Acquire information – The different sensors – mymaxicours, the different types of sensors | Superprof

How to automate a toll barrier

A logical electrical signal is an electrical signal that can only take two values. These two values ​​are named high state And low state.

Acquire information – the various sensors

Know and differentiate the different types of sensors.

  • There are three families of sensors: Tor (all-orrian) sensors, analog sensors and digital sensors.
  • The product signal is different depending on the type of sensor used: analog signal, logical signal or coded logic signal.
  • The sensor can be active or passive, depending on whether or not it needs to be integrated into a circuit to operate.
  • The sensor can be proprioceptive or exteroceptive, depending on whether it achieves measures locally or in a global manner.

1. The nature of the sensor output signals

A sensor is a component of information withdrawal which develops, from a physical quantity, another physical quantity of a different nature (generally electric).

The sensors can be characterized according to the nature of the output signal.

has. Tor sensors (all-orrian)

A Tor sensor (outer-rien) is a sensor that transforms a physical phenomenon into a logical electrical signal.

A logical electrical signal is an electrical signal that can only take two values. These two values ​​are named high state And low state.

The high condition often corresponds to the highest voltage that the signal can take, commonly 3.3 V or 5 V, and the low state corresponds to the lowest voltage, commonly 0 V.

  • Logical signals are also named binary signals.
  • TOR sensors are also called detectors, binary sensors or logical sensors.

Principle
A threshold value is defined. When the input quantity is below the threshold, the sensor output is 0, when the input size is greater than the threshold, the sensor output is 1.

In practice, the Tor sensor has two separate thresholds to prevent the exit from becoming unstable when the input is very close to the threshold.

  • So that the sensor exit passes to the upper state, the input size must pass over the high threshold.
  • For the sensor outlet to go to the low state, the input size must pass below the low threshold.

The gap between the high threshold and the low threshold is called hysteresis.

Example
An infrared motion detector may detect the presence or lack of movement in a room.

Microcontrollers and microprocessors are able to directly use the signals provided by Tor sensors, as they are binary signals.

B. Analog sensors

A analog sensor provides an analog electrical signal which is proportional to the measured physical magnitude.

An analog electrical signal is an electrical signal which can take all possible values ​​between a minimum value and a maximum value.

The transformation operation is called the transduction. The signal tension will be directly linked to the value of the captured physical phenomenon.

Example
An analog temperature sensor may provide a voltage proportional to the temperature it measures. For each increase of 1 ° C from 0 ° C, the tension will increase by 0.1 V.

Noticed
It is rare that the tension is simply proportional to the value of the phenomenon, but in general the formula of passage from one to the other is given in the technical sheet of the sensor.

An analog sensor provides an analog tension which will not be directly usable by a digital brain, such as a microcontroller or one microprocessor.

Noticed
Arduino, microphone cards: bit and those based on ESP8266 have a microcontroller; Raspberry Pi cards, computers and smartphones have microprocessors.

For a microcontroller or a microprocessor to be able to use the information of an analog sensor, the signal will be beforehand to be digitized by a component called a Can.

Noticed
Most cards with a microcontroller have an integrated CAN. This is generally not the case with products with a microprocessor.

vs. Digital sensors
A digital sensor provides a digital signal proportional to the size to be measured.

A digital sensor is a sensor that makes successively:

  • the transduction of a physical phenomenon into analog electrical signal;
  • The digitization of the analog signal in logical signal.

The product logical signal is not a simple binary signal like that produced by the Tor sensors: it is a Coded logic signal. This means that he uses language, called standard or communication protocol, To transmit complex information in binary form as a number, a letter, a word, a full text, etc.

Noticed
Digital sensors are also named coders.

Example
A digital temperature sensor will measure and then transmit the value of 16.9 ° C to a microcontroller, using the UART protocol. Here is what the coded logical signal looks like that allows this value to be transmitted.

Noticed
Here are some common communication standards or protocols used by coders: UART, I2C, SPI, Onewire.

Each data that the digital sensor transmits is therefore a logical signal made up of several binary values ​​(in the high state or the low state): these binary values ​​are called bits. All the bits that make it possible to transmit a data is called a frame.

Example
The frame that the digital temperature sensor transmits to microcontroller by UART has 11 bits.

  • Bit 1 is a start bit, which indicates that the frame begins.
  • Bits 10 and 11 are stop bits that indicate that the frame ends.
  • Bits 2 to 9 are data bits which allow the data to be transmitted. Here, the binary value is worth ( 1 0 1 0 1 0 0 01 ))2, which corresponds to decimal to (169)10 which is the value that the sensor transmits for 16.9 ° C.
    Noticed : 1 × 2 0 + 0 × 2 1 + 0 × 2 2 + 1 × 2 3 + 0 × 2 4 + 1 × 2 5 + 0 × 2 6 + 1 × 2 7 = 169

Whenever the digital sensor wants to transmit a value to the microcontroller or a microprocessor, it must send it a full frame.

Example
The following signal shows how the temperature transmission takes place by the digital sensor for approximately 14 s, in the event that it transmits a new temperature value every 4 s.

Microcontrollers and microprocessors are able to directly use the signals provided by digital sensors because they are binary signals.

Noticed
It is nevertheless necessary to specify the communication protocol used and indicate how to read it in the microcontroller or microprocessor. This will be done using software libraries.

2. Active sensors and passive sensors
has. Passive sensors

THE passive sensors need to be integrated into a circuit with a diet.

Here are some examples of passive sensors.

The internal resistance of a resistive sensor varies with physical size.

  • Temperature measurement by resistance to platinum wire or thermistor.
  • Stress measurement by stress gauge.
  • Light intensity measurement by photoresistance.

Inductance is the ability of an electronic dipole to store magnetic energy when it is crossed by a current.

The value of the inductance L an inductive sensor varies with physical size. An inductive sensor only detects metal objects.

The inductive sensor emits a magnetic field. Metal objects disrupt this magnetic field. It is this disturbance which is detected by the sensor.

  • Metal object detection.
  • Displacement measure by variable inductance.
  • Effort by magnettoelastic sensor.

The capacity corresponds to the ability of an electronic dipole to store energy when it is crossed by a tension.

Capacity value VS a capacitive sensor varies with physical size.

  • Detection of the presence of an object whatever its nature.
  • Detection of the level of a liquid in a tank.
  • Moving and position measurement (one of the capacitor’s reinforcements is on the object whose displacement we want to measure).

B. Active sensors

In the case of active sensors, The input quantity, or its variations, directly generates an energy (voltage, current, electrical load).

This energy is generally low, these sensors therefore require the use of amplifiers. Here are some examples of passive sensors.

Photoelectric or photovoltaic sensor

Photoelectric (or photovoltaic) sensors are based on the release of electrical loads in the material under the influence of light radiation or, more generally, an electromagnetic wave.

Piezoelectric sensor

The application of a mechanical constraint to certain so -called piezoelectric materials (quartz for example) leads to the appearance of a tension between their opposite faces.

Hall effect sensor

A magnetic field B and an electric current I create in a semiconductor material a voltage proportional to B And I .

Example
Current measurement with an amplemmetrical pliers.
3. Proprioceptive and exteroceptive sensors

In mobile robotics, it is important to distinguish between proprioceptive sensors and exteroceptive sensors.

has. Proprioceptive sensors

Sensors proprioceptive perform their measurements in relation to what they perceive locally from the moving of the robot.

Example
We can measure the angular movements of the wheels of a robot, which allows to reconstruct its trajectory provided that the wheels do not slip (slippage, skating). It is a proprioceptive sensor.

B. Exteroceptive sensors

Sensors exteroceptive based on measures taken from the global environment (absolute benchmark).

Example
The location by a laser turret of optical tags fixed in the robot movement environment allows an absolute measurement. It is an exteroceptive sensor.

How to automate a toll barrier ?

As part of VSEs, the student has personal work to do who puts him in a situation of responsibility. This activity is a training in Scientific procedure and/or technological approach. VSEs must call on the intelligence of concrete situations because the reality of the engineer’s profession is not essentially to solve problems but to identify and pose them clearly.

The objective of VSEs is to allow the student to develop in particular the following qualities and capacities:

  • Open -mindedness,
  • Personal initiative,
  • Faculty of bringing several logics closer, in particular by decompartmentalization of disciplines,
  • Critical spirit, capacity for requirement, deepening and rigor,
  • Ability to the experimental imagination,
  • Ability to collect information, analyze it, communicate it.

This activity aims to enhance intellectual curiosity and in -depth work rather than speed,
also evaluated within the framework of the control of the acquisition of disciplinary knowledge.

The object of very small businesses is therefore not the acquisition of additional disciplinary knowledge which is also carried out within the framework of the teaching program.

Thanks to the implementation of a new working method and a diversification of study subjects, very small businesses help to enhance various scientific profiles.

In order to achieve these objectives and prepare for the competition tests, students, supervised
By teachers, will develop various activities and approaches, for example:

  • Highlighting and formulating a problem,
  • Observation and analysis of a phenomenon or industrial system,
  • Research and exploitation of documentation,
  • The preparation and production of files and presentations,
  • The development of arguments during a scientific interview,
  • The examination and discussion of the solutions and justifications of the choices made.

Initiation to the student’s scientific approach

During VSEs, the student has personal work to do who puts him in a situation of responsibility. This activity is
in particular an initiation, training in the scientific research process, leaving him to ask questions before trying to answer them. Indeed the questioning prior to the development or research of solutions is a common attitude that scientists and engineers practice. Scientific research leads to The development of real objects and real objects which participate in the process of building the
science at work and bear the name of scientific and technological discoveries and innovations.

By registering resolutely in the perspective recalled above, necessarily interdisciplinary perspective, the student’s work will highlight the construction of one of the objects of thought or real mentioned above adhering to the imposed theme and will appropriate a significant part of the research process
scientist involved: problematic, modeling, scientific criticism, realization. Through some of these aspects, the student will make his personal contribution, which will take the form best suited to the subject treated: experience, representation, explanation, conceptualization, manufacture, scientific dialogue.

TPE contents

The work provided will therefore include a Student’s personal production (observation and description of natural or artificial objects, collection, sorting and processing of data, highlighting of phenomena, experimentation, exploitation of the computer tool, modeling, investigation of new fields of application. ) carried out as part of the subject chosen adhering to the theme. This production can in no case be limited to a simple synthesis of information collected, but must include a “Added value” brought by the student.

Students carry out this work individually or in a small group (maximum five students per group). Each student must engage personally on all of the work presented.

Advice for the realization of his TPE

The choice of subject

How to use your passions to succeed professionally?

For a choice of intelligent subject, it is advisable to get closer to his passions And hobbies And to talk about it actively with your teachers to bind them with the theme of the year. Do not hesitate to be original in your choice !

Validate your choice

Once you have chosen your subject, you must set up a problematic which will serve as a spine for your project. Indeed, you must be certain of the scientific level of your project so that it is at least equal to that of the preparatory classes. It is here that your teachers will support you since they know the program of the year and will thus be able to guide you on the choice of tools and knowledge to be provided and use. So you will know if your idea is feasible so as not to waste too much time.

The subject being defined, the problem posed, you have to get to work as quickly as possible, by surfing the enthusiasm of the subject’s promises. What to start to succeed in TPE ? Here are some tracks.

Start the project

The first experience

To make a good choice of first manipulation, do not hesitate to Call on your physical teacher or preparers who can advise you fairly complete protocols. You can also get closer to the internet.

Do you serve old contests

They will allow you to give birth to ideas and reflections in your minds since they correspond to the level that will be expected from you at the end of the year when you have to present your project. You can then use the laws, but also the demonstrations or even Scientific names having worked on a theme similar to yours.

Use the books !

How to create a bibliography?

Of course, it is advisable to use scientific journals or even theses or doctorate in order to expand your bibliographic references. Then think of archive links or at Download PDF Documents that will be useful to you.

Know whether to continue or change the subject

After the All Saints holidays, you will have to take stock of your work and make a choice:

  • If you like your subject and you start to have results which can lead to complete developments so confirm your choice of subject and deepen your problem while taking note and synthesizing the results already obtained.
  • If you like your subject but when you short of your experiences you have discovered a more interesting track So keep this subject, but change the problem to make it more relevant. Know in any case that the work started is not lost because it allowed you to know more about the subject.
  • If you don’t like the subject or it seems too difficult to achieve So it’s still time for you to change the subject. Before deciding, do not hesitate to ask your teachers for advice.

Theory and experiences

Above all, you should not neglect the theoretical part of your TPE Because it must be perfectly mastered. This is why it can sometimes be relevant to revise its scientific ambition downwards. Indeed, you are not asked to restore the entire thesis but to understand the heart of your subject and to know how to restart all of this.

Do not have experiences to say that you have experiences since an experience must be used for your project and confirm your hypothesis or raise a question. Think of uncertainties and note the different handling hazards, Do not hide them but exploit them : you are not robots, you have the right to make mistakes and you must recognize them.

When you need equipment for your manipulations, do it properly and in writing to facilitate the work of laboratory. And even if your experience does not happen as planned and gives you a completely different result from what you expected, take note in a corner in order to use it may later.

Tips for the handling and practical part of TPE

The development of a manipulation protocol

It is important to quickly Start thinking about the path of your manipulation. Indeed, you must know where you want to go and what you have to demonstrate to start considering the means to use. This is called the writing of your experimental protocol.

It’s your work plan. At draft, Note your ideas. Take them one by one and think about how you plan to implement and carry out the experience.

  • Does this experience answer the question asked in the problematic ? ;
  • Am I able to perform this experience ? ;
  • Do I have the knowledge necessary to interpret the results of my experience ?

Once this checklist has been validated, you can write your experimental protocol on your own.

For that, write out And legibly Using short sentences and clear words. No need to drown in too advanced explanations. You must use action verbs that only reflect the acts that you will perform during your experience.

At the end of writing the experimental protocol, remember to mention the security measures to be taken for the realization of your experience. Mention the necessary safety equipment: glasses, gloves, blouse, suction hood, etc.

You can also enhance the protocol of an experience scheme by precisely detailing the material used and treating your drawing.

Put your hypotheses

Write them down hypotheses that you wish demonstrate after your experience. Indicate in which cases they are validated and in which cases they are refuted.

Carry out the requested experience

Now that the protocol and the hypotheses have been installed and established, you can put yourself in practical. Use the protective equipment that is useful for carrying out the experience. Proceed with calm and rigor. Follow the steps of the experimental protocol step by step. Do not hesitate to take notes during the experience, you will be able to account for it. Subscribe your problems encountered or possibly the changes you had to make to the protocol to make the experience feasible.

Write the report

In your report, you must report the result of your experience while validation or in refuting Your assumption (s). Note the course of your experience and the conclusions you have drawn from it. You can add comments on the realization of the experience.

We can also add documents such as photographs experience or even sketch and graphics.

Conclude manipulation

Finally, you must write a conclusion. In the latter, take the statement and provide an answer, using your experience to justify it. Take care of this part, it is she who results in your handling and your note depends a lot.

Another advice: graphics

Do not forget to indicate the title, THE quantities corresponding to the abscissa And the ordinate with their unit And the scale used.

The “points” will be preferentially “straight” crosses: horizontal line + clearly visible vertical line!

If the curve is supposed to be a right, check the alignment of the points (and specify it in the report) and trace an “average” line. Calculate his coefficient (his slope), almost always used to conclude and above all, Represent the uncertainties !

How to make a beautiful graphic?

Subject example: the different types of TPE 2010 sensors: how to automate a toll barrier ?

Different types of sensors

The world around us is made up of countless sensors. They can take very varied forms and be designed for very diverse uses. It was therefore necessary to provide our model with several sensors

Small introduction to sensors (families, specificities etc.))

This information is the fruit of research that has covered the first four weeks of our TPE.

A sensor is a device Who transforms the state of a physical quantity observed in usable size. In other words, the sensors take information on the behavior of the operative part and transform it into a Useable information by the command part (therefore in an electrical form). The goal is to develop the system to the characteristics of the external environment.

In sequential automated systems, the control part deals with logical or digital variables. The information delivered by a sensor may be logic (2 states), digital (discreet value) or analog.

We can characterize the sensor according to two criteria:

  • depends on measured ; We are talking about positions, temperature, speed, strength, pressure, etc.
  • according to the character of the information delivered ; We then speak of logical sensors also called all or nothing sensors (tor), analog or digital sensors.

We can then classify the sensors by two categories, sensors at contact which require direct contact with the object to be detected and the sensors of proximity. Each category can be subdivided into three categories of sensors: mechanical, electric, pneumatic sensors. To choose a specific sensor, you must therefore try to delimit the main characteristics that we want to attach it. Overall, here are the characteristics that we have sought to delimit:

  • L’extent of the measurement : It is more or less the difference between the smallest signal detected and the largest noticeable.
  • There sensitivity : It is the smallest variation in physical quantity that a sensor can detect.
  • There speed : this is the reaction time of a sensor between the variation in the physical quantity that it measures and the moment when the information is taken into account by the command part.

All sensors have two distinct parts. A first part of the role of detecting or measuring an event and a second part whose role is to translate an event into a signal understandable by a PC control system. To properly choose a sensor, it is therefore important to define (3rd math course):

  • The type of event to detect
  • The nature of the event.
  • The greatness of the event.

Depending on these parameters, one or more choices can be made for a type of detection. Other elements can make it possible to target the sensor to use precisely.

  • Its performance.
  • Its congestion.
  • Its reliability.
  • The nature of the signal issued by the sensor (electric, pneumatic etc. ))
  • His price.

The analysis of these criteria was expensive in time but the choice of the sensor seemed crucial to us.

We have also documented on the nature of the different types of sensors that existed. We prefer to present them to you in a table according to their specificities so as to differentiate them well.

How to ask for the online math help ?

The most common types of sensors

Sensor type Description, use, operation and example
Inductive Produce in the sensor axis a magnetic field oscillating. This field is generated by system made up of a self and a capacity mounted in parallel. When a metal object enters this field, there is a disturbance of this field, attenuation of the oscillating field.
Capacitive Local sensors that make it possible to detect metal or insulating objects. When an object falls into the sensitive electrodes detection field, the frequency of oscillations is modified at the same time as the capacity capacity of the capacitor of the capacitor.
Photoelectric or optical sensor It consists of a light transmitter associated with a receiver. The detection of an object is done by cutting the light beam
Position sensor These are contact sensors. They can be equipped with a roller, a flexible stem, a ball. The information given by this type of sensor is of all or nothing and can be electric or pneumatic.
They (flexible blade switch) A sensor They is a local sensor consisting of a flexible blade sensitive to the presence of a mobile magnetic field. When the field is under the blade, it closes the contact of the circuit causing the switching of the sensor. This sensor goes directly to a cylinder and makes it possible to detect positions other than extreme positions. To use this type of sensor, it is necessary to use a cylinder with a magnet on the piston.
Sensors at flight Long -on sensors are contact sensors. Contact with the object to be detected can be done either by a flexible rod, or by a ball. To be able to function properly, these sensors must be coupled with a relay for sensor at leak. The sensor is powered by the relay. The air can then escape from this sensor by an orifice provided for this purpose. When the ball or the flexible blade is moved to its accommodation, it obtains the air drain orifice and the leakage sensor is triggered and emits a signal to the pressure to the pressure.
Temperature sensor Pyrometer, thermometer, PT100 probe, thermocouple, thermistor.
Pressure sensor Bourdon tube, aneroid capsule, piezo-electric, vibrant rope, barometer, hypsometer.
Light sensor Photodiode or phototransistor, photographic sensor, photo cell.
Flow sensor Turbine flow meter, oval wheels, orifice plate, pitot tube, vortex effect flow meter, flow meter, electromagnetic, venturi flow meter, ultrasonic flow meter, ion flow meter, mass flowmeter.
Current sensor Hall Effect Current Sensor, Shunt.
Sound sensor Microphone, hydrophone.

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