How about the point the thing about signs point to Jaden Daniels and the commanders? Weren't there reports that their meeting didn't go so well? They're face to face with Daniels and the Redskins and didn't Daniels send out smoke signals about Wine to be elsewhere like maybe even here? I know that he was not the most impressive quarterback of the combine. That's probably where the face to face meeting was if not the pro day, but he's also coming to Washington this week. So they're going to have another face to face meeting probably an overnight like he had here. That's what we're building. We're going to draw out plays. How do you react to this? That's the most important meeting. So we'll see. I believe Schefter. The most important thing I heard there, though, wasn't signs point to where it's expected. It's we stand by it. He can't go back on that now. He said it twice and reminded you the second time this is where we stand. Yeah, I think the other thing with Schefter is he says unlikely that the Patriots would move out of that position. And I think what he's trying to say is not that the Patriots are going to move out of that position, but when you trade down where you're going and if you go down to where the Raiders are, do you have a player in mind that you still like when you get to that spot, when you get to the Raiders spot is there a quarterback specifically that you still think is worth drafting because you trade that away already. You already talked about Caleb Williams is gone. Jane Daniels is gone that whoever is in that three spot is either McCarthy or it's Drake May is gone. And by the time you pick at three, who wasn't picked at three is going to be gone too. So do you love bow nicks? Do you love Michael Pinnocks as much as Michael Felger does? And so maybe that's why they're reluctant to trade. They're open to trading, but it's going to be the right partner. Maybe the Raiders are the wrong partner. And that's too far back for me. I mean, it's also the equity you're getting back. What are the other picks because we talk about, oh, you get three first round picks. One is the one you get when you move back nine spots.  Marvin Harrison Jr. Roma Dunze, Joe All, Olufashanu, like all of the best receivers, tackles are going to be gone before that. By thirteen? Yeah, I think so. All those quarterbacks, all those receivers, all those tackles are gone at thirteen? That's the type of draft it is. Those are the type of needs that those teams have in that range. And if you're the Patriots, it's deep at receiver and offensive tackle. But if you're the Patriots, it's more than worth my while. If I want to trade back, I'm looking at seven or eight or maybe nine. Okay. Let's get to what you wrote last week because it's it's germane. So last week, the J. J. McCarthy rumors sort of get up to the Patriots. Okay, so here. Listen, the rumors picked up last week at which point Andrew Callahan basically went in the Herald and said fake news and said people who did that are making it up. People who are doing that are bored. The words are on this paper. You know what? That's not what's in front of me. Basically, I'll just summarize. If you're saying J. J. McCarthy to the Patriots, then you're making it up or you're bored because it's silly season. Now I ask you, Michael Holly, among many other reputable reporters have come out and said J. J. McCarthy to the Patriots is a very real proposition.  I never said they're making it up. I said it's inseparable. You can read the quotes. They're on the paper. They were on the teleprompter. It's a silly season. It's silly season, but in that same column I said this could be a possibility. It's just a new possibility that we've only heard about in silly season. This is a guy we've all regarded on the media side, granted. To be outside of the top 15, top 20 players in this entire draft, someone who's not worthy of a top three pick. I am positive that the NFL thinks highly of McCarthy the way that he plays, the way that he won, even though this is a team sport, and the way he And I'm a little bit higher on him, honestly, than I was eight, nine days ago with that column. Now, why is that? Why? I watched every single throw. I watched every single run. And when you look at the whole totality, the picture, which the first column I had written after four or five games, watching their totality, this was all cut-ups now since then. He makes every single throw, and he operates over the middle of the field better than I thought. And that was what was separating him from May, from Jane Daniels, and certainly Caleb Williams, in my mind earlier. All right. So, would you be shocked if the Patriots, if the Patriots don't trade out? They, number three, they say, we got Drake May or J.J. McCarthy. No, we're taking McCarthy. That's our guy. Would you be shocked? And would that be the right move? So you're, you're, this is your fault. You're contributing to this. You've said it. Mike Giardia said it. Others have come forth, said they really like him. But Tony Pauline. I don't like him. It was comment. I don't like him. But I don't like him. But I know, I know they do. Reputable people had said they like him. To me, it would be a disappointment. I said it when we did that first show nine days ago, and I came on and talked about that same column. I'll say it again now. There is a gulf in my mind between May and McCarthy and their NFL potential and the prospects they are now. It would be, it would be a mistake. Okay. And would it be a mistake for the wrong reasons? Meaning, is that- Possibly, yes. You know, it's not just straight up, we think this guy's better. We think he's safer. Yes. Or he's more coachable. Or it's something like that. Do you think it would be done for the wrong reasons? Yeah, possibly.  He won in prep school. He won in Michigan. Out of every single game that he stepped on the field last year, he had the better team. That's not going to be the case here in New England for your first two, three, four years. The other part is, if he's a safe pick, maybe for someone who's in a contract here in Elliott Wolff, who in his first free agency didn't spend a ton of his boss's money, wise move if you want to keep your job, and Elliott's confident that he'll keep this. To me, I don't want to make the scared pick. You're at three. You don't want to be here again. Take the guy with the best upside who can be and win the way that the best quarterbacks are. It's not McCarthy. Here's what I really want to ask you off that column last week. That if people are making it up, or if teams are just throwing out misdirection, which is obviously possible. I don't know. Especially at the time of year. Okay. At the time of year, teams throw out trial balloons and misdirection all the time. So let's say the Patriots are fueling this hype on J.J. McCarthy. Why? To what end? What do they try? What do they want to happen to get teams to bite on J.J. McCarthy? Who do they want to bite on J.J. McCarthy and why? Well, this noise, let's call it that, or some mixed reporting comes after the Vikings moved up to 11. J.J. McCarthy fits the mold of a Shanahan quarterback, plays on time, makes short throws, is going to plug in the system, make everything else work. He'll take the check downs. If Minnesota really loves McCarthy as opposed to Jaden Daniels, and they expect Kayla Williams to go one, then Drake may to go two, and it's McCarthy and Daniels, and they know that team who just traded up. Obviously, if her quarterback likes one of the two guys, we'll send out all the signals. If you want to come get us at three, first of all, we're going to take your guy. And second of all, it's going to cost you, as I said, to go first round. But that means the Patriots don't want any of the top four guys. That's what that means, then. If what you're saying is right. Or they look at this and say, we'll take Jaden Daniels up until the point we might get an offer for four first round picks. I think they're trying to create more options for themselves. Which means they can live without Jaden Daniels. They can live without some of that. Right. That's what that means. And you're right, because the question is, where's the cutoff, though? Where's the cutoff? Well, no, no, no, no, no, no. If you think Jaden Daniels is Patrick Mahomes, you don't take any offer. So if you're willing to take four but not three, I mean, you still don't really think he's like, if you think he's the guy, there is no offer. Well, there's a difference between the guy and a guy you can win with. Like Caleb Williams has been the Patrick Mahomes, which is always overstated. Mahomes is a one-on-one. Might be the greatest quarterback ever. But if you think Jaden Daniels is the top five guy, you're right. Take him. They might just go, we think he's top 10 or 12. Let me answer it. Because, again, everyone has a price. I asked this on the radio today and Maz gave me the simple answer, which is right in front of our face. Let's say the Patriots really want Drake May. Drake May is their guy. Yes. They're calling the JJ McCarthy hype to get the dumb commanders to take JJ McCarthy. So Drake May is left for them at three. Like that would be a reason to do it. Except, except you don't have to work that hard because the commanders are either going to take Jaden Daniels or, or McCarthy, if they want May, you say the Patriots really like May. Yeah. The Patriots really like May. They're going to get them. May will be there at three. I think it's either for the commanders, it's either McCarthy or Daniels. Do you know this or do you think this? At two. I think it. I love it. I love it. I love it. I love it. I love it. I love it.


West Asia and the Horn of Africa. Two regions which over the past few years have seen intensifying conflicts. Two regions in which the United States of America continues to play a crucial role. And two regions which have seen major developments in the past week. We'll be discussing both on this episode of Mapping Fault Lines. We're joined by Prabir Prukayastha. Prabir will start with West Asia, specifically Israel, where after years of political chaos, the fifth election taking place in close to four years, and this time it looks like he is back with a majority which might be quite low by our standards of other countries, but which by Israeli standards is a good enough majority to be in power for quite some time. Now, of course, he's also come at the head of a government which is likely to be even more right-wing than his previous governments. So, first of all, could you take us through what these elections right now tell us about the situation and the political context of Israel right now? Well, there are two significant things that have happened in this election. I'm leaving out Netanyahu coming back after all the charges of corruption, etc., that he has had. I think the two important parts is whatever little left forces existed in Israel and also Arab voice, both seems to have been almost marginalized completely as a result of the selections. So, they're now going to be there in the parliament because they haven't crossed the 3.5% threshold that is there and therefore they don't have it. They're now going to be there represented. In fact, that's also why this swing to the right becomes even more important. The second part of it which you, I think, are also referring to is that there is an openly right-wing party which has advocated that the Palestinian population should have no rights, that they should have no political rights. If they disagree, then it should be forcibly deported. In fact, the argument was that it should be a completely Jewish state and the Palestinian population should actually be forced to leave Israel. This was what Meir Kahane, the original founder of this ideology represented, forcefully throwing out of the Palestinian population and make the Jewish only land. This is the strand that has come into the parliament this time and this is what Netanyahu has allied with openly. Now, why should it surprise people in the world? Because we all regard Netanyahu as a right-wing in any case. We also regard the bulk of the political parties now in Israel, essentially arguing for very little rights for the Palestinian people and slowly disenfranchising them in various ways. Here, the difference is that it is officially doing so. It is doing so with the sanction, apparently, of religion because they are arguing this is what is there in our religion and the texts call for this. It is really the Old Testament, i for an i, tooth for a tooth and also who should be considered human beings and who are not really fit to be called human beings. All this unfortunately is there in the religious texts of that time. But don't forget it's more than 2000 years old. So, those are the things which are being espoused today and of course there is a serious problem with that. So, when you look at the right-wing which is Netanyahu, then it is quote-unquote a secular right-wing if you will. The ethnicity is the identity issue. Of course, it's a Jewish identity, Jewish majoritarian outlook, all of that is there. But it is not referring to all its practices from, say, the Old Testament. And that's what makes a difference from what is identified in Israel as a religious right, which is what this is. Don't forget, we had Baruch Goldstein, a follower of Meir Kahane who openly killed a number of Palestinian people and essentially justified it. That was the strand that this is what we have to do, kill these people, exterminate them. That was the message that came through. And also the fact that the person who is leading this party, Itamar Ben-Gorir, he has also been a great fan of Goldstein and of course, Meir Kahane. This is the strand which has come openly to power and they hold the whip hand because without that Netanyahu's government falls. And having so many elections take place, therefore the stability coming from this is itself the one which will destabilize Israel. And we are likely to see therefore the growth of this conflict even beyond what it is today. That means an open espousal of export the Palestinians to other countries. Now who is going to take them is a different issue but slowly disenfranchise them, take away their citizenship, take away various rights. All of these I think are on the cards now. These things have been happening all this while. While they have been saying these are not true etc. etc. These things have been happening but this is now going to happen officially. And I think that is the nature of the state then that is going to come into question. And it's reported that when we might actually get the internal security ministry and control the police, so all the more likelihood. That's a very important point because that's how actually they infiltrated the army and now they infiltrate the police that we can see the consequences of this. Absolutely. In this context of course, big question for the Palestinians because they have I think also over the years there has been an increase in Palestinian resistance as well in various methods in various forms. And Israel has responded by in the most brutal way in 2022 I think having seen the largest number of deaths since 2005 or 2006 even when a so-called liberal government was in power. So do you also foresee the resistance sort of intensifying not only in the occupied territories but also what is called 1948 Israel over the years? I think both places the resistance is going to be stronger partly because the 48 Palestinians 48 Israelis whichever whatever term you want to use are the ones who were not openly under attack for a long time but increasingly last 10-15 years the fact that they're isolated they don't have access to various facilities they're essentially second-class citizens all of that is intensified and they have started to participate in some of the movements that are taking place across Palestine as well as what would be called Israel in that sense. So occupied Palestine or in Israel there has been movements and there has been solidarity which has been building. Which way does it go? This is a big question it will depend actually on what happens in Israel also it's not going to be Palestinians deciding alone because it's also going to some decisions are also going to be made for them by what Israel is going to do and particularly this right-wing government. So I think it's very much open to which way it is going to go and it's the part of a much larger picture in West Asia. There is also Iran there is also Syria there is also Lebanon so how all of these are going to shape up is also going to address for Israel the question are they a part of West Asia or are they just simply a western extension into West Asia. I think that's the existential larger existential question for Israel. Still with all that we are seeing now feel that they are an external intrusion into West Asia on behalf of the West. I've been moving on to the other topic which is also very significant which is that a peace deal has finally been signed in Ethiopia. This happened on the 2nd of November ending close to two years of war between the Ethiopian government and the Tigray people's liberation in front of a very brutal war huge humanitarian crisis going on there. A lot of allegations of western involvement in and their support for the TPLF as well. But finally a peace agreement signed in South Africa apparently the TPLF is said to be disarmed reintegrated into the Ethiopian political system. So could you tell us take us through why this agreement is significant and you know of course what what will happen is a big question we're not going there. But right now why is this agreement quite significant? It's been a brutal war for last two years but if you look at the larger history Tigray Liberation Front or what it represents ran Ethiopia for quite some time and it was backed by the West. If you remember also the relationship between Ethiopia, Eritrea and Somalis has this triangular relationship also has had its problems in which the United States has once supported Somalia, once supported Ethiopia and Tigray was their favored support base in the region. They destroyed Somalia after that part of history but Eritrea held out. Now this time it is the Eritreans as well as the other groups in Ethiopia who did not accept the dominance of the Ethiopian government for more than 30 years by the Tigray Liberate or Tigray based identity which ruled in this country. That led to this kind of upsurge earlier, removal of Tigray government at one point and then that was the response to the Tigray Liberation Front had. They wanted them to take back power and therefore the military revolt that took place. So the complex picture over here is not very different from what's happening in other parts of Africa but the ex-colonial powers and the United States wants to keep the African groups fighting each other and through this deciding who is the winner, who is the loser tries still to maintain their neocolonial exploitation, the resources of the region. Tigray was their favored player. Now Tigray has clearly lost the military war therefore they had to come to an agreement but how much they will still retain their power how much will they continue to be backed by the United States? These are the key questions. The future of Ethiopia as all of this colonial wars is whether the countries which are under this kind of attack can rise above the imperial invasions that are taking place by going with one side or the other whether they can really overcome that and that is a much more difficult question because already the identities, ethnicities, etc. have been fanned up to the extent that the original nation states which existed to put them back together is not going to be that easy and I think that is the much larger battle we are seeing in Africa whether it's of Saharan Africa or now in Northern Africa and already we have seen the destruction of Somalia. What's going to happen to Mali is not clear. Ethiopia has been under this kind of civil war for quite some time. So the gradual destruction of the states doesn't bode well for Africa or for the world. Can we overcome therefore the colonial interventions in this places and see whether nationalist forces are able to build a unity among themselves and therefore reject the foreign interventions that are taking place in France and other colonial power in Francophone Africa and of course the United States with its number of floating bases in Africa which we have talked about earlier. Thank you so much for being here. So there we have it an election and a peace agreement to two different regions of course but also two processes that could have a huge impact on the configurations of various geopolitical configurations around the world. We will be discussing many similar issues in future episodes of Mapping Frontlines until then keep watching your slick.


Hello and welcome back to this lecture 14 on Microsystems Fabrication by Advanced Manufacturing Processes. A quick recap of what we had done in the last lecture. So basically we were trying to study the various effects of ECM processes by looking at the kinematics and the dynamics of the process. So what we really modeled or did is that we assumed that there is a workpiece as indicated here and then there is a tool surface indicated below and this workpiece is moved slowly towards the tool in minus y direction. This being the y axis is a minus y direction so the workpiece is moved like this and then we assumed that there is a movement rate or a feed of this particular workpiece towards the tool assumed to be F. What we also tried to investigate is that while the ECM process would continue from this surface there would be a slow dissolution of the surface indicated and this would result in a change in the total thickness of the workpiece. So that would result or amount to the fact that there is a feed which is happening in the negative y direction as is indicated by this arrow here and then there is an upward movement of the surface because of the dissolution or a change in thickness of the workpiece which is happening in the exactly opposite direction. And so we found out that we can actually represent this whole kinematics by looking at the rate of change of y, y is the distance between the workpiece and the tool surface and also y is a function of t as you know because there is a continuous dissolution and feed of the workpiece towards the tool. So the dy by dt or the rate of change of this gap y between the workpiece and the tool was estimated as A times of J by rho Z F minus feed F here where Z is the valency of the metal which you are dissolving, A is the atomic weight, J is the current density vector which is nothing but the current parent area, rho is the density and F of course is 96,500 coulomb. So therefore that is what the dy by dt would amount to or look like and then you know if you just substitute the formulation for the current density which is also represented as the conductivity of the solution minus the available voltage which is V minus delta V, delta V is the over voltage potential which is has to be given the design voltage so that the amount of machining that you are intending should take place divided by y t where y is the gap. So this expression really amounts to dy by dt equals A times of the value for J divided by rho Z F y minus F and then we assumed this whole term here to be some constant lambda which is dependent on the setups and the processes and we can write this whole expression as lambda by y minus F. So eventually that is what dy by dt or the rate of change of the gap between workpiece and tool would amount to. So this is the component coming from the dissolution of the surface, this is the component coming from the feed of the tool or workpiece towards the tool. So now let us consider different cases in which various values of feed can be assumed and we try to eventually discuss or find out what is the net equation between y and these different parameters lambda F so on so forth for doing the surface analysis. So the case 1 is a case where we assume the feed to be 0. So therefore the workpiece is a static with respect to the tool at time t equal to 0 and of course as time progresses so at higher values of time t the dissolution would lead to the movement of the front of the workpiece away from the tool. So if you substitute this intended value in the equation dy by dt equals lambda minus F. So F is 0 here or y becomes equal to y dy times of lambda dt assuming that the gap was y 0 to begin with and it goes to some value y and corresponding to time instances 0 to some value t. So the y square becomes equal to y 0 square plus twice lambda t. So that is how this particular equation would be and if you plot the value of y with respect to t it would typically look like something like this here. This value is y 0 and corresponds to the value of the gap between the tool and the workpiece at time t equal to 0 and this is the extrapolated front which assumes that what would happen when y actually becomes negative at y becomes 0 at negative point of time. So typically this is like a parabolic equation equation for a parabola as indicated by this y square equal to y 0 square plus 2 lambda t here and that is how the distance would behave with respect to time when the feed F is considered to be 0. Let us analyze another particular case in this particular process of constant feed. So in this case an ever increasing gap being not desirable as was seen in the case 1 in an ECM process. So the electrode is provided with a constant feed velocity of suitable magnitude. So obviously F equal to a constant. So what eventually would happen is that there would be an illustration or there would be a case where the feed actually becomes equal to the rate of dissolution of the workpiece front. In other words there is a equilibrating condition which would arise. So this is the workpiece and this is the tool surface and this is the y value with respect to let us say the x y z coordinate system and the illustration is that this workpiece starts moving towards the tool at a constant feed. So in the equilibrating condition the amount of dissolution leading the workpiece surface away from this tool surface is exactly equal to the amount of feed of the workpiece surface. In other words in that case the gap y is maintained as a constant equilibrium gap y eq. Why equilibrium because it is essentially the two processes of the surface moving away from the tool because of dissolution and the speed at which the whole workpiece is propagating towards the tool they are kind of an equilibrium with each other they are constant. So dy by dt becomes equal to 0 in that particular illustration and that can be represented as lambda by y e where this y e or y eq is the equilibrium gap as already proposed before minus F. In other words the equilibrium gap in such instance can be calculated by using lambda by F which again means because you know that there is a certain specific value of lambda that we are talking about.  So that is how the equilibrium gap would look like between the tool and the workpiece surface and because of that reason the condition of equilibrium would really come into picture. So now let us just slightly change the paradigm and because you know ECM itself as a process is to be applied to microsystems eventually the whole kinematics or dynamics of the process should be scale independent or should be made at least a scale independent and for doing that we need to somehow non dimensionalize the equation in a manner so that irrespective of whatever be the scale the scale is known by its length scale or time scale or velocity scale and then everything is a raciometric in comparison to these scales established at any particular level of operation. So if it is a meso scale or if it is a micro scale if it is a macro scale accordingly what is varying is the scaled quantities like the velocity scale may vary the length scale may vary the time scale may vary so on so forth and then the equation can rhyme at every scale. So it becomes completely independent of the scale. So let us prepare a way or a method where we can non dimensionalize this equation ok and then we will see later on that how important this is in terms of things like roughnesses etcetera which can be predicted experimentally and otherwise using this non dimensionalization approach. So let us now use two non dimensional numbers y dash and t dash ok such that the value of y dash is represented as the actual y divided by the equilibrium gap. In other words this estimates so this gives an idea of how many times the equilibrium gap is actually the gap between the tool and the work piece at a certain point of time at a certain instance of time and also let us assume so because y is already defined earlier in this particular case as lambda by f we can just substitute the value of y into this equation and write this down as f y by lambda ok. So let us call it 1 and for the time scale so this is actually the we can say that y is the gap scale or equilibrium gap scale or the length scale at any particular range of operation it is the scale which varies and the ratios kind of remain same and the final equation which will result will be in terms of ratios to that to those scales. So the other thing is the times time ratio t dash which is represented by the actual time by the time that is needed to cover up this equilibrium gap assuming that the tool is moving at a feed rate of f with respect to the work piece. So the amount of time that the equilibrium gap would need to be covered up if f is the feed with which the work piece is moving towards the tool the amount of time is y e by f ok. So you basically ratio practically comparing the time which is available to this parameter y e by f in a manner that again this can be substituted for the value of y e and made lambda by f square. So this comes out to be f square t by lambda so let us call it equation 2. So you have now a time ratio and you have now a length ratio as y dash or t dash and y dash respectively and they have been somehow expressed as the scaled quantities by f y by lambda and f square t by lambda in both the cases. So let us now see what dy dash by dt dash would really look like. So dy dash by dt dash where these are all the ratios and we are trying to now build up an equation only based on the ratios would actually be equal to dy dash by dt times of dt by dt dash. In other words you can write this down as dy dash by dt divided by dt dash dt ok. So just using the chain rule. So here the dy dash by dt comes out to be equal to f by lambda dy by dt from 1 ok from this particular equation and the other dt dash by dt comes out to be equal to f square by lambda times of 1 dt by dt from 2 ok. So therefore we can represent this in fact as f 1 by f dy by dt and dy by dt as you all know is basically represented by lambda by y minus f from the previous equation right where we talk about the how the equilibrium gap changes with respect to time assuming a certain lambda by lambda by y sorry not f this is y lambda by y minus f and so that is what the dy dash by dt dash would be in this particular case and we can further modify it by taking this f inside the bracket and making it lambda by f divided by y minus 1 and as you know that lambda by f is actually 1 by y dash or y by y dash from this equation here ok and equation 1 and so therefore this becomes 1 by y dash minus 1 and other words dy dash by dt dash is equal to 1 by y dash minus 1 and this is the scaled version of the equation mind you these are all ratio metric quantities with respect to the length scale or the time scale dy dash is that with respect to the length scale dt dash with respect to the time scale so on so forth and now what you very easily can observe is that this equation has gone independent of the feed because the feed is somehow buried inside the information for the time ratio t dash which is equal to equilibrium gap per unit feed y by f. So, that is how you kind of have relationship between all ratios a non dimensional relationship and what I would be now interested to do is to somehow manipulate this in a manner by integrating with respect to time to see how y dash and t dash would vary as an equation. So, let us look at that part so you have dy dash by dt dash becomes equal to 1 by y dash minus 1 meaning thereby that y dash by 1 minus y dash dy dash becomes equal to dt dash and this can further be integrated with respect or between some quantities or limits and we can just simply look at both sides and try to solve what these values would be like. In fact, the left side could be solved by considering a little bit you know partial fractions. So, this whole thing can be represented as 1 plus y dash minus 1 divided by 1 minus y dash times of dy dash and that is equal to integral of dt dash and further you can just split this up into two integrals. So, you have one integral 1 by 1 minus y dash dy dash plus or maybe it is a minus because the signs are different in both minus integral of just simply dy dash on one side and integral of dt dash on the other side and in fact, if we solve this little further we get that t dash as an indefinite integral t dash is actually equal to minus of y dash minus ln 1 minus y dash plus some value k. So, let us look at the boundaries and the limits to obtain this value of k. So, we know that with the initial conditions that we started with were that this y dash would be some y dash is 0 at time t equal to 0 meaning thereby as you already know y dash is nothing, but from the previous formulation it is basically y upon y e or f by lambda upon y and you can assume that at time t equal to 0 this y was actually equal to some value y 0. So, y dash is 0 can then be defined as just y 0 by y e and that is what y 0 is y dash 0 is at time instance t equal to 0. So, if you put this value here and of course, as you know the other formulation t dash was calculated by looking at the actual time with respect to y e by f or in other words it was calculated as f square t by some value lambda. So, we can assume that at time t equal to 0 when y was y 0 and y dash 0 becomes equal to y dash the time t equal to 0 would also correspond to t dash equal to 0. So, typically when we are saying at time instance 0 t dash is 0 and y dash is y 0 dash this is y 0 by y e at some particular beginning time of the process this becomes just a ratio of y 0 with respect to the equilibrium gap. So, we put these values here.  So, that is what the value of k is and if we substitute this value of k back into the equation in question then the formulation that would finally, have would be of the type t dash equal to minus y dash minus l n 1 minus y dash plus k value which is y 0 dash plus l n 1 minus y 0 dash. In other words t dash can be expressed as y 0 dash minus y dash plus l n 1 minus y 0 dash by 1 minus y dash. So, that is how the time ratio can be expressed in terms of the length ratio where this ratio is with respect to either the equilibrium gap y e and the time ratio is with respect to the amount of time which is needed by a tool going through a feed F with respect to the workpiece to cover that equilibrium gap y e. So, that is how you basically try to plot the various relationships together and obtain a relationship on a ratio scale and this ratio is valid over all the different scales be it meso, be it micro, be it nano, be it macro. Any scale this ratio would be valid because it depends really on that length scale or the time scale for that range of dimensions that are in question. So, now let us try to make something useful out of this plot and try to plot the parameters t dash and y dash and c the various interpretations of what is important out of this equation. So, if we really plot the t dash and the y dash together in a sort of x y plot like this you can find out that for various values of initial gap time t equal to 0 you know there is a plot which is for time t equal to 0 y 0 is 4. There is a plot at time t equal to 0 y 0 is 3 or 2 1.5. So, these are different initial gaps for the process. So, you are plotting y dash on the y axis here and t dash time scale on the x axis here and you see eventually that after a certain t dash is achieved after a certain t dash value is achieved all these y dashes come very close to 1 which means that as you know by definition y dash is nothing, but y by y e. So, this coming close to 1 means that all gaps whether it is higher gap 4 3 2 1.5 so on so forth is basically tending to the equilibrium gap corresponding to y dash equal to 1 with time. So, if you look at this paradigm you can always see clearly that ECM or electrochemical machining is a sort of equilibrating process and the perturbations on a surface or the roughness of the surface really are leveled to a point when the value of y becomes equal to be whatever gap to start with it becomes equal to at a certain time scale or time ratio it becomes equal to the equilibrium gap. So, it is a case where the feed and the resolution rates are same to each other. So, whatever be the condition in terms of gaps starting gaps between the electrode and the tool eventually at a certain constant feed rate it would arrive on to the equilibrium gap. This is a very important conclusion out of all this dynamics and kinematics of the whole ECM process that we have done so far. So, basically the as we have seen that it is a self leveling process the ECM is a self leveling process and let us look at all these from a perspective of defects in terms of valleys and hills on a surface of a certain roughness and then let us see if we can do something in terms of plotting that roughness function with respect to all these different y dash t dash so on so forth. So, that is should be typically our endeavor at this time. So, let us assume that the deviations from a desired surface as written here are the defects characterized by non dimensional depth or height delta dash. Now, let us look at it in a little more details as illustrated in this previous slide here that we are working with uneven work surface subjecting it to ECM. The work surface is shown here so there are certain valleys in the work surface there are certain hills and these hills and valleys are all separated by delta dash whether in the positive or the negative direction. So, these are the sort of defects average defects which are there on the surface which eventually the ECM process should level to a certain mean value. So, the portions are projecting outwards the hills is nearer to the tool surface this being the tool. So, these hills are nearer and simultaneously the amount of electric field which would happen between the hills and the tool would be more the lines of forces would be more because electric field is potential difference divided by d d is lesser here and the valleys are at some distance from the tool which are higher diameter and therefore, if you assume the same potential difference v over another distance d 1 where d 1 is much much greater than d 2. So, the amount of electric field available here is much more sparse and as you know that electric field and current density are sort of directly proportional to each other and current density is the cause of movement of ions or machining. Therefore, current density is very high where the field is higher and very low where the field is lower. So, this guy gets dissolved away at a faster pace and this at a slower pace eventually equilibrating on the same surface. This is same as saying that ECM is a dye sinking process as we have mentioned before many times while introducing this topic of ECM. So, therefore, if you look at the portions projecting outwards they get machined more quickly on the projecting inward portions like cavities they would not get machined that quickly and therefore, there is a smoothing out of the unevenness. So, if delta dash be considered as the desired deviation in terms of defect from a mean value of the surface we can have an equation of delta dash in terms of t dash. T dash as you know earlier is the ratio parameter between the gap at a certain point y per unit the way that equilibrium gap or the time taken by the equilibrium gap to be moved. So, t divided by y e by f is what the t dash was before. So, depending on whether the defect is a valley or a hill. So, this is the since delta dash equals y minus the equilibrium gap let us say eventually the gap which would come is y e and delta dash is really how much above the equilibrium gap this y e is if you assume that the surfaces become even at equilibrium from this position it goes to this position at equilibrium. So, y minus y e is delta and so this is delta not delta dash. So, delta dash I am sorry and delta dash is the comparison of this delta per unit the scale which is available of the length scale which is available which is really the equilibrium gap. So, delta by y e. So, this becomes equal to y by y e minus 1 and y by y e as you already know is y dash. So, it is y dash minus 1. So, delta dash emanating from this delta the difference between the equilibrium gap eventually y e of a hill or a valley let us say this is the smoothing line which corresponds to this line here. So, this is y e. So, if it is above y e or below a v it could be a plus delta dash or minus delta dash as we have seen before as has been illustrated before. So, similarly so therefore, you know in the same manner as you have illustrated this particular gap for a certain delta is essentially a case where y equal to delta right. So, the same equation should hold valid. So, therefore, t dash can be written down as some delta 0 dash at time t equal to 0 assuming delta being equal to delta 0. So, delta 0 dash minus delta dash plus natural logarithm of delta 0 dash divided by delta dash and therefore, the whole idea is that the t dash that we are looking into is actually equal to this delta 0 dash minus delta dash plus l n delta 0 dash by delta dash. Theoretically if we look at when this delta would go to 0. So, it would take an infinite time to remove the defect completely because delta going to 0 means delta dash going to 0 and delta dash going to 0 means that this t dash which is exactly equal to t divided by y by f if you may have recalled the way that time scale was defined would also depend on this l n of 1 something by 0 l n of infinity. So, it is undefined. So, theoretically it should take almost an infinite time for the delta dash to completely go to 0 which may not be possible, but practically you have to just wait for and sort of value where this delta dash is so small that it is insignificant in comparison to may be the equilibrium gap y e. So, we really need to wait for just a sort of time instance t up to which this delta dash may not be equal to 0, but very very close or negligibly small and can be considered for all practical purposes to be 0. So, that is how you can get an idea of when a surface of a certain average roughness again given by delta smoothens out due to the smootening effect of an ECM process. So, if you start with the certain roughness start with certain surface roughness and your design specification says that you have to have a roughness which is within a tolerable limit which has been given let us say or proposed by the design. You now have a basis of how much time you need to wait for an ECM process. So, that a certain roughness to start with on the workpiece surface has been eventually smoothened to a desirable tolerance or desirable roughness or a desirable tolerance value which has been specified by the engineering department of a certain component. So, this is an advantage of doing this scaling theory or scaling equation that you get a time estimate of what would be the product surface roughness if you start with a certain particular in this case for example, delta is the roughness which you are starting with and you are aiming for delta to be so negligibly small where you can consider it to be insignificant and therefore, t dash the time that is needed really times time ratio that is needed for going from delta to that small value of delta which is negligible that is easily estimated by an equation like this. So, we can plot the various things together in one dimensional plot as has been illustrated here and as one can very clearly see there are let us say the hill sides and valley sides of the process where delta and the valleys can be minus delta sorry plus delta and delta and the hill side can be minus delta. And you can see that if the initial defect size is given on the excess scale here meaning thereby that this corresponds to some delta 0 and delta 0 dash of course, is what it is delta 0 per unit equilibrium gap is that is the time the roughness ratio. So, you are starting with this particular delta 0 value as you can see here and the delta 0 can be either a minus delta 0 if it is a hill or if it can be a plus delta 0 if it is a valley and then on the y scale we are plotting here the depth of ECM in equilibrium gap units required to achieve the certain tolerance which is indicated. So, these are so these really are the so called depth of ECM in equilibrium gap units terms. So, the ratio of the depth that is needed in let us say the so the y by y e value which is needed in terms of equilibrium gap units and the tolerances that eventually come up or eventually are needed are indicated on these curves here. So, for example, if you want to achieve a tolerance of 0.01 that means about one hundredth of the equilibrium gap that is how I would like to mention this tolerance as. So, you have to start with a certain initial defect size let us say delta 0 dash and then you have to move so much in terms of units of equilibrium gap for this tolerance to come up or for example, if you want almost 2 percent tolerance on the equilibrium gap. So, you will have to move so many units in the as mentioned in the y scale here in terms of equilibrium gap units. So, this much distance you have to move for eventually getting a 0.02 tolerance or if it is a 5 percent tolerance or a 10 percent tolerance you have to move correspondingly. So, many you know distances in terms of the equilibrium gap units that means the y value essentially for hitting this tolerance. So, therefore, it is a very clear cut specification sheet which has been generated which mentions about from what defect size or initial size of the defect how much y has to be moved by a particular work piece towards the tool. So, that you can achieve a certain percentage of the equilibrium gap as the tolerance size. So, that is how the whole plot has been made generated and this plot can be used as a sort of thumb rule for you know a process engineer who is working in a ECM process. So, the plot is different if you go towards the plus delta side that is the valley side and it is different for the minus delta side the hill side for obvious reasons that this gets depreciated much more faster than sorry this gets depreciated much more faster the hills get depreciated much more faster than the valleys because the gap of the hills are lower with respect to the tool and the electric field intensity and the current density is much higher as has been explained before. So, let us actually now look at some numerical design problems let us say in an ECM operation with a flat surface as you can see here a 10 volt DC supply is used and the conductivity of the electrolyte is given here as 0.2 ohm inverse centimeter inverse a feed rate of 1 ohm per minute is used and workpiece is a pure iron meaning thereby that there is a the machining the surface to be machined is that of iron. So, all the parameters related to the electro chemistry of iron needs to be known here and you are wanting to calculate the equilibrium gap and you consider that the total delta v the over voltage which has to be also taken into the design voltages 1.5 volts. So, let us find out first of all what are the different parameters for the workpiece material that is iron those. So, for iron Fe the atomic weight of iron as you know is 58, 55.8, 55.6 grams iron normally dissolves in divalent state ferrous state Fe plus 2. So, that is equal to plus 2 at least the lowest valence state is treated here and then the density of iron is 7.86 grams per centimeter cube and as we know that the equilibrium gap y is given by lambda by F and lambda is conductivity times of the atomic weight of the particular species v minus delta v where v is the applied voltage delta v is the over voltage divided by rho z F coulomb or 96500 coulomb or Faraday's constant times of the feed rate F and we already know that the feed rate is given to be 1 mm per minute meaning thereby it is 0.1 centimeter per 60 seconds. So, this is in centimeter per second 0.1 centimeter per 60 seconds and we first find what y e is. So, the conductivity is 0.2 ohm inverse centimeter inverse atomic weight 55.6 times of v minus delta v as you know 10 volts is available voltage the over voltage is 1.5. So, you have 10 minus 1.5 as the v minus delta v term divided by 7.86 gram per centimeter cube which is the density times valency which is plus 2 times of the feed rate which is 0.1 by 60 times of this 96500 coulombs which is the Faraday constant corresponding to this feed rate. And therefore, this can be calculated to be as 0.1 centimeter per second 0.4 centimeters which is actually about 0.4 millimeters or 400 microns and that is about how the equilibrium grab would typically look like. So, you can have an estimate of what is the level of gap that we are talking about 400 microns is actually 4 times the diameter of human hair. So, that is how small the equilibrium gap is in any electro chemical machining process and you can assume that the amount of pressures that are generated by the fluid which moves through such a small gap is huge. And therefore, sometimes of the pressure values are rhyming with the ultimate yield stress of the material then there is a possibility of the surface getting deformed the electrode surface getting deformed because of the pressures which are generated by the so called electrolyte. So, theoretically the equilibrium gap though can have any value, but there is one small constraint that is important to be mentioned that for rough surfaces if the average roughness is above 400 microns. And in that case 400 microns cannot be an equilibrium gap because it will result in shorting of the two surfaces. And so, that practical constraint has to be taken into picture that what is the average surface roughness and the equilibrium gap also has to be always at least more than twice the surface roughness. So, that is how we have a thumb rule of how you can position this the tool with respect to the workpiece ab initio when you start the process. So, that is about how a ECM process would function. Let us actually do another numerical example here of surface roughness with respect to the gap. So, you know that this is a highly irregular surface as you are seeing here of the tool as well as the workpiece. And the surface irregularities of the electrodes are 5 microns and 8 microns with respect to flat surfaces respectively thereby meaning that these are the irregularities with respect to the mean value of the surface. And in one case it is 8 microns in the case of workpiece in case of tool it is 5 microns. So, the total amount of equilibrium gap at least needs to be 8 plus 5 that is 13 microns for the process to be without short circuiting and still go on. So, if supposing the work is again of pure iron we assume iron for the sake of convenience here as well iron is in fact the most machinable material with ECM process also. And a DC voltage is employed of 12 volts. So, you estimate the largest possible feed rate that can be used and you assume the conductivity and over voltage to be the same as before. So, here for example, the minimum allowable value of the nominal gap so that the electrodes do not touch each other is about 13 microns. So, typically the y e value in terms of centimeters is 0.0013 centimeters. The corresponding feed rate F is again given by the equation K a v minus delta v divided by rho z faraday constant times of the equilibrium gap. And we know pretty much everything we know that what is the conductivity we can assume it to be the same as the previous question 0.2 ohm inverse centimeter inverse. This is known as 56 grams this is about 12 volts over voltage employed can be treated to be the same that is 1.5 volts. And then of course, you have the density of iron as 7.86 grams this can be plus 2 this can be 96500 and y e here is defined by this process as 0.0013 centimeter. So, the maximum allowable feed in this case also gets defined as 35.7 millimeters per minute which suggests that the feed rate cannot really go on increasing it is really limited to the amount of average roughness which is available on the surface here. So, that it does not have to go so close to a surface that there is a shorting or you know the ECM process modifies because of that shorting effect. So, I think we are towards the end of today's lecture, but now as we go on we will see some of the other parameters of design which are needed for an ECM process. For example, electrolyte circulation or electrolyte boiling and this phenomena would be very important because in a MEMS scale when we apply such processes because the feature sizes are too small they are more amenable to thermal energy you know the getting heated up and getting evaporated or getting faster dissolved and therefore, one has to be very careful to design even the electrolyte as a small simple thing as simple as even the electrolyte velocity in that process. So, with this I would like to end today's lecture. Thank you.


JP, it's time for JP's product pick of the week. We've all arrived just in time. Thank you so much for stopping by I'm gonna pause the little video re echo in the side there. That's gonna drive me mad mad. I say So what the heck is this all about? Okay, we'll talk about it Sometimes I use the AI inside of Photoshop to make backgrounds and thumbnails and boy is that one weird So, hey What's happening here? We've got people over in our chats. So thanks for stopping by. Thanks anyone Over on our YouTube chat as well as our discord chat if you're wondering where the chat is That's the place to check it out. That is at a to fruit dot it slash Discord and then you can look for the live broadcast chat channel right There that one you see that You can see my cursor you can't right there But that's it. That's the live broadcast chat channel. That's where people hang out during the live stream So go check that out if you're wondering where people are hanging out What else you can see I've got a Suspicious backdrop here because I'm prepping for the eight a box unboxing tomorrow night So come by it'll be at five o'clock Pacific time eight o'clock East Coast time same time as the normally Ask an engineer Wednesday show, but this is an ass a an eight a box unboxing takeover. We're gonna do So come by for that But I'm prepping for that so I've got a little backdrop situation happening What else so I've got a cool product pick for you today and You can go if you want to get a jump start head on over to that URL right there It's the product ID 5724 you can also Use your camera device to point at that QR code if you like that sort of thing That'll take you to the product pick and this show is being broadcast from inside broadcast right in there in the product page You can get it at a humongous discount, and you don't need a coupon code or anything like that You just have to buy it during the show. It's gonna be half off And we I think stashed a good good number of them before the show so go check that out I will tell you all about it in a moment and show you a little demo But before I do I will have lady Aida introduce this by jumping back slightly into the past take it away lady Aida The can feather So really I'm cranking out these RP 2040 boards with different peripherals on the right hand side I always wanted a board that had canvas built-in for easy plug-and-play No solder can projects and the RP 2040 feather is a great place to start that so It's got your classic RP 2040 chipset. That's a dual core Cortex M zero on processor nice chip We pair that with eight megabytes of Q-Spy flash. You'll use that for your program or your files That's kind of the middle top area there. You've got boot and reset button so you can do the bootloader and Reset button of course you can reset whenever you want. It's got USB type-c for data and uploading firmware and debugging LiPo battery built-in with battery charging through USB-C so you can take this project on the go There's a stomach UT port as well And then in the you know, the feather pinout is standard It's got you know, 21 GPIO pins and four more analog and two iSquared C ports and two SPI's and two UR so it's got a lot of stuff going on with it Great for use with Arduino micro Python or circuit Python and then what I did is on the right hand side I stuck a MCP 25 625, you know, like I've never heard of it. Yeah It's basically a chip that has inside of it an MCP 25 1.5 Which is a very very popular can controller plus a can transceiver It's just they just took those two chips and they squished it and they called it the 25 625 But the firmware you run on it is MCP 25 1 5 like firmware wise what the code you'd run for this chip controller is like the most popular can controller We've got Arduino code for it. There's circuit Python I think micro Python also has code for it pretty much any programming language is going to have code for that can controller Because it's the most popular one in the world There's also a little switch-capped boost converter Above it that'll generate the five volts so you can do can bus with five volt power because you use a five-volt power Sorry five volt logic Interface so the feather still running at 3.3 volts, but it has the five volt necessary to do that the can controlling There is a terminator a 120 ohm terminator Which you can disable by cutting that trace you need at least one termination on your can bus and then three terminal blocks low Ground and high so now you can plug into any can bus. There's a differential signal system your shared ground which is handy and then low and high and then you know Terminal screw on how many wires you want to shove in there and they're pre soldered So it's a new thing. I'm trying to get more boards where you don't have to do any soldering It's plug-and-play if you'd like to use it on a breadboard you can solder Headers that comes with this photo shows it. Yeah, we've tossed some headers in but you know If you don't want to use the headers you just want to do can you're ready to go and again We've got Arduino and circuit Python code and we also have you try F Which is a software that runs a firmware that runs on the RP 2040 and allows you to use your computer To connect a can device so it's like it acts as a USB to can bridge Which is very handy and then of course if you want to add sensors so you want to get can node with sensors There's thank you teaport you can plug in almost any of the many hundreds of Stem and qt or quick or picodev boards that come with the connector Yes, that's right. You can do all of that. Let me show you a little shot of it here I had to hide some of it because I've got it all connected up to some stuff I want to focus there for a second that is it right there And I will introduce it properly for you this Right here this that's my product pick of the week this week. It is the can bus rp 2040 feather This is a feather rp 2040 with all of the usual feather rp 2040 stuff that we love and on the end of it It has the can bus controller and transceiver built in so this is based on the very popular 2515 Controller, but it also has the transceiver built into it. So it's all on one package does everything you need The chip name and now I'm forgetting it because it's actually with those two things bolted together What's your name? It is the Yeah, so it's the mcp 25 625 which integrates the controller and the transceiver onto there You can see I have mine hooked up using these fuel office paper very convenient Screw terminals that we have there to my twisted pair for the high low differential signal as well as ground And what you do is connect that to other Can devices on your can network. So A little bit. I'll talk a little bit about can let's take a look at the product page and the the learn guide And then I'll show you a little bit of a demo in a second. So First of all, what is can can we associate it with cars? It's actually controller area network But it is it is a car an automate automotive thing initially And Oh, I'm getting a I'm getting a note that my audio is low. What the heck's going on microphones Let me know if that's a little better. I don't want to blast it out Uh, oh, I know what happened Okay, I'm not gonna mess with that thing there. Is that gonna Well, we'll see here. Let's let's goose this up. How about that? Yeah, that's getting close to zero db so the can is a Was originally designed as a way to cut down on the immense amounts of wiring inside a modern automobile I think this was in the 80s that this uh, bosh came up with this this Uh Technology so the idea is rather than having point-to-point sensors all heading to the front of the car Where you have a central Processing unit dealing with all kinds of different, you know, antelite braking sensors tilt sensors seatbelt sensors all of these things Build a network so that you can have a single wire that's running Among many many many of these sensors passing the data along You can use star topology. You can use daisy chain topology and it just cuts down on the immense amounts of wiring the way that the Feather rp 2040 can bus controller works is that we have the feather using actually on board spi connections to talk to the mcp transceiver and controller chip and then that is Taking all of the the messages in and sending out messages can go both directions to any other devices any other can devices on the network I was uh Previously I was thinking that one of the main uses for this would be car hacking and someone asked. I think it david david glau de david glau de in our chat asked about Using this for reading like from your odb 2 port Certainly that I believe is possible with this. It is able to speak can The Thing is it's actually useful for a whole slew of non-car and non-car hacking things because it is essentially A way to network devices that is Much more electrically robust than spi or i2c has much longer wire runs than those you can do I believe it is 120 feet in a One megabit per second and you can get Like a thousand meters long if you're dropping it down to like 50 kilobits per second So depending on your needs you can really send your data a long long distance with great Integrity it fights noise by being a twisted pair differential. So the messages have a high and a low. That's what those two Terminal positions are other than the ground is that when it wants to send a zero It goes high on the high and low on the low and then comes back down So there's some some noise essentially cancellation going on there. You're not As worried about little voltage spikes. It also counsels out electrical interference. It doesn't send out Interference because those are equal and opposite waves or differential voltage signals on them. So really really robust You can Connect up multiple of these And have one that's kind of your main unit, but they can all talk and listen Yeah, deba dogs has used an aircraft using a lot of robotics applications But anytime you're thinking hey, I kind of need a long run of a couple of or many more than a couple of microcontrollers And sensors talking to each other. This is certainly worth considering The let's go to the product page here for a second You can see here. It is 50 off today. So nine dollars 98 cents That's I think the price of a regular feather, but you're going to get it with the regular feather rp24, but you're going to get it with the controller and Terminal block on there to do all of the can bus stuff. So why not? It won't interfere in any of the regular feather stuff But if you're thinking of picking up some feathers, maybe get one with a with a can bus or get a couple of them So you can talk You can see here if we scroll down we've got Some links with info about this. We have a link down here to the learn guide so if you click on over Here, this is the main learn guide. Liz Clark put this together. Thank you, Liz. We have Pinouts for power management. You can talk to it in circuit python. You can use micro python You can use arduino. We have setup instructions and examples for using psych with circuit python and with arduino Here's a an example here the can bus test You can also test stuff in a loopback mode So it'll send and receive its own messages if you don't have multiple devices It's also a lot more convenient for for setup versus two Circuit python devices plugged in at the same time and you're trying to write to them You can do it, but it's it's actually kind of nice to be able to Program just the one on its own The Let's see. Yeah arduino same sort of thing. We've got a can bus test that you can run in there You can also go down to the downloads page and here is the Um data sheet for the controller from microchips mcp 25 6 2 5 which has that 25 1 5 Controller in it as well as the trance ever and this will give you some of the info about operating temperatures speeds I think the wire Run distances may be also in here as well, but that's an easy one to google So this will tell you In great details an enormous data sheet in great detail everything you need to know 90 pages long So if you need to know it, it's probably in there But what I thought to do is give you a A little example of a couple of these talking to each other. So what I've set up I'll go to my Down view let's see. Yeah, let's go to this Let's go to this configuration actually Not that that okay So you'll see here. This is the one I was showing before This is a How I have that set up so I can get it enough out of the way um, so this is the Settle light here. This is the feather. I've got uh three wires coming off of it I happened to just cut the ends off of a cat 5 cable and I'm using some of the wires from that Uh, just requires three wires and I've also got over stemma qt See we've got the little quick stemma qt port there I have a rotary encoder plugged in stemma rotary encoder and then this is actually a pretty long Run of of wire here. This is I don't know 20 feet or something like that. Uh, no problem. So that's running to second feather rp 2040 can bus controller there. I'm just going to weigh down this Table so it doesn't go flying away. Uh, and on this one I have an OLED screen So this will show us data coming from Uh, the first one here. So if I step back, uh, and you watch the screen there It is receiving messages. I just have it sending the Incrementing or decrementing of this rotary encoder that's built onto there You can also see it is listing the address. So these, uh, you give them unique addresses So you can filter things you can prioritize things based on which Can device on your network is doing the talking And uh, this is you can see Got no problem whatsoever with incredibly Long runs and it is super robust. It's not dropping any messages there. That Is one of the huge benefits of the can network Let's see What else so here here's some nice close-ups you can take a look at there The benefit that la more mentioned of having it essentially be solderless is that you can plug in power to it You can plug in a battery. You can see on this one I've got a little lipo battery neither of these are actually plugged into usb right now It'll charge the lipo from there because it's a feather and You can plug in stem acute devices over that stem acute teaport to add sensors knobs displays And you can plug in your Three wires for the can bus using those terminal Connectors aren't there so no solder necessary Of course, you can solder it if you have a have a project that needs that but it's actually Essentially plug-and-play buy it Screw some things into there into those screw terminals give it some power Code it over usb and off you go This could be Many sets of wires coming into any of those ports. It's it'll just daisy chain along You can set up little wiring hubs if you want to but there's no There's nothing no router necessary of any kind. They are able to daisy chain or able to star Configuration the wiring we could have plenty of wiring spliced along the length of this going out to different controllers. So Really really neat protocol And mic ps this is yeah, you could use any three wires Twisted pair is what they specify for Best reduction of any kind of electrical interference. I happen to be using a cat five cable that I cut the ends off of But you can use Three wires is all you need to connect those up And an ethernet cable is is a really good choice because you probably have tons of it laying around Does not need to be shielded So you can get away with cheaper lighter easier to deal with easier to bend wiring because the twisted pair and the differential signal takes care of Any noise problems you might have so it's a Much easier than if you were having to deal with using a shielded cable Nothing fancy there And you can of course also get away with just using three wires of pretty much any kind as you get to longer lengths or in More electrically noisy environments such as inside of a car or a robot or an automobile Then you you probably do want to go with the the twisted pair for the data Other questions does the gauge wire have a bit of calculation for the total distance What would you say the best size wire is I do not know I would google that I am a newcomer to canvass. So I really don't have I don't have any info about the the best possible gauge for that Rufus mentions you can also actually just use two wires all paralleled. Yeah, I think the ground is a Is a nice to have but I don't think it's necessary. So I think you can just do the high low differential Um Yeah, Todd mentions you could use old phone Twisted cable pots cable as well since you only need three or four cables So a couple pairs of those plenty plenty of options lots of good diy options given the fact that you're using either cat five cat six Phone cables are really good options Uh What else any other questions? Uh, yeah, it's got those nice oval reset buttons these cute little Buttons right here that you can use as a User button once it started a boot button for initially getting into the boot loader Reset buttons a reset button. Uh, we've got some neopixels on there I used that just to help myself distinguish between the two boards one's purple one's Bluish so I could tell which one I was doing stuff on in my code And let's take a look actually at Some code right here My code window And I'll plug this one into a usbc so that we can Look in the repel there Disco tool disco tool actually Yeah, that code's fine. We don't need to resave. Um, so if I send Messages by twisting this one now from wherever I want it could go all the way across the workshop You can see those those messages coming in which list this guy's unique address and then the integer of What my rotary encoder is doing? So looking at the code here you can see the library is Adafruit mcp 25 15 So again, that's the name of the controller even though this chip is the controller plus the transceiver bolted together The library is still the 25 15 adafruit underscore mcp 25 15 Can i o importing message and remote transmission request and then From the 25 15 library importing 25 15 as can Set up here. I've got my spi bus Set up and then i'm creating the can bus with can on spi told it what the chip select is Right now loop back and silent are false You could turn those true if you wanted to just have messages sent by one looped back to itself during testing And then i'm using i2c only because of this Screen this little led screen on here. That's not necessary for using the can bus With that set up all you do in the main loop is with the can bus listener Look for messages. So the message count equals listener in waiting If we get a message then i'm taking that message and i'm just sort of unpacking The message into a readable format so that I could print that address and that number there But this there are some nice example code Nice code examples in the library you can check out you can Do the basic example of send and receive you can have just a receiver just a sender And then a few I believe more advanced examples involving interrupts It is possible to have some messages Come out on top really important for cars you want things like anti-lock breaking to Send their messages with priority over a headlight controller for example So you can do certain filtering and prioritization in can I just haven't done that. I don't really know how that how that syntax looks, but those are possibilities within can itself Let's see any other questions There's a nice Link let me bring up my discord here that liz put up to a project from calling furs furs Super famous youtuber whose name I can't remember he pronounced His project of a Some sort of vehicle contraption there is using A can bus to communicate among things. Yeah, I've seen projects online of Can bus used for non vehicle things for example Someone who had a hackaday project with some solar panel metering Used can to talk between a sensor and a raspberry pi So there's a lot of possibilities using this as as a communication method between your devices All right, have we done it? Do we have any other questions? I think That'll probably cover it. I said all I have to say. I think so So yeah, let's wrap this up That Right there's my product pick of the week this week. Are you upside down? You're right side up That's my product pick of the week this week. In fact, let's uh Let's show two of them. That makes the point, right? This is a network Product pick of the week this week. It is the feather rp2040 can bus Freighter for industries. I'm john park and this has been jp's product pick of the week. Bye


What's good boys party six and oh going into another big 10 matchup taking on the Hoosiers Honestly should be an easy game Vegas says minus four and a half Nebraska was supposed to be easy, too That clearly wasn't we're ranked top 10 and so is you of them Got a five-hour drive to Bloomington, Indiana where a memorial stadium is where the Hoosiers play we got phobee It should be a good time. I'll see boys when I get to my house. We're gonna drop off phobee Where are we? Where are we? Are we with your sisters? You might notice I don't have MSU gear on we don't want to roll to the bars in all MSU. I really don't want to get in a fight today We're looking up Venus God videos right now.   It looks exactly like I'm telling me. I'm like, bro, that's her.  I tweeted out. What's the best bar everyone said? Kilroy's right?  We're rolling up at 940 Hey, welcome to Bloomington This is actually so cool with the bug yeah, it's kind of raining out but once you get in the bar doesn't matter anyway I remember my first beer.  It was a tall beer. They have a basic fingering chart to finger Is he answering? No. Hey Apparently she doesn't respond to that in her daily life. That's so lame.  Hey Spartan fans, golly recap went to Kilroy's great bar so many people here's my first impression Number one, Indiana women are so much less attractive than MSU women. It's not even close That doesn't mean we didn't have a good time. It just means we're shallow disgusting misogynist pics.  Tarn got an aggressively hit on by three moms We stood there for like an hour and a half. They got his two beers Yeah, we're gonna get after it. Let's go get breakfast and we're checking out. Let's go Yeah, I'm not very good at directions We're trying to find breakfast right now and I shouldn't be the lead here Dude, the dunks are holding up day two of the bars You have two days at the bars one MSU game now. We're on to second MSU game dunks are staying strong got some creases But it adds it adds character That looks so good me to pop him on the annual Oh Postgame interview They were literally how do you think they were 55 the one was the one could have been their mom She could have just smoked a lot of And one was a judge the only video there is Because you can say she was a judge when we were with all the moms I just grabbed this random group of people like these two people hanging out. I was a yo about to take shots with these Moms I want this memory for life.  I want milk mommy As you're doing the motion I checked my phone. It's mimosas o'clock That's disgusting look at this Dude I can obviously peek at you Can you give grapes or birds about fun?  She was really mad. I don't think she's kidding I think she's kidding. Yeah, this would be a tough game. I'll lose, bro Welcome to Memorial Stadium, baby Hey, we're two for two getting the camera through However, low key it would be cool if you and mission we're both on the feet So and that is it playing Our starting quarterback is her Knowledge It's seven to three MSU's up. We just got to pick six. So this is this our first time walking in this look nuts I Did steep Watch right now. Why aren't you at the game? Hey, good to meet you bro. Have a good day Joe by Seekie by the way, this stadium is sick.  So Seekie.  You already know This is classic MSU football right now. It's 79 is a close game. We're horrendous on offense We have we have 51 total yards of offense 39 Give me just got some people if 51 total yards offense and 40 penalty yards It's literally embarrassing how bad we are right now. They just have been able to capitalize on touchdowns. So it's still nine to seven, but This is a scary scary game right now a great part my Bella's boyfriend We talk about that every time she's dating the punter, bro I Incredible too. That was an excellent kick Let's go let's go The Indiana security are the nicest people we've ever met in our entire lives We're just standing on the front walking dark rail and we're nobody's moving us. It's We're about to take an eight point lead which is clean They gotta get a two-point even if they score touchdown. That's beautiful We've been at like 430 and then put us at like Harper's near like 10 If I'm doing that I need a blue shoe and I need it right now blue shoe, please bro Just send me a full box. So I never run out Keep up the work Oh Yo, I bet staff was amazing these guys are incredible. I gotta get a picture of you. This is my guy right here. This is my guy I'm defeated, baby. That was a close one, but we squeaked it out got a game ball out of it, which is so sick Indiana is awesome.  So we're excited. We got you of them next got Purdue after that We got a crazy-looking schedule. We're undefeated going into you of them.  Thank you for having us. Peace