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Everything You Need to Know About Proximity Sensor Circuit

You use different types of sensors throughout your day, and you might not even know them! It is uncanny how these superb inventions of physics have made our lives so much easier. Since the advancement of technology, these sensors are undergoing incredible upgrades to provide you with more feasibility and edge. There is a large variety of sensors that are now a crucial component of huge consumer electronics.

Be it your AC, baking oven, street lights, or coolers, these sensors are everywhere, making your devices perform at their finest! Today, we cannot even imagine our lives without these sensors since they have been serving us efficiently due to their remarkable features.

We have picked the proximity sensor circuit to discuss in this post. You are going to have a look at these sensors from a different perspective which is going to be fun! So let’s hop onto it without any delay!

Systems of different Proximity Sensor Circuits

Before we jump onto the actual discussion, its time that we see what systems are appropriate for particular sensors to work:

  • PIR sensors (automatic door opening/closing system)
  • LDR sensors (automatic street lighting system)
  • Piezoelectric sensors (power generation system)
  • IR sensors (traffic signal system)
  • Ultrasonic sensors (obstacle detection system)

Proximity Sensor Circuit

proximity sensor circuit
proximity sensor circuit

A proximity sensor is a mechanism that is reliable for verifying the objects present near it that might touch it as well. Such a system works with electromagnetic radiation, and it can use electromagnetic fields in some cases. The electromagnetic field will change if the sensor detects any object lying around it. Now when we talk about proximity sensors, we will call this object the target of the sensor. There are different types of targets that you can place around a proximity sensor. These can be of plastic or metals. As per these targets, we get different types of proximity sensors which lead us to our next section!

We will go in-depth about these types of proximity sensors later in the next sections for you! 

Features of Simple Proximity Sensor Circuit

  • These are highly precise in the results.
  • This offer a short response time.
  • These have more longevity.
  • These work on non-contact detection phenomenon.

Principle of Proximity Sensor Circuit

  • As you know, the purpose of a proximity sensor is to detect the objects around it within the nominal range. The sensor will not detect non-metallic objects at all. 
  • There is a magnetic coil that generates the electromagnetic field for the sensor when the power supply energizes the coil.
  • After this, when an external disturbance influences this electromagnetic field, it will cause it to produce an eddy current that will cover the disturbance. The disturbance, in this case, is our target which will interfere with this electromagnetic field. It will also cause the load to reduce the intensity of the electromagnetic field. 
  • Now here is what happens: When you will bring the target closer to the sensor, it will boost the eddy current, which will cause the load to amplify the vibrations as well. It will reduce the strength of the electromagnetic field ultimately.
  • There is a trigger that will detect these vibrations based on the distance of the target and will turn the switch ON/OFF as per the condition.
  • The opposite will happen, and the vibrations will boost when you take the target away from the sensor.  

Major Types of Proximity Sensor Circuits


1. Inductive Proximity Sensor Circuit

These sensors do not need contact for their performance. 

  • Inductive proximity sensors use inductive law for object detection.
  • The distance of the metallic object determines the oscillations produced by the coil.
  • You can find this sensor in two variants in the market. One is the shielded version, and the other is the unshielded version. 

2. Unshielded Proximity Sensor Circuit

  • There is no disturbance in the electromagnetic field of the coil which means it will allow a higher range of detection. 
  • The oscillator, Schmitt trigger, coil, and output switch circuit make up an unshielded version of an inductive proximity sensor. 
  • When the coil gets energized due to current, it will produce an electromagnetic field. 
    When the sensor detects a metallic object, the eddy currents will cause changes in the inductance. 
    After this, the current will also change the final output on the whole. It happens with the sensor’s switch, which is responsible for monitoring. 
  • In the absence of a target, the sensor will keep vibrating, while in the presence of the target, it will cause the sensor’s switch to trigger. 
  • The use cases of this circuit are mostly in commercial areas where land mining and metal detection are important applications. 

3. Capacitive Proximity Sensor Circuit

  • These are also non-contact sensors and can detect metallic and non-metallic objects. It means these are multipurpose, unlike inductive proximity sensors.
  • When this sensor detects any peculiar shifts in the capacitance, it will notify or beep. 
  • It has the same components as the inductive proximity sensors.
  • However, there are two capacitor plates in this sensor, from which one is present inside the sensor, and the other is outside. 
  • You connect the internal plate with an oscillator, while the external plate will pair up with the detecting region of the sensor. 
  • An electrostatic field is important to make this system work. 
    When it comes closer to a target, the capacitance will increase, and it will also boost the oscillator’s gain. 
  • Applications like touch devices and moisture controllers often use capacitive proximity sensors. 
  • Ultrasonic Proximity Sensor Circuit
  • Such a sensor is useful for applications like automation and production.
    It will detect its target based on the nominal range or, in simple words, distance. 
    These sensors work on a frequency of 20 kilo-hertz, which is higher than the audible frequency range of humans.
  • It does its job by generating an ultrasonic signal and receiving them back.
    After this, it will determine the time disparity between the outgoing and incoming ultrasonic signals, which helps it to find out the distance of the target. 
    Just a transmitter and a receiver will make this circuit up. You can palace them together or separate them for individual units.

5. Optical Proximity Sensor Circuit

  • These are among the most affordable types of proximity sensors that you would ever know.
    You can trust them for automated applications, and they are easily adjustable within congested areas.
  • There is a light source for this sensor which will enable it to detect light. 
    Now there is also a light sensor which is basically a semiconductor that is reliable for producing light for once only. 
  • These sensors have important applications in copy machines, light fixtures, and alarm systems. 

6. Magnetic Proximity Sensor Circuit

  • It works by detecting the magnetic field around it, which means it can only detect the presence of a magnetic object.
  • When the object interacts with the sensor, it will trigger the sensor causing it to turn ON. 
    These are also non-contact sensors and work more efficiently than the other versions of proximity sensors. 
  • There are many principles of physics that a magnetic proximity sensor works on. These are reed switches, GMR inductive, and magnetoresistive. 
  • Major Applications of Proximity Sensor Circuit
  • We have grouped some of the fascinating applications of proximity sensors for you!
    Whenever you need to detect a metallic object, you can use a proximity sensor for this purpose.
    It not only detects the presence of an object, but it also determines the distance within the nominal range.
  • Smartphones also use proximity sensors.
  • Smart home appliances and home automation devices completely rely on proximity sensors.
  • Different industrial-grade tools and rolling mills also use proximity sensors.
  • The conveyor belts used in the factories and at the airports use such sensors to count all the items moving on them.
  • Tracking systems, distance measurement devices, electrical motors, and speed determination also work with proximity sensors.
  • You can use photoelectric proximity sensors for the purpose of detecting the presence of plastic objects.
  • Inductive proximity sensors are for detecting metallic objects, and the ultrasonic version will identify the target based on this distance. 
  • Some proximity sensors will detect both metallic and non-metallic objects.

Disadvantages of Proximity Sensor Circuit

Irrespective of the fact that proximity sensors have remarkable features and have significant applications in different domains. There are some considerable drawbacks of these sensors that you should know. There have been cases when complications occurred for the projects since the users were unaware of these drawbacks of proximity sensors. So make sure you are choosing the right variant of a proximity sensor for yourself!

  • Temperature and humidity can influence the performance of proximity sensors.
  • Their designs are complex, and there is no margin of negligence when it comes to their construction.
    The range through which they can detect the objects is variable as per the sensor’s type
    Some types are expensive to produce as well.
  • The inductive sensors are less accurate than other types of the proximity sensors.
  • Technical glitches in the proximity sensors can ruin the entire device.




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