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Module 1: Product Functions

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Laboratory Exercise: Electrical Cooker and Kettle

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Laboratory Exercise: Electrical Cooker and KettleWelcome to the fifth laboratory session. So, in the last few classes, we saw how to doa systematic dissection of a product and identify the parts and then prepare a parts listas well as the assembly chart of a product for a product and the technical assistants arehelping you to do this task. And I hope now you are familiar with how to do the firstpart of the dissection process where you do in a systematic way of opening theproduct, identify the parts and subassemblies and then looking at the functions ofthese parts.Now today we will be looking at a different product. This product is going to be theelectric kettle and a rice cooker. We will be doing two products, an electric ricecooker and an electric kettle. Both of them have some kind of common things that iswhy we club these two together. You will be looking at these two products, doing theproduct dissection. At the same time, you will be practicing a theoretical concept thatwe learned in the class, which is how to prepare the needs list for a product.Looking at the customer requirements, how do you identify the customer needs andthen prepare a list of needs based on the priority of the needs. During the theory class,we saw how to conduct a proper need identification exercise using Like/Dislikemethods and then doing a sorting of the needs, using the affinity diagram and thenfinally coming to the list of needs for a product.In this case also, we will be going for the preparation of needs list by following theprocedure that we already learned of getting the needs identified. So, the product thatwe are going to use is an electric rice cooker and electric kettle.(Refer Slide Time: 2:14)The objective of this exercise is to understand the function of the product and identifyall the parts in subassemblies and prepare the parts list in the assembly chart, which iscommon for all the exercises. Now in this exercise, what we will be doing differentfrom the previous exercise is the carrying out the Like/Dislike method of needidentification.You know how to do this, need identification using Like/Dislike method. We haveseen a few examples in the theory class. So, each one of you will be having a formatfor the need Like/Dislike method. Then you write down your likes and dislikes andthen convert that into interpreted needs and then prepare a needs list.Each one of you will be having a set of needs. As a group, you sort out these needsusing the affinity diagram method and finally come up with the needs list with thepriority. That is what is expected from you as part of this exercise or outcome of thisexercise. One of the products we will be using is the electric rice cooker. Most of youmight have seen this product. It is a very simple product.There are not many complex mechanisms or systems inside. It is a very simpleproduct with electric modules for heating and sensors and some switches for cut off ofthe electricity based on the status of the process going on.(Refer Slide Time: 3:48)The product is an electric rice cooker, and the primary principle is based on the factthat water contains constant temperature while boiling. The TA will explain theworking principle to you. When there is water inside, the temperature will be alwaysconstant and when the water is completely drained, then the temperature will startincreasing and when the temperature starts increasing, the system will cut off thepower supply. The rice is already cooked.That is the basic principle. So, you will be looking at the electronics and the heating,what is happening inside the product that will be able to see and the TA will explainto you the functioning of different elements.(Refer Slide Time: 4:31)The major function of the product is to cook the rice and to achieve that one, you needto have many functions in the product. One is basically just being able to contain riceand water. You should be able to have the rice and water inside the product that iscontaining the elements, the materials, rice and water, and then it has to generate heat.And at the same time, you need to have control of heating also. So that it does notovercook or it would not get burnt. That is why you need to have control of heating.So, these are the main 3 functions we can say.Then you need to see how these functions are achieved through the different elementsin the product, so you will be able to see the generic diagram need not be the same asin the product that you are using, but generally there will be a heating element. Therewill be a circuitry which actually measures the temperature through a sensor. Andthen using this data is used for cutting off the power supply or to stop the heatingprocess. So, that is basically what is there in the product.So, the procedure is the first 4, this technical questioning and mission statement is notnecessary. We will not be doing the technical questioning and mission statement inthis case. But what you will be doing here is the Like/Dislike methods, Method ofneed identification. You need to identify the needs of this product, suppose you aregoing to redesign this product, if you are going to redesign this product, or you findthat there is some problem with this product.How will you identify the needs of the customer for this product? That is basically theneed identification. You use the Like/Dislike method of need identification that likedislike formats are available. So, use this format and identify all the needs and thenuse the affinity diagram method to sort out the needs and then get the needs list as anoutcome. You need to prepare the needs list. So, the report should contain the needslist apart from the other details asked for in the reports, I hope you understood this.(Refer Slide Time: 6:58)So, the report format, the first part will be the same as in the previous cases. But thedifference will be the assembly chart. You need to have a need identification byLike/Dislike method. So, you need to show the format you use for the Like/Dislikemethod of need identification and then getting other interpreted needs and then howthe interpreter needs are sorted out to get the top needs of the product and thenprovide a needs list.Once you prepare the needs list your exercise is complete. So, the TA will help you tolook at the product and product’s technical details. And after that, as a group, youneed to look at the product and then find out what kind of needs will be there for thecustomer and then how do you sort out the customer needs and then get the needs list.I hope you understood this. You can go to the TA and then the TA will help you withthe experiment.TA: Do you know the concept of bimetallic strips? So, there are 2 metallic strips ofdifferent melting points, when the melting point is reached by one and the other doesnot actually reach the melting point and there is a bending of one strip while the otherexpands. So, have you come across a thermostat? So, it follows the same concept.So, we are going to look into two products today both working on similar principles,but the sensor is going to be different. Here we are going to use something called as aFerrite thermostat and here we will be having the bimetallic strip, but both of themwork on the same principle that detection of heat, the current, which is going to passthrough the coil will heat the coil due to resistance offered.(Refer Slide Time: 9:09)We will start dissecting the electric cooker today. So, let us start with the parts. This isthe metal lid and we have the next part, which is a hot pan and it has a sieve. So, themetal pan is anodized, so that there is an equal distribution of heat. And why do wehave the sieve, just to avoid the rice getting stuck to the base of the pan. You need notonly cook rice with your automatic cooker. It also can cook your normal vegetables.So, what is the process of rice cooking? There is this four process, 4 steps, of cookingrice. The first step is that you are going to add water, rice, there is going to be anincrease in the temperature due to heating the coil, rice absorbs water and getscooked. Now there is no water inside the pan. What happens? Will the temperatureremain the same? Why does it get burnt, correct, why does it get burnt?Don’t you feel there is an increase in the temperature than the actual? What is theboiling point of water? 100 o C. Does this remain the same at all altitudes? No. So, youhave to choose a sensor which works perfectly for higher altitudes at sea level andbelow sea level. Let us look into the other parts also. If you are able to see. The coil isactually inside this heating base. Now, let us dissect, keep the screw safely. It is thebase of the pan and it has all the ratings of these electric cookers.(Refer Slide Time: 10:35)So, by ratings, what do I mean here exactly? Voltage ratings and power ratings. So, ifyou see closely there is 230 Volts and 50 Hertz rating, what does that mean? So, is…is the same when you go to the US, if you are going to develop a product which isgoing to be of 230 Volts 50 Hertz and use the same abroad. Will that work? What doyou need? You need an adaptor.So, the point is you should be able to understand the standards of the market andwhere you are going to apply the product. The next that we will be looking at is thepower cord. So, the power cord, what actually is happening is you are connecting tothe power. It is being connected to the heating coil that we saw. We spoke about it.We will be dissecting it and removing it out. So, for now you are able to see that it isconnected to the heating coil and you are also able to see a limiting switch.(Refer Slide Time: 11:28)So, this will be placed here, which is going to be attached to the switch, you’re on andoff switch. There is basically a lever mechanism. Once you switch this on, it isconnected to the thermostat, which is inside and the heating begins once the heatingcomes to a point above a 100 o C, assume, it is the metal lever, which is in thethermostat it is going to release. And this push button that we have switched on willalso release. As a result, power is cut off. Do you follow? We need not set thetemperature. The temperature isStudent: Predetermined.TA: Yes, not the surroundings, the thermostat. So, the one the portion that you seehere. It is going to be based on the material of the thermostat this is called as what weuse here is a ferrite thermostat. I will be telling in deep about it… so about this and.So, this your power cord with two wires connecting to the heating coil and one to thelimiting switch.See, this is your heating base and this is the thermostat. If you are able to see there is ametal lever to the thermostat, this is where you are going to connect the power cord.The cup and heating coil is anodized so that there is an equal distribution of heat.Now this is for spreading heat also. So, here is where the actual heating up starts andit is going to spread throughout here is where you fill the heat. Let us also remove thisthermostat.The working principle of this Ferrite thermostat, I will be explaining. If you are ableto see this metal lever here, the metal lever gets attached to the magnet inside it. So,here is the actual magnet. And this is the metal lever. What happens is, once the100 o C, once I switch it on once this lever, once I am going to switch this on, it tries topush it down. And the metal lever which is attached to this end, attaches to themagnet. Have you heard about para magnetism?So, a normal material at Curie point will transform into a paramagnetic metal. So, at100 o C, this metal lever becomes paramagnetic, detaches itself from the magnet andtries to push it off, which means it is trying to cut the contact from power, understood.That is the working of the Ferrite thermostat. Let us dissect this also.The advantage here is the complete lever mechanism, which is going to automaticallyswitch it off. So, if you come up with another method, or another thermostat oranother sensor to do this using another mechanism, not probably the lever mechanism.So, whichever is less costly, it has to be cost effective first. Correct? And also it has toabide by the 100 o C. You are able to follow. It is inside.(Refer Slide Time: 13:14)So, basically this metal lever, which is the switch here, this on off switch, it is beingconnected to this end of the metal lever. Once you switch it on, it gets attached,everything is in contact with the power supply. So, what happens is 100 o C is reachedand the curve point of the metal lever behaves like a paramagnetic metal and itdetaches itself. As a result, there is a switch off and a cut off from all of this is alsopart of the thermostat so I want this as a separate subsystem or a subassembly.Let us now remove the other. So, you’re on and off, and you have no indicator LEDwhich will be placed and the other end these two ends will be connected to power,this is ground, that is an indication of looking, is there an LED mode, is there a lightin mode. So, this is your switch, metal lever on and off. And then you have a simplecolor coded strip to show whether it is cooking mode or not cooking mode.What other modes. So, what other modes can you think of in an automatic cooker?What other modes would you want that just provides you with warming the food? So,you have only one pan here. How would you add compartments? Can someone tellme the working of this electrical cooker working principle?Student: So, we press this lever, lever then locks the Ferrite thermostat into onposition which is then fixed to the magnet hence completing the circuit. Now thecurrent passes through a heating coil, because of existence, it builds up heat then thisheat is transferred to the heating pad and thereby increasing the temperature in thewater or cooking substance.TA: Once it is cooked, what happens?Student: Then when it becomes sufficiently heated, then the magnet or the lever thatwe locked into the magnet, it will become paramagnetic and detaches from the.TA: What is the point?Student: 100 o C.TA: It is called the Curie point.Student: Curie point yeah. When it reaches the Curie point of the material, then itbecomes paramagnetic and hence the current gets disconnected.TA: The leverStudent: The lever, lever gets disconnected.TA: You are able to see in this metal lid there is a hole, you are able to absorb. So,have you seen a pressure cooker? How do you compare this pressure cooker and ourelectric cooker? Even if there is a blockage that is why we are providing an extraspacing on the sides. To prevent pressure build-up.TA: No, that is what. See the side holes and there is an opening here. These are allsafety concerns. The complete water gets absorbed. So, once the complete water getsabsorbed is when your actual temperature rises. So, if you are going to add excesswater, then there is a problem. There are specific measures as to how much rice andhow much water should be added for an automatic cooker, which is different fromthat of a pressure cooker, different from that of a normal cooker.Moving on to the next product. This is our electric kettle. I would not mention it as awater kettle. What else can we do with this?Student: Boil water.TA: Boil water, stored water. So do you guys not cook anything with the kettle? So,if you are able to actually see the coil inside is open here, can you cook Maggi in this,can you cook Maggi in this. So, what happens when the coil heating coil is in directcontact with water and it is being at a surface below. So, this is your support bracket.Support bracket for the switch.Here is the actual switch on and off that we do. It is connected to a lever again. Andhere if you are able to see, we have a coil, this is the one socket, support base whichconnects to the power base. Once the jar sits on the power base, it comes in contactwith the. So, it comes in contact with the power cord and automatically heatingbegins. What is the principle of heating that we are using here?Student: Joule’s heating.(Refer Slide Time: 23:30)
TA: This is a support base here. We have this switch we will be able to remove theswitch also. So, this is a switch. And we have a light indicator which will be presentbelow the switch, the switch is connected to the lever that goes up or down, and it isconnected to this one. The other end of this lever is connected to a bimetallic strip. So,this bimetallic strip is placed exactly beneath this smoke tube or the not smoke,vapour chamber or steam tube.Once water starts heating, the steam gets into the steam tube and this bimetallic stripwhich is placed in direct contact with the steam tube is going to be heated up. Onceheating is detected, the strip melts and if you are able to watch. Ok. So, we are,switching it on, once the heating or the steam comes in contact with the bimetallicstrip. What happens is it melts and it opens.So, once this switch is open, again, the same concept power is cut off and you cannotheat it up until some period have you noticed that. So, exactly you have to think likethat. So, where can you compensate for all these components?TA: There was a separate LED indicator to show whether it is connected to power ornot if there is so but the point is for you to just have the heating. So, this is the washer,no… not some here from the water. If it is not properly grounded and if there iscurrent passing through the heating coil there are two designs one with direct contactone. So, what do you think?Here if you see the heating coil is being connected to this washer separates water,which is on this site, and here it is going to be connected to the power cord. It will besitting like this. Basically it sits like this without your water kettle. If you see this isthe actual structure. So, if you are able to cover this up and provide a passage for heatto actually go into this water flask, what would it be? What kind of designs would youcome up with? Metal base should not pass the heat as and how much it gets. So, if it isin direct contact.Student: Washer.TA: So, washer is a problem. So, one thing that you are suggesting is to provide abetter washer size and the other one is to completely lock it out from water. Correct?So, why do we have such a complicated design for the heating coil?Student: It cannot be bigger than this?TA: So, how would you change the mechanism? So, that comes in direct contact withthis heating coil.Student: This is for steam, right?TA: This is for steam. This comes in contact with your heating coil.Student: Why two strips?TA: If it is open, if your lid is open, then the steam will not enter directly here. Now,this has to add. So, I want to ask a question, why this model of heating coil, why can'tit just be a plain, circular?Student: Increased area of contact.TA: More area of contact. So?Student: So, it heats better.TA: So, if you are going to I just have a question. So, if you are going to placeresistors in series and resistors in parallel, which would provide more heat, more heat.Student: Series.TA: What is the equation in terms of V because here you’re I varies, V is constant.Student: Parallel.TA: So your parallel connection has better heating than your series connection, fine.So, if you are going to alter the heating coil design what better can you suggest. So, ifyou see it is like protruding if you are going to place it inside a compartment, should itbe like this or you need some other model?TA: So, you have to increase the number of coils probably.Student: Spiral may work.TA: Spiral.Student: Mesh.TA: Mesh. So, if you are having a mesh and you should also understand that it isgoing to heat. Will it be able to hold that much of the heat?TA: So, think about the designs. It can be a coil.Student: Expanding coil.TA: Yes. You did not see any facility for it to expand, right. It was just a washer. So,probably you could think of this, if it is going to expand what would happen.Student: It could break.TA: Exactly. So, do you need that much heating to happen? Cannot you go in for ametal, which is going to accommodate all of this because we are just going to heatwater? You are thinking of… okay. So it goes in with your uses also. I am not able toget you.Student: This is an old model.TA: Can you see the name. This is Usha. Yes, the middle name is given here, this isek612. So, we will also open up this. So, can you open it up so open this? It will besitting over the heat base, so it is supposed to come in contact with this, whateverprotrusions you are able to see here, will come in contact with the power cord. So, wewill open that. Can you open it? So, you can see the bimetallic strip.Student: Slide touch.TA: Yes, it is supposed to detect. So, it basically depends upon the material or yourbimetallic strip. So, your sensor has to be effective enough to detect a change intemperature.Student: Small amount of heat?TA: No, not a small amount of heat. That is what so it has to be with a melting point,boiling point of water? So, yes, the washer will go in the separation to places. Place itlike this. This comes in and then you place.So, this is the power supply connection. And here your switch will, lead indicator willbe placed here and the switch comes in, this is your filter and you can see the steamtube here. It is open, the coil is open, right? So, that is open. So, if you see this is thepower cord. You have to plus, minus and ground. So, what. You are able to see.So, when you place your pan on top of this automatically this will open up and it getsexposed and this is just a simple spring mechanism. So, you should be able toappreciate the little, little designs that they have put in, okay. So, this is not powered.What if it is not close.Student: Anyone can come in contact.TA: You can touch it even when it is not on? Yes you can. See no it is not all the timethat I mean adults use it. So, what if children are there. No, this is not a switch. This isjust a power cord, which is going to be connected, and once you connect it to youractual sitting base, it will provide power the switch is different. Here is your actualswitch. So, have you taken enough pictures?Student: Can the coil be placed in a different compartment?TA: Yes, so that should be one of your design improvements. So, when you place it ina different compartment and you place it in direct contact with water the design isgoing to change and whatever the mechanisms involved in this direct contact of awater kettle is going to be different from that of a non-contact water kettle. That ishow the current water kettles. Have you seen another version of this water kettle…not this new one.TA: So, it will be open and you just have to place it on top.TA: So, there the opening or closing whatever comes in, it will come along with thecoil. Instead of placing the coil with the.Student: So, can you keep the water warm?TA: Here it cuts off at 100 once it starts boiling, it cuts off. So, if you want to keep itwarm, you have to add another mode. So, have you heard of fuzzy logic concepts,fuzzy logic, so can you incorporate any of your warm mode, hot mode? Can youexplain? So, it is basically like a condition where you assign a parameter to a set ofvalues it need not be either 0 or 1. It can take any value between 0 and 1 and you canassign a state to it. So, if in case you take 0 to be your off mode on to be your full Imean, say cook mode in between is your warm mode so you can incorporate anynumber of logics into this and create your other modes without actually incorporatinganother mechanism, mechanical point of view. In spite of that, you can just add inlogic and create a separate circuitry to provide the heat that you actually want. So,what if you reduce the amount of current that is actually passing through?Student: Because the water is as such heating, adding another circuit might help.TA: Yes, you should.TA: So, start assembling the product. Any questions? Yes. Whoever is in directcontact has more heating than the top layer. So, if you want to make it, we have aquestion guys, if you want to provide equal heating like throughout the, I mean waterwhich is present in the can.Student: Maybe the vessel can be changed.TA: What else can happen?Student: Maybe the vessel can be more on the base.TA: So, if you are going to change the design so as to go.Student: Change the material of the case.TA: Exactly if you are going to change the container metal to an anodized one so thatit provides even distribution of heat. Instead of going for a vertical heating.Student: Why should we anodize?TA: No that is base. This is basic. Anodize for just providing equal amounts of heat orequal distribution. See it is you are going to coat something. The coating that you aredoing is a material. Yes, it is a material which provides an even distribution of heat.Yes, no this is a model. This is a model. It will be. So, what you see here is ananodized pan. This is an anodized pan. The rest of the material is just metal. This isbasically a sieve.Student: Where do you place it?TA: Below water. Ok. Assembled? Any questions on this product. So, for the designimprovement, what all we discussed.Student: Coil.TA: Direct contact of the heating coil. Other one was?Student: Change material.TA: Material. So, we can go in for metal. If we are going for a metal, would it costmore, less?Student: More.TA: It costs more. So, that is also a factor. Third. We talked about even distribution ofheat. So, if… if the coil is going to be vertical or coating of the entire inner layer. So,one other thing that you spoke of was to store the water and keep it in warm mode.So, any other additions that you want to make? Moisture, washer. Open, supportbracket, button and here we are fixing back the support bracket. And here we will beplacing this entire thing. So, your product actually consists of your water and it alsohas an indicator for how much water. It should not go above this value. So, what is thecapacity of this? So, what happens if you can, if you go above this limit?Student: Water will spill.TA: Spillage.Student: Doesn’t get heated.TA: Okay. So, the whole point of equal… equal heating does not happen it actuallygoes one layer to one layer, right. So, this is a maximum limit of 1.2LStudent: The coil is present below, what is the advantage?TA: Coil below. One is there is no direct contact. And you are trying to place theheating coil below that is actual. And also the… the consumption of heat from the coilhappens from below. They are not trying, they are not trying to replace this wholeheating coil problem. They are just trying to place it not in contact. So, there is less.No, uniform heating happens only with a material which is going to be completelyanodized. So, if you are going for a steel water kettle. Any questions?Student: Is it for this?TA: This is just an add-on to it. Is there a compartment? You want it open. So, shallwe go in for the discussion? So, for this lab, we saw two products. One is theautomatic cooker, automatic electrical cooker, and the other one is your automaticelectric kit, or your electric kettle. And you can also, here this product is going to bejust cooking mode on and off mode the same way as this electric kettle, which hasdirect contact with the heating coil, is going to switch on. And once the water boils itis going to switch off. These two are what we looked at today.Thank you.