broadest sense, an embedded system is a computer system that has a dedicated function within a larger system.

It's called "embedded" because it's often part of a complete device that includes hardware and other mechanical parts.

Sensors play a crucial role in many embedded systems. They act as the interfaces between the physical world and the computing system, enabling an embedded system to interact and react to its environment.

Data Acquisition
The sensor detects changes in its physical environment — these could be temperature, pressure, light, motion, or any other environmental parameters. The sensor converts these physical parameters into an electrical signal.
Signal Processing
The signal from the sensor is often weak and may contain noise. Before the data can be used, it must be amplified, filtered, and otherwise processed to make it useful. This is often done by analog circuits or by an Analog-to-Digital Converter (ADC) if the sensor is analog.
Data Analysis
Once the signal is processed, it's sent to the microprocessor or microcontroller within the embedded system. This is the "brain" of the system, which takes the data from the sensor and performs calculations or makes decisions based on the input.
Action
Based on the processed data and the embedded system's programming, the system might take some action. For instance, if the embedded system is a thermostat and it receives data indicating that the room temperature is too low, it might send a signal to turn on the heat.
Feedback
In many cases, the action that the embedded system takes will affect the environment in some way, which will then be detected by the sensor, creating a feedback loop. This allows the system to continuously monitor and adjust to its environment.

Sensors provide embedded systems with the information they need about their environment to perform their functions effectively.

Without sensors, many embedded systems would not be able to interact meaningfully with their environment.

From smartphones to industrial controllers, from home appliances to advanced medical devices, embedded systems with sensors are vital to our modern way of life.

Analog Sensors

These sensors produce a continuous output signal or voltage which is generally proportional to the quantity being measured. For example, a temperature sensor in your room might measure temperatures from 0 degrees Celsius to 50 degrees Celsius, and produces a voltage output that is directly proportional (e.g., 0 Volts = 0°C, and 5 Volts = 50°C). Examples include thermocouples, strain gauges, and photocells.

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Digital Sensors

These sensors produce a binary output signal or a discrete output. This means that these sensors only provide high or low signals. For example, a button sensor will only indicate whether it is pressed or not (0 Volts = not pressed, 5 Volts = pressed). Examples include encoders, digital pressure sensors, and touch sensors.

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