 Welcome to today's lecture. This is lecture number 27 under module 7. This means fluidics and fluid logic and the lecture is on basic devices, symbols and circuits. In a fluidic device, a jet of fluid can be deflected by a weaker jet, striking it at the side. This means that fluidic device as already I have told that there is no moving components except the fluid is moving inside. So, imagine a fluid is flowing in a direction and that is being disturbed by another flow from the transfer directions or direction at an angle. This provides non-linear amplification. It is similar to transistor used in electronic digital logic. It is used mostly in environments where electronic digital logic would be unreliable that is systems exposed to high levels of electromagnetic interference, ionizing radiations etcetera. In the field of nanotechnology, fluidics is considered as one of its instruments. I would say in other words, the word nanotechnology is used for various fields. In case of medical science involved with fluid flowing, nowadays it is the fluidics is finding its way that it can be utilized in better ways than any other devices. In this domain, effects such as fluid solid and fluid fluid interface forces are often highly significant. Fluidics devices have also been used for military applications. Some devices are described in brief in this lecture. Now, basic concept of fluid amplifier is described through a patented device as shown in this figure. Now, if you look into this figure that from the bottom, something is flowing through this body. This is basically you can imagine a cavity between two plates, two bodies, there is a cavity inside. Now, what is there? There is a main flow. It is flowing like this. Now, there are at this zone, there are two inputs. You should call this is input, this is some disturbing jet. Now, it is like that when C 1 is being actuated, then flow is moving like this. When C 2 is being actuated, the flow is going like this and it is going through the D 2 and it is going in case of C 1, it will go via D 1. If we consider the pressure, pressure in this directions, usually these devices are of low pressure, even if for the main flow that the disturbing flow is even of much less pressure, but it is the fluid mechanics in which with this disturbance, basically which are normally inaminar flow will be disturbed and it will move in a particular directions. For that, what we need that we need to have some pressure range in these two flow as well as shape of this body. A fluid supply which may be air, the fluid may be air, water or hydraulic fluid. I have described that is entering at the bottom and then pressure applied through this control ports C 1 and C 2 to have the flow in D 1 and D 2 directions. The stream entering the control ports may be much weaker, which I have described than the stream being deflected. So, the device has gain. This means that we normally by this small force, we are deflecting a relatively larger force and that we are getting output through this larger force. So, therefore, we should call it gain in terms of the gain used in both electrical fluid and any control field. Now, with this basic device, the flip flops and other fluidic logic elements also can be constructed. Basic principles remain same. Simple systems of digital logic can thus be built. This means we have already learnt about the digital logic. Now, with this we can make the device which are called gates, different type of gates and with these gates, we can build the logic and we can construct also physical circuits. However, fluidic amplifiers typically have bandwidths in the low kilohertz range. So, system built from them are quite slow compared to electronic devices. That we have to remember. The response will be slow in this case. However, say for example, in many medical instruments, this fluidic devices are used, where it is not required like a computer calculations, but we require much accuracy, safety and hazard free operations. Now, basic device when first it was developed then basic was the triode, sorry this amplifier and then the fluidic triode is an amplification device and that used a fluid to convey the signal. Now, if we look into this history, then the fluidic triodes were used as the final stage in the main public address system in the year 1964 New York Walls Fair. The name of the fair is 1964 New York Walls Fair. Now, surprisingly this fluid triode was invented just two years earlier to this fair by a boy who is Murray Metsy Jr. He was a high school student, but he invented this fluidic triode. Obviously, it is not electronic device, it was some this rather you can say mechanical part along with the fluid parts and he built a fluid diode, a fluid oscillator and a variety of hydraulic circuits, including one that has no electronic counterpart as yet there is no. That means, with fluidics we can make many devices and which may not be available with electronic. On the other hand, there are many things in electronic also which cannot be achieved by fluidics. Now, he was invited in this national science fair and he was also awarded for his project. Now, although much studied in laboratory, then onwards have been done, but there are really few practical applications because to make a particularly to make a circuit although this fluidic devices are very small may not be very big, but in comparison to electronics components it is big. However, at the time when the fluidics was developed the fluidic components were developed that time the there was not much progress in electronic devices. So, fluidic devices where initially was being used for automation and other control system. However, those we are not very quiet we had to many such devices when we are connected together the shape was very large etcetera. And so, it was in many cases it was found that it may not be feasible to use such devices for making a control circuit or logical circuit many accept them to be key elements of nanotechnology. Now, nowadays it is found that which was which did not find its application in general industrial applications or other devices, but it is expected that those will be now will be used in nanotechnology. Now, this is a very simple system is shown imagine a pocket like this it has three holes which is like tube and at the middle position there is a bucket let us consider it is in the vertical positions. You can imagine that a plate is machined like this two plates are machined like this and they are put together in reverse way that means the other plate is the middle image of this and that is put together. So, this means that this is one passage this is another passage this is a cavity inside this is another passage to go out and there is some sort of bucket is placed there. Now, what we can do let us we we can put a ball of diameter is very close to the diameter of the tube not very small neither it is very tight. So, one ball you can it can come through this passage another ball can come through this passage. Now, forget about the probability what may happen these two ball will fall in this bucket or it will fall outside and then through this passage only one ball can go. Now, if one suppose you have sent only one ball. So, this will go out then there will be some function will be performed that one output is there or this ball has come through this then the performance will be there or if the two ball come through this and one by one it is coming out still the performance will be there if nothing is coming out no performance here. On the other hand if these two balls instead of coming over here they take this bucket all that means this two ball fall inside this bucket then there will be another functions. Now, this is just to understand when these two together coming then one function and if any one of them coming through this then another function is being performed. So, this is basically to understand what is or function and what is and function. This is described what I have already told you. Now, logic gates can be built that use water instead of electricity to power the gating function this means in this case the function itself is performed by the fluid flow. This indicates that you may need to amplify this power in case of electronic by electrical devices the power is directly taken from the electrical source. That means whatever is being used for the control that can be magnified that can be amplified and can be used for the power. In this case also we can magnify those, but we have to use the source as a water or other fluid say A M. These are reliant on being positioned in the orientation to perform correctly. This means that you have to make sure that the orientations are correct. And you have to construct the devices accordingly. In case of electrical devices you can say electric flow is through and where you can put in any directions, but in case of a fluidic device you have to careful about this path except where the flexible path can be used flexible tube can be used say for example. And OR gate is simply two pipes being merged a not gate consist of A deflecting a supply stream to produce A bar. Now here instead of going into much little definition of this gates there is a not function. Not function is simply remember because there will be a not function also. Now not function is that simply one function we are reversing that inverse of that function. Suppose A in OR function A means 1 through some input there is a signal output is 1. Now if you would like to make it not 1 then simply you disturb that not allowed to go through that. That means what was going to be output as a 1 you are diverting that then we call inverse of that not of that this means we are this output could be A. Now by applying a disturbance we are getting the output A bar not A that is designated by A bar. So, it is called not gate and inverter could also be implemented with the OR gate this is XOR exist OR as A OR 1 is equal to A bar. The fluidic components appear in some hydraulic and pneumatic systems including some automotive for automatic transmissions. This is just an information as a digital logic has become more accepted in industrial control the role of fluidics in industrial control has declined that means digital logic means electronics logic now it is available. So, you may not find much applications of fluidics in industrial control. Fluidic injection is being researched for thrust vectoring in aircraft jet engine nozzles and for ships. So, only the fluidic principle is being used for fluid injection in case of engines jet engines mainly ships and aircraft. And this is because of that their function is more efficient for less consumption of the fluid sorry less consumption of the fuel and to increase the efficiency. Such systems diverged thrust via fluid effects that means again as I should mention that the we are diverting a thrust by simply we can disturb disturbance fluids which is of mass less pressure. Tests show that air force into a jet engine exhaust stream can deflect thrust up to 15 degrees. So, this is just an information. So, a small jet of very low pressure can divert a thrust into 15 degrees. This means that the thrust is coming if you can divert that that will have better impact on the impeller which will give more power output. Such nozzles are desirable for their lower mass cost up to 50 percent less inertia for faster stronger control response complexity, mechanically simpler no moving parts or surfaces and radar cross sections and slith. Now, this is also used in unmanned aerial vehicles that is UAVS and also advanced fighter aircraft. Now, we shall discuss about a device. Now, in this device this is pneumatic device also the similar fluidic fluid device or hydraulic device can be made, but the this describes precisely a logic gates. Now, look at this. This is the input. Input means as I told a flow that not very high pressure not very high pressure this flow is there. Now, this flow is going through this and then going out in normal conditions when the lever at this position. So, if this flow is there then there is a flow output. So, what we put input 1 output A is also 1. Now, this is being used to perform some some performance. So, it is going to the next device. Now, here I would say that in this case the fluidic devices as I told that it should be have laminar flow even if for the main stream. In this case this disturbance not by the jet, but this disturbance is or we can call it second input that we are moving this lever. While we are moving this lever then this is being closed this fluid is going out that is it is going out to exhaust. If we consider the output here then it is reverse of the output here. So, it is A bar which is is equal to 0. It is not A. This means that by operating this on off on off etcetera we are getting that at either the flow is going to next device or the flow is going to exhaust. So, device is not being operated. So, it this is called the this is basically used in to use as a float. Say for example, water level control in a tank etcetera. Now, the similar function can be achieved by a fluidic amplifier device also. How? Now in this case let us consider this is a large tube and it is blocked here. A small piece of large tube large diameter tube it is blocked here. Now what it is having? Imagine this is a cylindrical body this may be square also rectangular body or square cross section body, but let us it is imagine this is a circular one. Now here there is a small hole. Now in that small hole again a nozzle type small pipe is inserted through which again one flow can enter into this. Now in this case there is no physical connection between this hole to this hole. Simply there is a hole and in this side it may be a tube like this or may not be tube, but the flow of the flow we can consider that supply of this is air P is the pressure and A is the air not P air. Now this flow is a laminar flow it is like that if this flow is allowed through this hole straight way it will go here. You can imagine that as if it is going through tube it is like that. Now when this flow is initiated that means this flow is given then it will be disturbed and it will go through another larger hole it will go out and it will not this flow will not come in this way. So it will not go to next device and the work will not be performed. So this is a basically a hydraulic device this is not a logic device not fluidic device because here is the moving part. In that case there is no moving part except the fluid is moving and this the function is same. Now if you look into this pressure here 34 millibar you can imagine that 34 millibar 1 bar is equal to 0.1 megapascal and millibar means you can imagine this is divided by 10 to the power 3 34 millibar only and whereas this disturbance is 1 millibar minimum of course it can be slightly higher but you need at least 1 millibar and when this disturbance is on this fluid you can see that it is being bent at 12 millibar this pressure is not there. Now as I told this if you would like to use this air source to drive something say for example in that case it needs amplification. Say suppose we need say at least say 340 millibar say that means we have to amplify 10 times that is different issue but 340 millibar air we cannot pass through this to have this performance this is usually low pressure. Now for low pressure pneumatic logic application a turbulent sorry a tubular laminar or turbulence device is a well known fluidic element working on jet interaction principle. This is basically a not or not device it consists of a short tube with two concentric smaller tubes which I have described and this flow is laminar. Now we can have one or more disturbing jet that means in that case say for example this work I mean this will be disturbed either one input or may be either of the one either one of the all the disturbance jet are there or may be two three jet at a time. So this means that this is say in a systems it is like that if one disturbance is there this will not be performed if two three disturbance at a time also there will be no performance only this will be performed it will go to the next device there is no disturbance. So we can make this device multiple input and single output. So this is again I have shown this and the symbol for multiple input it is like that this symbol is used for this device symbolically it shows that any of the control inputs a b c or d can turn the output u of the device to 0 when a or b c or d can turn or b or c or d is or when all of them are equal to one this thing I think here we can put one this means that a b c d any of them is one or all of them one. So long they are all 0 and output u is equal to 1 is available that means only then if they are 0 only then there will be this jet will be will go to the next device and the performance will be achieved. So this is basically a node device the combination of a subtle valve and a three port spool valve may also act as an inverter this I will show that is it can generate node logic functions how now what we have used we have used a subtle valve here and then we have used a another three port spool valve. The inputs a and b this is a and this is b there are two inputs connected to the two subtle valves or in other words a you can call the this is a subtle valve two ends of the subtle valve. So that a is equal to one b is stopped and when b is equal to one a is stopped that means when the flow is coming through this it can go this direction this will be stopped or when the flow is coming from b a will be stopped and flow is going in the directions I mean either a or b this will be operated. If the flow from both side is coming this will be operated also because this valve will be in the intermediate position but there will be passage to go here. So this is basically all functions so either a or b can work in an exclusive way without interfering each other. However the same effect is produced when both a one and b is equal to one the three port three port valve gets a control input and this moves a against the spring and the output from this valve is then 0. This means that if you look into this valve what is there this indicates looking into this symbol this indicates that there is an input flow and it is going out. But when there is an actuation then this will come to this position and the flow will be stopped. So if these are present then there is no function no output function means no output. So that means that either a or b or both of them reverse of that if a is there no output if b is there no output if a and b both are there no output. So symbolically sorry this in equation form we would write like this a is equal to a or b this is plus or b and inverse of that a plus b bar. So this at this point I would like to tell you that actually to remember all such things we need a practice because we are habituated with normal algebra general algebra and this is following Boolean algebra and say suppose if it would follow the general algebra in that case we could have remember easily. But as you see this function is something different we need a practice. Only when a is equal to 0 and b is equal to 0 and output is obtained from this valve hence it is a non-logic system. The conceptual logic gets like and or not and or not etcetera can be fabricated as hardware electrical electronic or fluid operated and when these hardware are suitably interconnected and interfaced many problems of automation can be tackled easily. These arrangements are termed as circuits if such devices are put in sequence with a proper connection between them and we achieve a desired performance then we call it circuit and we call is logic circuit. Now let us see the logic gates and their symbols. Now this symbol is like this it is like a D capital D and look at this symbol carefully one simple line is a capital D and look at is coming this side from left to right and then this is the line with an arrow this we should consider as output whereas this is input. Now what it is doing meaning a ES gate or amplification gate. Now they are a little confusing that ES means a flow is coming in and that flow is going out. Now why we should call it amplifications may not be it is amplified the same input is going out even there might have some loss also drop also but why we should call amplification gate. Amplification gate in a we call it whenever this is not being disturbed and going out we should call this is amplification. Now here we find that the same D but there is a vertical bar in that case a is input and then this will be output is reverse of a. That means if a is 1 say let us consider in that case 1 and 0 suppose if you consider 1 means there is a flow and 0 means there is no flow then suddenly the inverse of no flow must be flow is there. So, it is normally not possible we cannot think of we have not given at flow at all how it can come the output but usually this device is like that there will be flow if there is this flow is not being passed through this only then this is not a think in this way because we are not discussing the internal details of this. Now next one so it is called inverse gate and in this case the first one has no alternative symbol is used but mostly you will find in electrical circuit this type of symbols are used this is called bubble a bubble is used. So, it is not but we can also because this is basically we will call logic circuit say for example we would like to achieve some performance in that case what we should do we should first make the logic circuits then we will think of whether we should go for fluidic device or electronic device. So, you may find also in fluidic device also this type of circuit sometimes are being used. Now next you look at this here input is 2 double input and then output is 2 double is a plus b this plus means or a or b that means if you if there is a signal at a then the output is there if there is signal at b then there is a output both a and b are there there will be output but if a is not there b is not there then only this will be 0 no signal. So, this is this represents or gate or we call it logic sum gate it has also an alternative symbol which is like this usually with this signs there is no arrow is used and remember in usually with all these symbols this a b a plus b etcetera written that means if you do not write this a b a plus b then may be in some cases it might be difficult to understand what is the actual device is because in many cases they look alike not many cases in some cases I would say look alike. Say in this case you see these two look alike but this is for a dot b that means meaning AND gate what is AND gate? Suppose a is there b is not there then this is like in general algebra in that case this output will be 0 if b is there a is not there then is also output is 0 only if a and b both are there then there will be output. So, there is the distinct difference between this and this this is OR gate this is AND gate this is logic sum this is logic product and in this case you will find that alternative symbol has difference this device and this device has difference. So, even if these are not written still you can understand but in this case you have to write to understand this device and also observe here d and this is this also looks like capital D but there is a difference this is this half circle plus straight line here this is normally semi circle or even less some of the logic gates are combined and are given new names which indicate the functional base of combinations that means we have seen OR gate AND gate NOR gate etcetera NOR gate also is there now combining OR and NOT we can make a NOR gate we will we are coming to that. Now here some are shown now let us see the symbols this is OR we have used the alternative symbol OR gate and there is a NOR gate combining this we are getting NOR gate now NOR gate is while we are presenting the NOR gate we have taken this part and we have taken this bubble the intermediate portion is eliminated this means that OR and NOT NOR gate but remember in this device first performance will be OR and then NOT of OR do not be confused it is not like that you can put in other sequence to get NOT device you have to put in this sequence physically you can put OR device and NOT device and gate a NOR AND but the NOR device also can be made separately as we have seen earlier. Now this is also represented as like this usually with this symbols you will find AB A plus B bar is given take another one in this case we have put AND and NOT now this is called NAND but this is not very popular one NAND the same way and alternative one is this if you look into these two these two are again only device looks alike only symbol looks alike but the when we put A plus B bar or A dot B bar that indicates the two different device this is NOR this is NAND. So, these are combining the symbols now another interesting part is that the by De Morgan's theorem what we have learned earlier it follows that if inputs are passed first through NOT gates remember first we are sending through NOT gates in input and then through an OR gate the final output is the same as putting the inputs first through AND gate and then output inverted by NOT gate look at this earlier I told that we if we put NOT and OR we will NOT get NOR to gate a NOR OR and then NOT but if you put NOT and then OR what actually you will get you will get first AND and then NOT this means that you may think of NAND you are getting NOT OR is equal to NAND. So, this using De Morgan's theorem we have already learned and symbolically NAND is equal to bubble to OR say this output we have written here NAND and this can be given bubble to OR what it is input and NOT this input and NOT and then output is OR this is your OR connections. So, we get bubble to OR this is our OR look at the symbols and this is one De Morgan's theorem and also if you take NOR then NOT AND we what we do the reverse way NOT AND AND then OR. So, we get NOR sorry NOT AND AND we get NOR just remember this if you put OR and NOT you will get NOR NOT for both inputs AND OR you will get NAND and vice versa positive and negative logic gave gave rise to basic duality in all identities when changing from one logic system to another 0 becomes 1 and vice versa. So, these are termed as duality. So, just saying this line sentence you may not have feeling at the immediately but if you read it if you learn it you will have this feeling all the plus sign are changed to dot sign or AND gates becomes OR gates and vice versa from this it is called duality. For example, A plus 0 is equal to A has the dual identity A dot 1 is equal to A. Similarly, A plus A bar is equal to 1 has it is equal to A plus A bar is equal to 0. As it has been mentioned already simplification enables and equivalent simpler circuit to be built in place of more complicated one. We have learned about simplification earlier now here something also will be shown. For instance if a logic output is given by Y is equal to A dot C plus A dot B dot C that mean A and C then A and B and C which means an output is available when A and C or A and B and C the input condition are satisfied. The expression can be simplified by Boolean method as follows. Now you see this how we are simplifying this Y is equal to simply you can while you are simplifying you just remember this thing then writing this equation you may omit this dot A C plus A B C. So, simply write it A C plus A B C no harm then this you can take the like an ordinary algebra you can take A C is common. So, this becomes 1 plus B now 1 plus B is a or Boolean algebra and then as there is 1 that means always there is a positive output then B whatever it may be whether it is 0 or 1 it will be always 1. So, this means that this simplification is Boolean algebra you can make simplify to A C. Similarly, another expression if you consider Y is equal to A bar dot B bar dot C bar dot dot C bar plus A dot B C bar plus A bar dot B bar dot C that also can be simplified in this form how you take A bar C bar common here then in that case you will find that B bar plus B is coming over there plus here A bar B bar C. Now this is again this is always suppose this is 1 this is 1 then this is 0 and if this is 0 then this is 1 that means this part is always 1. So, this become A bar C bar and this becomes A bar B bar C bar and that is equal to again A bar C bar B bar C and finally, we get only A bar then C bar C bar B bar C sorry B bar because if suppose C is equal to 1 then C bar will be 0 and whatever the B bar that will be the value there and similarly, if you analyze this 1 this 2 will give the same result. So, this again as I told you it is not easy to grasp immediately you need a practice you have to just 2, 3 times you have to see this housing this simplification is done. Another example is that X dot Y plus A dot B dot C dot into X Y plus A bar plus B bar plus C bar. Now this first you follow the ordinary algebra as I told that you can write X Y plus A B C and X Y plus A bar plus B bar plus C bar does not matter, but remember these 3 items are this separate items A B C not a single item there are 3 items. Remembering this you can write down these equations then you will write into this and finally, you will find this one that means these functions these are you can see so many inputs 1, 2, 3, 4, 5, 5 inputs are there and they are not functions are there that can be simply achieved by X Y 2 inputs and a and function. So, this is becoming X Y now this can be proved by this logic circuit I shall discuss this logic circuits later and this can be simply represented by this one. So, I think we shall continue in the next lecture this one similarly, if we take another example that we will have also the same that first we simplify this U A plus B A plus B A plus B A plus B A plus C is simply can be represented by A plus B C that means, put an input A and then for B C there is a AND gate and then finally, you pass through A OR gate and this circuit as you see that this circuit can be simplified as follows. In that case you see that this A B say if you had to make this function full function in a circuit this will be the circuit A plus B through an OR gate C through an OR gate and A also the same OR gate. So, we are getting this output then these two are this AND gate instead of that use a OR gate here directly put A there B and C through AND gate and then you are getting the output. So, these three devices simplified into two devices one is not required. So, such simplification is required in logic circuits arrived into a simplest circuit. So, we shall discuss in next lecture