Proximity Switches: Everything you Need to Know

Have you ever wondered how automatic doors work? Or how alarms trigger when someone gets too close to them. The proximity switches are what make the magic happen.

However, it’s possible to mistake a proximity switch for a proximity sensor. But in truth, both devices are pretty different.

This article will teach you everything about the proximity switch and what makes it different from a proximity sensor.

Are you ready? Let’s begin!  

What is a Proximity Switch?

As the name implies, proximity switches can detect objects when they come close. Proximity switches can also determine an object’s distance.

Interestingly, these switches can measure proximity through various means, including electric, magnetic, or optical means.

More importantly, the proximity switch’s ability to detect the presence of objects makes it an essential piece in a wide range of security applications.

Proximity switches can also use an electromagnetic or magnetic field to detect the presence of metal objects. Some proximity switches can even work like metal detectors.

Additionally, proximity switches are non-contact switches. Hence, most people prefer them over direct-contact switches. Proximity switches are also immune to wear and tear because they don’t need repeated physical contact.  

Proximity Switch Working Principle

The proximity switch requires two circuits: a driver and a sensor circuit. The sensor circuit is what detects an object and sends an electrical signal to the driver circuit.

The driver circuit is transistor-based. Also, it can use a PNP or NPN transistor, but it depends on the application.

When the driver circuit receives the signal, it activates the transistor and output. The sensor also sends another signal to deactivate the transistor if the object goes beyond the detection range.  

Types of Proximity Switches

Different proximity switches can detect various objects in different ways. These types of proximity switches include:

• Optical proximity switches
• Inductive proximity switches
• Capacitive proximity switches
• Ultrasonic proximity switches

Let’s take a closer look at what these switches can do.  

Optical (Photoelectric) Proximity Switches

Optical Proximity Switch

 

This proximity switch equips a light source and a photocell like other optical sensors. Also, the optical switch can detect objects when there’s a change to the switch's amount of light.

Usually, this happens when an object interrupts or reflects the light beam coming from the emitter diode.

In addition, the optical proximity switch is pretty flexible and can work for various safety applications.  

Inductive Proximity Switches

These proximity switches can detect nearby metallic targets without requiring physical contact. Inductive proximity switches also boost high switching speeds, making them popular for automation applications.

The inductive proximity switch uses an oscillator-driven coil. The oscillator also creates electromagnetic fields that travel to the switch’s active section.

Whenever a metallic object or an object with metal targets comes close to the switch, it reduces the electromagnetic field and activates or deactivates the switch.

Interestingly, inductive proximity switches can determine metallic objects' position and check if a device has a metallic rotational part.

No doubt, the inductive proximity switch is the go-to for metal objects.  

Capacitive Proximity Switches

A capacitive proximity switch can measure non-metallic objects, including conductive and non-conductive objects. Plus, it uses capacitance change to determine the proximity of an object.

With a capacitive proximity switch, you can detect solid, liquid, or powdery objects. Plus, the switch equips itself with two electrodes with varying coupling capacitance.

Also, the switch’s coupling capacitance will only change if the object enters the electrical field of the electrodes.  

Ultrasonic Proximity Switches

Ultrasonic proximity switches are popular in the automation field for accurate distance measurement. It can also detect objects but are more efficient at measuring object distance.

These proximity switches are reliable and can measure distances even in the air. How does it work? The switch can generate and send ultrasonic pulses up to 10 meters.

When an object reflects these pulses, the switch will detect the echoes and calculate the distance.  

Proximity Switch Symbol

The proximity switch symbol diagram is similar to a mechanical limit switch. However, one thing that differentiates both symbols is the diamond shape enclosing the switch.

The diamond shape signifies the device is active, and the proximity switch is always active.

Additionally, many proximity switches don’t generate outputs that require physical contact. Instead, they use transistors to configure their output elements. Hence, they can source or sink current.  

Proximity Switch Symbols

 

Applications

The proximity switch can work for various industrial, security, and automation applications. For instance, many industrial processes require monitoring physical quantities. Hence, to reduce the stress of using human eyes.

These switches can activate alarms when the quantity is not enough or stop the process when it’s enough. They can also deactivate machines when in critical or dangerous conditions.

Let’s take a closer look at the applications of each type of proximity switch.  

Optical Proximity Switch Applications

Here are the things you can do with an optical proximity switch:

• This proximity switch is helpful in mechanical engineering.
• You can find optical proximity switch in printing machines.
• It also works for access control applications.
• They’re an essential part of conveyors and packing machines.
• Lastly, these proximity sensors offer excellent textile, plastic, and paper processing performance.

 

Inductive Proximity Switch Applications

The applications of an inductive proximity switch include:

• These switches can serve as metal detectors
• Inductive switches can also locate metallic parts in any machine or device.

Capacitive Proximity Switch Applications

Here’s what you can do with this sensor:

• You can use this switch for level indication.
• The switch is also great for object counting.
• With this switch, you can control levels in containers (glass or plastic).
• It also works for automation control.

 

Ultrasonic Proximity Sensor Applications

You can use this switch for the following range of applications:

• You can measure the height of any stack.
• You can also measure levels and detect different object positions.
• It also works for measuring thickness and detecting limits.

 

What is the Difference Between a Proximity Sensor and the Proximity Switch?

Proximity Sensor vs. Proximity Switch

 

As we mentioned earlier, it’s easy to confuse a proximity switch and a proximity sensor. But it’s pretty easy to differentiate the two apart.

The proximity sensor is a detector that detects objects within its detection range.

In contrast, the proximity switch is a controller that activates or deactivates a circuit when the sensor sends its signals. The signals can signify the presence or absence of an object.  

Wrapping Up

The proximity switch is not only crucial for object detection but also for contactless control applications. Also, it’s worth mentioning that a proximity switch will always be in idle condition until an object enters its detection range.

Additionally, each type of proximity switch offers a unique way of detecting and measuring proximity. However, they all have one thing in common: the need for an electric circuit to help detect objects.

What’s your opinion on the proximity switch? Feel free to let us know and contact us if you have any questions.