Types of sensors for target detection and tracking

The ultimate goal when a robot is built is to be optimized and to be compliant with all specifications. To meet the requirements sometimes you can spend many hours just to sort and identify the sensors that would be the best for an application like detecting and tracking an object. In this article, we explore all sensor types that can be used for target detection and tracking as well as features and the types of applications where they can be used.

Selecting the right sensor is not a strict process. This is about eliminating all the wrong choices based on a series of question aiming to eliminate first the technology that underlying the sensor and then the product that it doesn’t fit to the robot requirements.

When we use the word target, we refer in the same time at a small ball, at an object like a chair, or even at a human that stay in front of the robot.

To select the best sensor from a variety of products and manufacturers is a hard work especially when you’re a beginner and try to build a simple robot. In few words the sensor has to be selected in concordance with your targets size, shape and range. All of these three features have to be on the same line with the specification of the robot. But even so, it is hard to define the best sensor since the performance and precision of this depend on many factors.

Principle of an active sonar (photo source wikipedia.org)

Principle of an active sonar (photo source wikipedia.org)

A sensor is a sophisticated device that measures a physical quantity like speed or pressure and converts it into a signal that can be measured electrically. Sensors are based on several working principals and types of measurements. In our case almost all types of sensors emit signals and measure the reflection to make measurements.

There are many sensors that can be used for a simple application like line following (IR LED and a Photodiode, LED and LDR, etc.), but this is a simple case when a simple sensor can be selected. A complicated case is when you have to track an object and the budget is limited to purchase a mini computer like Raspberry Pi. In this case it can be used an ultrasonic sensor to scan from side to side till the sensor detect a drop in distance (at this stage it detects the edge of the object and from now on the sensor see only the background). The scanning process continues back to the point where the object is with left and right scanning.
This is one of the cases when expensive products can be replaced with cheap sensors.

In the following, you can explore the features of sensors that can be used for detecting and tracking a target.

Criteria to choose the right sensor

With so many models available on the market from various vendors would be very useful to know from where you can start. A good starting point is to know certain features, and some of them are given below:

  • Type of Sensor – the presence of an object can be detected with proximity sensors, and there are several kinds of sensor technologies including here ultrasonic sensors, capacitive, photoelectric, inductive, or magnetic. Tracking objects can works using proximity sensors (ex. : ultrasonic sensors), or for advanced applications generally it is used image sensors (ex.: webcams) and vision software like OpenCV;
  • Accuracy – the accuracy is very important in detecting and tracking objects, and it is useful to choose sensors with accuracy values between desired measurement margins;
  • Resolution – a high resolution can detect smallest changes in the position of the target;
  • Range – involves choosing the sensors based on measurement limits and compared with the desired detection range of the robot;
  • Control Interface – to interface the sensor you have to know the types of the sensors. A wide range of sensors are 3-wire DC types, but there are many more types including 2-wire DC or 2-wire AC/DC;
  • Environmental Condition – any sensor has its operational limits usually these are the temperature and humidity;
  • Calibration – calibrating the sensors is an essential step in to ensure efficiency and more accurate measurement;
  • Cost – depending on the budget allocated to a project, you can select the sensor or the sensors that can be used to build the robot;

Sensor classification based on property

  • Proximity sensors – several sensor technologies are used to build proximity sensors: ultrasonic sensors, capacitive, photoelectric, inductive, or magnetic;
  • Motion detectors – these sensors are based on infrared light, ultrasound, or microwave/radar technology;
  • Image sensors – these are digital cameras, camera modules and other imaging devices based on CCD or CMOS technology;

Starting from the above information and combining with the below features for each type of sensor separately, you are now able to find the appropriate sensor and start building any robotic application.

Each sensor type has its characteristics that make from this little device better for a certain task or replaceable from other tasks. For example, an ultrasonic sensor works fine for solid objects and becomes lazy for soft or fuzzy objects. Also, some sensors are unable to make the difference between a static object and a human. All of these characteristics have to be clear before to choose the right sensor/sensors for your robot.

Light sensor

A light sensor can be included in the proximity sensor category, and it is a simple sensor that changes the voltage of Photoresistor or Photovoltaic cells in concordance with the amount of light detected. A light sensor is used in very popular applications for autonomous robots that track a line-marked path.

Color sensor

Different colors are reflected with different intensity, for example the orange color reflects red light in an amount greater than the green color, and this is the color sensor. This simple sensor is in the same range with light sensor, but with a few extra features that can be useful for applications where the robot has to detect the presence of an object with a certain color, or to detect the types of objects or the surfaces.

Touch sensor

The touch sensor can be included in the proximity sensors category and are designed to sense objects at a small distance with or without direct contact. This sensor is designed to detect the changes in the capacitance between the on-board electrodes and the object making contact.

Ultrasonic sensor

These sensors are designed to generate high frequency sound waves and receive the echo reflected by the target. These sensors are used in a wide range of applications and are very useful when it is not important the detection of colors, surface texture, or transparency.

Advantages of Ultrasonic sensors

  • the output value is linear with the distance between the sensor and the target;
  • sensor response is not dependent on the colors, transparency of objects, optical reflection properties, or by the surface texture of the object;
  • these sensors are designed for contact-free detection;
  • sensors with digital (ON/OFF) outputs have excellent repeat sensing accuracy;
  • accurate detection even of small objects;
  • ultrasonic sensors can work in critical conditions such as dirt and dust;
  • they are available in cuboid or cylinder forms, which is better for a freedom design;

Disadvantages of Ultrasonic sensors

  • ultrasonic sensors must view a high density surface for good results. A soft surface like foam and cloth has low density and absorb the sound waves emitted by the sensor;
  • could have false responds for some loud noises such as air hoses;
  • the ultrasonic sensors have a response time with a fraction less than other types of sensors;
  • an ultrasonic sensor has a minimum sensing distance, which should be taken into consideration when you choose the sensor;
  • some changes in the environment can affect the response of the sensor (temperature, humidity, pressure, etc.);

Infrared sensor

An infrared sensor measure the IR light that is transmitted in the environment to find objects by an IR LED. This type of sensor is very popular in navigation for object avoidance, distance measured or line following applications. This sensor is very sensitive to IR lights and sunlight, and this is the main reason that an IR sensor is used with great precision in spaces with low light.

Advantages of Ultrasonic sensors

  • infrared sensors can detect infrared light over a large area;
  • they can operate in real-time;
  • the IR sensor uses non-visible light for detection;
  • they are cheap sensors;

Disadvantages of Ultrasonic sensors

  • this sensor is very sensitive to IR lights and sunlight;
  • it has a weakness to darker colors such as black;

Sonar sensor

The sonar sensor can be used primarily in navigation for object detection, even for small objects, and generally are used in projects with a big budget because this type of sensor is very expensive. This sensor has high performances on the ground and in water where it can be used for submersed robotics projects.

Laser sensor

A laser light is very useful for tracking and detection a target located at a long distance. The distance between sensor and target is measured by calculating the speed of light and the time since light is emitted and until it is returned to the receiver.
A laser sensor is very precise in measurement and in the same time is very expensive.

Image sensor

Most popular combination for detection and tracking an object or detecting a human face is a webcam and the OpenCV vision software. This combination may be the best in detection and tracking applications, but it is necessary to have advanced programming skills and a mini computer like a Raspberry Pi.
Using an image sensor can be built a wide range of applications, and some of these are listed below:

  • face detection and tracking;
  • tracking and detecting objects in colors;
  • detect specific shapes in images;
  • detect corners of triangles from an image;
  • detect the position of an object on 2D surfaces;
  • it can acquires and prioritizes targets;

Sensors: Different Types of Sensors, engineersgarage.com;
Component measuring touch, electronics.stackexchange.com;

68 comments » Write a comment

  1. I am involved in robotic design for non-civilian purposes.

    My first endeavour, several years ago, was to develop an ‘Operating System’ for a friend’s fighting wheeled vehicle. There were some rules including overall weight.

    As a result of our ultimate success, there were rule changes. Apparently using a bottled gas source to actually burn the other vehicle, a metal clad device, was never considered.

    My OS also had ‘radiation’ detection: ultrasonic, infra-red and radio. Since our vehicle used very non-standard frequencies we were able to to ‘blind’ our opponents by simply swamping the frequencies they employed with different devices. No 40 kiloHertz ultrasound for us, we were way off that frequency. Likewise with the laser optical system, we used the speed radar trap band. With radio, none of the industrial, scientific and medical (ISM) radio bands for us, again, off frequency makes a big difference. It is simple to even blind Furtaba spread spectrum systems.

    The ‘flipping’ robots abilities are easily reduced by using hinged stainless rods that simple prevent a flipper from getting to close.

    This interest in fighting vehicles has now translated into a different field and a very profitable one, too.

    Thinking outside the box is key.

    • Hi,
      You seem like you know what your doing, so can you help me. I’m trying to make a kid an infrared Universal Studios Interactive Wand gift out of a Lego Mindstorm (so it can be easily fixed.) Any idea how to get the sensor to track the reflected light to activate a command when it is drawn in a certain shape?

  2. Hi,
    I’m looking for sensors that detect whether or not they are on the same linear plane as one another. For instance if two sensors where on a level surface and a third was on a board 2″ higher than the others. I want to be alerted of the difference, and the sensor creating the irregularity. Do these types of sensors exist? and where would i be able to find them?

    • Hi Ben,
      I happen to be looking for exactly the same sensor that you mentioned. Any luck finding them? Would really appreciate it if you can help me provided you found a solution.



    • Hi Ben, if you still looking for a solution, you could use laser so when it hits the object you could trigger it. Hope it helps.

      Best of luck


  3. Hi, can you suggest me, if exists, a sensor or set of sensors, to real-time scan 3D real space in a range of 2..10 mt? I’ d like to detect small object incoming from any 3D direction. Better if no motors are required (sensors should be motionless).
    Thank you.

  4. hi, i need to create wristbands that can sense each other. so I need to create a circuit with sensors and led’s. so that when the wristbands touch or are in extremely close proximity to each other the led’s on each wristband light up. can anyone tell me how to do this?

  5. thanks for these information. may you give some idea that how can ardino uno and ultrasonic sensors both use in smat street lighting system?

    • why do u wanna use ultrasonic for smart street lighting systems? they just need on timer or off timer in general cases or u use photodetector in conjuction with a relay. ultrasonic sensors can only be needed if you want power savings to a great level where lights glow when it detects a person or a car and close when it dissappears but that needs frequent uses of relay switching which will cost more for hardware and maintenance. Variable brightness can be good option in conjunction with ultrasonic sensors but again it needs relays and logic.

  6. Hi. we are working on a project that collects floating garbage in the sea. What sensor would i use to detect the floating object and directs the bin motor to go near the garbage? thanks.

  7. Can ultrasonic sensor use to detect any person within 30 km range?
    If yes,then,how? I want to make a project to detect anybody through this sensor.Kindly help.

  8. Hello .. I am doing a project to place a seismic sensor in the ground and to detect human , automobile presence based on the frequency … is it possible ? does anyone have experience regarding this?

  9. what type of sensor should we use if we want to search one item from 100 similar items kept in-front of us. Example i have 100 bags containing items of 100 different customers. When customer arrives to collect his bag then his bag should raise beep sound etc, this will save time when compared with manual effort to find his bag.

  10. Hi Calin Dragos-Georges
    Great article.
    If i want to distinguish between a dense/hard surface and a soft surface (e.g. human nails versus skin) which sensor can i use


  11. Hi all,
    This is a quite short, descriptive and useful article. I’m new to sensors and I’m working on automation in waste segregation. I’d like to know if these sensors can detect the percent or amount of the target present. Can these be integrated to a PLC ?

  12. I want to develop a device that detects the ambulance coming that way and gives a kind of warning so that the traffic can be cleared before the ambulance reaches that spot.this would prevent the ambulance from getting stuck in the traffic for hours.are there sensors to detect the path the ambulance is travelling through .can this be displayed on some screen like thing?

    • for that, there should be a gps device to be installed in the ambulance. so that you can connect microcontrollers and you can get notified

  13. hey, i am intrested to build a robot goal keeper which can track the ball and block them. can any one suggest me the materials and type of sensors that i have to use?

  14. Hi all,
    i am searching for a sensor which can detect the minimum distance of 4mm, the distance distance 4mm is between robot and work piece. At the same time the sensor should detect the ground surface of 400*300mm. its urgent can any one help me
    Thank you in Advance


  15. Hello everyone,
    Iam searching for a sensor, that should detect whether doorlocked are not and when it detects that door has locked, it should send a signal to my computer,Can anyone suggest me which type of sensor should i use?

  16. Hello Everyone,

    I am looking for a sensor which can detect space between two objects. For example, there are two chairs and there is some space between them. Sensor should detect that space and calculate if that space is enough to place another in their. It need to be long range and use outdoor.

  17. hii guys,

    I am really unable to find the right sensor for my project. Can you people suggest me which one will be the good choice.

    Aim of the project is to pick the white color object from open environment (basically in 3D environment) where a plenty of objects will be available and also object will be movable with wind speed. Object Maximum distance is from 0.2 to 2 Meters.

    My sensor has to work in open Environment and it has to identify white color object where a plenty of objects will be available in the environment. First preference is To pick up the near by object and goes on upto last object available in the environment.

  18. Hi I want to detect another object front of my sensor and also identify its location, direction with respect to my position.

  19. I’m interested in a sensor, probably ultra sensor to detect objects and automobiles etc approaching too close. Also are these sensors protective from giving off radiation?

  20. I am looking for a sensor that could identify a target on a person in group of people.
    Also wondering what could a target be that would identify the person.
    Sorry I am new to thus.

  21. hi , i m working on smart car parking system . i m looking forward to use RFID tags and video surveillance . will this be a good option . what else technology can i use??

  22. Hey I want to know if there’s any sensor that could detect the locations and deliver a message related to that through headphones?

  23. Hello everyone,
    Could you please make some suggestions on what type of sensor I could use if I want to detect very small objects (up to 3mm in size or smaller)? Additional factors which could affect the visibility of the object are grass, animal’s hair… Are there any which you would recommend and are they going to be accurate enough considering these obstructions in the environment?

    Thank you very much

  24. Hi. I’m in need of a sensor that can detect and reject defective parts on a production line… Any suggestion? Would be grateful.


  25. HI ,

    I am looking for a sensor(non vision related) which can be attached to a small objects to be tracked later wherever there are on the floor. Since the cost is a barrier, can you suggest a sensor which can help me in this?

  26. Hi this Linda I’m looking of a sensor that can be used on two object each object will have it own sensor when this two object has interacted to each other they must sense one another and keep the information of the sensor that it interacted with the sensor should be have the unique serial number or name to recognise each other please advise me with any similar sensor that can delive the same solution thanks

  27. Hi. I have a question. What sensor do you think would be the best fit to detect an object that has placed in a lets say a box? and why would that be the best fit?

    Thank in advance,

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