Proximity Sensors

Welcome, guys, in this lecture. And now we will be talking about proximity sensors or in more depth, we will be talking about capacitive and inductive sensors. Now, as the name states, proximity sensors will be activated when an object comes close to the sensor, unlike the limit switches, proximity sensors, the objects shouldn't necessarily touch the sensor. In order to get a signal, we can work in a range of a few millimeters to a few tens of centimeters. And I'm sure that if you look at any factory that has machines, you will find one of these sensors fixed at some place in order to detect some product or an object moving. Now, capacitive and inductive sensor, especially the proximity one might look really similar from the outside. However, from the inside and from a circuit point of view, they are totally different. The principle of operation is totally different. So starting with capacitive sensors, they are used with any type of object, so you can just put any object in front of them and they will detect it if they are within a certain range that is usually adjustable through a small screw on the proximity sensor. And as I said, the range could be a few millimeters to a few tens of centimeters. And these sensors are digital type. So when an object is detected, you will get a digital output of a rating of 24 volt DC or in rare cases you might find it with a rate of 12 volt DC. Now the inductive sensors, they are only used to detect metallic objects. If you put a plastic object, a wooden object in front of it, it won't detect it and it won't give you any output. They also operate on 24V or 12 volt DC. Now, let's take an example for a capacitive sensor. Let's assume that we have a conveyor band and we have a plastic object moving above it. And the sensor is fixed above this conveyor band. Now, when the sensor is not seeing the plastic object, the sensor is off and it's generating zero volts. Once the sensor is directly looking at the plastic object, the sensor will output 24 volt DC and then we can take this signal and take some action, let's say, inside our PLC program. Now let's take an example for an inductive sensor. Let's say we have food products and food products are sensitive to metallic parts, so you cannot have metallic parts inside your milk, let's say. During a production. You never know where foreigner parts might come in and interfere with your product. So you want to make sure that when this product goes to the customer, it does not have any foreigner parts. One of the methods to detect these parts is to check if there is a metallic part inside this product. So what we do is we put this food product on a conveyor band and it goes under an inductive sensor. If this inductive sensor senses any metallic part, it's gonna output a signal to our PLC or program and say, okay, this product is a problematic ejected out of the system. So this is it for proximity sensors guys. See you in the next tutorial.