 Good morning everybody, I am Roussard Mistry and I will be discussing about ultrasonic rain sensors today. So, the learning outcome for this session are you will list you will be able to list features of ultrasonic rain sensors and you will also be able to animate applications of these ultrasonic rain sensors. Now, from recalling from where we left off we had extensive discussion on what are the different types of rain sensors, what is the definition of rain sensing, how ranging is measured using time of flight and now this is the further conclusion of this particular topic is we discussed one of the most widely used rain sensors, those are ultrasonic rain sensors. And if you can see in the figure on the left, I have one of the most common rain sensors which are available for all laboratory experiments and other sources. And even industrial grade sensors are basically manifestations of these sensors only that is more ruggedized than what we use in the laboratory. So, these sensors typically measure time of flight of a pulse of ultrasonic sound through air or liquid and in order to measure distance, they are available with ranges from a few centimeters to meters and they typically have an analog output which is proportional to the distance of the target. If they are digital, they typically have an onboard ADC which converts the analog signal into the digital signal. We have four of these particular sensors in the lab and these are actually sharp sensors and they are quite good and students have used in the past for various projects and experiments. So, recalling again, how would you measure ultrasonic time of flights? It is similar to any time of life measurement that you can have. So, in this case, a direct source of energy is transmitted by the sensor and it is bounced back from the target and then the range is estimated based on the time of arrival of the signal measured either in the form of phase shift or the intensity of the signal. So, these are the most commonly obviously used techniques for time of flight measurement and the reason obviously ultrasonic sensors typically are used and also time of flight measurement is because it is easy, there is easy availability and these are low cost and these are very easy to interface. That is why ultrasonic rain sensors are one of the most preferred rain sensors from several applications. Then, how does it typically work? So, construction typically includes one ultrasonic transducer and then the ranging module and the electronics. I mentioned this in the past that the range and even the accuracy significantly depends upon the onboard electronic circuitry, the signal processing circuitry. So, not just the transducer which is important in most modern sensors, especially all modern digital sensors and smart sensors, the onboard circuitry is as much important as the quality of the main transducer. The control circuitry activates the transducer, then the receiver is, remember receiver is deactivated for short period of time in order to prevent a false detection due to residual transmit signal which is called as ringing actually. Then the received signals are conditioned and processed to account for noise and attenuation. That is why I say every signal that returns has some sort of an electromagnet noise. Hence, all good ultrasonic sensors as a matter of any sensors will have some sort of signal processing in order to eliminate that noise and give the most accurate reading as possible. So, it is a very simple setup. Let me reiterate that the onboard control circuitry is what clearly defines this sensor. So, whenever you check the specifications of such sensors, apart from transducer specifications, make sure you look at the control circuit specification and give it as much importance as the transducer specifications. Then continuing with obviously the process, the control circuitry activates the transducer like a receiver gets deactivated to prevent false detection and then the received signals are conditioned and processed to account for noise and attenuation. So, that is the process which is used for the measurement operation. Where can you find application of these for our laboratory projects? I just want you to think over it and a hint for you is if you actually have a bought a car recently, then probably you have one. Now, most parking sensors are what typically these sensors. Other than that, see if you can come up with some very classic applications of ultrasonic sensors and see what you can use these particular sensors in laboratory projects. So, when we come back, we will try to have a discussion on applications. Now, continuing from where we left off, remember I mentioned this that if you actually have a car, you probably have an ultrasonic sensor, which is basically a parking assist sensor. So, it is one of the most widely used sensors when it comes to parking assist. The range of applications of ultrasonic sensors is very diverse, it is one of the most widely used sensors and the most common application obviously is object detection. So, object detection in factory automation in robotics is by far one of the most common applications when it comes to ultrasonic sensor. So, in this particular case, the transmitter transmits a signal, signal bounces off a target and then it can detect the presence of an object or the absence of an object. And then it can this part is a part of a larger control system then which can take a decision on what exactly has to be done. So, presence and objects and absence of parts typically is on a moving conveyor for example, is one very classic application of ultrasonic range sensors. The other obviously is to actually estimate the distance, we say it is a range sensor. So, one of the obvious application is actually to measure the range of an range of an object. Now, in ultrasonic applications, we typically use sound pairs in the ultrasonic frequency range and it is this is preferred you have to understand because the circuitry is significantly simple for sound as compared to light. Sound travels at a speed which is several, several times less than that of light, 3, lakh or 300,000 kilometers per second as against let us say 340 meters per second. So, the thing with sound based systems is you can get a very high resolution when in very with reasonable you can say electronic sophistication. If you are looking at any light bit application, the level of sophistication is just several times more than what you can expect in any sound based application. And that is why it is one of the most widely remember, but this is, but the range here is very limited in most applications the range is not more than several meters. So, it is few millimeters to a few meters this typically the range when it comes to ultrasonic. Sound was obviously larger, but ultrasonic is typically limited to a few meters. So, measuring distance is like I said one of the major applications for ultrasonic range sensing. I mentioned this before the applications are actually tremendous like there is this there can be an entire session on what the applications of range sensors are. So, if you have to just do a summary of this in mobile robotics typically position estimation is what you use ultrasonic range sensors for. So, this is actually used in localization and if you do not have a global system of localization then ultrasonic sensors can be used to in order to estimate the position of the robot in terms of some sort of a local quality. Collision avoidance is again a very very widely used you can say application of ultrasonic range sensors. And this is not just in mobile robotics it is used in other in vehicles and automobiles as well today. And mobile robotics you can say is the first case where collision avoidance was introduced and ultrasonic range sensors are significantly better than say infrared range sensors when it comes to collision avoidance. So, this found wide application in automation, automobile and logistic applications. Another this thing is motion detection in security systems which typically are used in homes nowadays. They are typically either passive infrared and an alternative transduction obviously here is ultrasonic sensor. And these will detect motion of objects and then a security alarm can be set up if some let us say an intruder is detected. So, that is where typically an application of ultrasonic range sensors. But let me carry you in motion detection especially security systems passive infrared are preferred over ultrasonic range sensors whereas in industrial automation obviously we prefer ultrasonic range sensors. Then other industrial application like as I said collision detection like the various you can say collision detection is a very generic term the same concept can be actually used to measure level or depth. So, ultrasonic range sensors have been used extensively to measure level or depth especially non-contact type. If you are using contact type then a potential metric arrangement through a lever arrangement can be used. But otherwise even depth measurement and level measurement in wide range of process engineering ultrasonic range sensors find application. And these typically include like even in paper print industry like if I have to analyze industrial domains then they find application in paper and print in textile industries plastics packages and metal working in order to identify gaps between two parts. And there are several applications like I mentioned for ultrasonic sensor. Coming back again to automobile I mentioned your parking assist is one of the classic example that you can find for ultrasonic range sensors. Especially in the rear bumper there will be at least four sensors you can add to it by adding a camera but parking sensors can get the job done. So, they will estimate the distance of that particular object and then they will give some sort of an auditory warning which increases in frequency as you approach that particular object. So, here one question arises should we call them as rain sensors or proximity sensors. They do detect proximity but this sense it is not a fixed threshold and they do estimate the range of that object to a certain level it is fair enough to classify them as rain sensors as well. Collagen detection is also one application that will come in automotive that in cars in order to estimate the distance of a car which is in front of you. So, that is one application of rain sensors which is going to be the case. It also will be used to range the distance of the car which is in front so that you can maintain a certain distance of your car from the other car. And it is going to find extensive application when it comes to autonomous driving. Defense obviously is one area where ultrasonic sensors find wired applications. And I definitely urge that you read the mechatronics handbook by Bishop as a dedicated chapter for sensors and it is definitely a worth read. For some introductory information about the same mechatronics by Bolton, introduction to mechatronics by Bolton is also a very good read. Chapter 2 is dedicated obviously to sensors over here. Thank you. We will continue with the discussion on other types of sensors in the next session.