Day 4 session 1

[00:00:00]places. A very warm welcome to the first technical session of the fourth day of this 5-day online short-term training program organized by department of CACIT CC IML of BCT Darapur under the ages of the Institute of Engineers India Durapur Local Center and it is technically sponsored by the IP online. Today's training program is organized by promising area of modern electronics and device engineering titled programmable optically variable resistors and their applications. To deliver this lecture we are honored to have with us Dr. Ortra Achara, assistant professor in the department of electronics and communication engineering at Kolani government engineering college. Dr. Rajaras earned his B in electronics and telecommunication engineering from Bengal Engineering and Science University in 2007 followed by an Mtech with first rank in 2010 and PhD degree in radio physics and electronics from the University of Kolkata Kolkata in 2016 with over 16 years of teaching and research experience. His expertise spans nano electronics, millimeter web and terahertz devices, IoT, opto electronics and flexible sensing technologies.

[00:01:26]Before joining Kolani government engineering college, he served as an assistant professor at Kjihar Government Engineering College and Supreme Knowledge Foundation group of institutes. Dr. Aaria has published more than 200 research papers, books and book chapters and has contributed to several prestigious research projects including Indo-Japanese collaboration and T DST funded initiatives. He has received numerous honors including the IE journal of education award and he is professional member of IT and the institute of engineer. He is also a Japan invited speaker and session chair at international conferences.

[00:02:14]Today he will share his expertise on programmable optical electronics and VR application a topic that holds significant importance in the advancement of intelligent electronic system sensing technology and next generation computing platforms on behalf of the organizing committee I extend our heartful gratitude to Dr. Oritraasar for accepting our invitation and taking time to be with us today. Ladies and gentlemen, please join me in extending warm virtual welcome to Dr. Oritra Achara sir and the platform is now yours sir. We look forward to your presentation. Thank you sir.

[00:02:55]>> Thank you. Thank you for this gesture.

[00:02:58]Uh I welcome all of you the participants and dignitaries present here uh for my presentation.

[00:03:07]Uh first of all good morning to everybody. Let me share my screen first.

[00:03:26]Can you tell me whether my screen is uh showing or not?

[00:03:31]>> Yes sir, it is clear.

[00:03:34]>> Okay, let me start. Okay.

[00:03:36]Uh today the uh my title of the talk is the programmable optically variable registers and their applications. Uh I think it is a very quite interesting topic and uh it is not complicated.

[00:03:49]Okay. It is very simple and easy to understand. Uh if you if you have the knowledge of uh 12th class uh physics then you can understand uh that what is uh the working principle of this particular device. Now let me start with the introduction. We all know that uh in the electronic circuits or electrical circuits whatever uh there are two major components. One is the resistor, one is the capacitor and another is the inductor. Okay. Now um resistors are the most frequently used uh electronic component for both DC as well as the AC circuits. And in various applications whenever we want to uh whenever it is it is needed to change the resistance value uh we use the potentiometers.

[00:04:39]Potentiometers means on mechanical device uh which is capable of changing its output resistances by rotating some knob or rotating some mechanical arrangement. Uh by by that way we can change the resistance values. Okay. Uh its applications uh are various electronic devices like variable gain amplifiers uh sensor calibration or any kind of uh tuning circuits where resistance variation is required. But in modern day electronics everything is going to the uh automation. Okay.

[00:05:20]Automations means uh there should not be any human intervention. uh all things should be controlled by means of some microcontroller or micro computer whatever. Uh so in that case the manual mode potentiometers are not compatible because that does require the manual intervention that means the manual tuning of uh the mechanical arrangement.

[00:05:44]That's why uh one particular device is there in literature that is called the uh voltage control resistors. That means it is a device where input side is the voltage and output side is the resistance. By changing the input voltage, the output resistance can be changed. Okay, that is the concept. This is called the this is called the voltage control.

[00:06:10]That means it is a device. So there are two types of voltage giving the resistance changing the digital potential another can you remember from the practical classes of bet or whatever in the in basic electrical engineering this particular device is called the riostat by changing the position of this particular slider we can change the resistance value and it is used for the high power circuits like in the order of hundreds of watts to kilow. Okay. So this resister device is useful for the electrical circuits mostly. But for the electronic circuits we all know that we deal with very low voltage and low current applications. That's why its miniature version is the potentiometer which is used in uh various electronics laboratories. This is the this is the uh photograph of the potentiometer where uh there are three ports. There are three ports. One is the common uh it is the internal structure. There is a weer.

[00:07:23]Okay. This wiper is in the touch with uh a resistive strip and two terminals of resistive strips are connected to two other terminals out terminals of the potentiometer. And um if you consider the resistance between these two terminals then weer uh depending on the position of the whipper the resistance will increase or decrease. Whatever the amount of resistance will be there the other part will have the uh total resistance value minus the this portion resistance value. Okay. So it will provide you the potential divider circuit. So by changing the position of the wer we can change the resistance of two different ports. But uh thing is that the summation of resistance um all over resistance will be always constant and its application is low power devices as I mentioned in the order of mill to wt remember.

[00:08:25]Now why the voltage control resistors are essential for the electronic circuits? As I mentioned for the automation in electronic circuits, uh we have to use the voltage control resistors. Voltage control resistors have two types. One is the motorized real state, another is the digital potentiometer. As I mentioned in my introductory slide. Now what is motorized real estate? It is nothing but one simple riostat having one stepper motor connected to the uh slider. Uh SL it it is a stepper motor is coupled with the slider. Okay. By rotating the stepper motor by controlling the position of the slider we can change the resistance. So it is a huge mechanical arrangement. It does require some external power in order to energize the stepper motor. Okay. And its response is very slow first of all because it is it is made for the high power electronic surface not for high frequency electronic applications. Uh another uh disadvantage is that it is very bulky and heavy requires external power. So it is not compatible with the compact and low power electronic applications. So for the compact electronic applications there is a digital potentiometer where digital potentiometer is nothing but a controller guided uh resistor array where uh these two terminals are the end terminals uh this one and this one in between them there is register array.

[00:10:01]Okay.

[00:10:02]By by by by switching this MOS switches that mean the COS switch uh by switching those MOS switches we can select how many resistors will be connected at the output terminal. In that way we can vary the resistance but um problem is that since it is the resistor array assisted uh resistance variation that's why the continuous resistance various variation is not possible. These are the diskit resistance variations. Okay. So output is diskit. That's why the resolution is limited. Uh it is not analog device and its input control is the 8 bit or 16 bit uh depending on your reportment and output is discrete values resistance which can be varied from few kiloohms up to few mega. But the resistance change is not analog in nature or continuous in nature. It is in discrete nature as I mentioned.

[00:11:06]Now for very precise control, very precise tuning of many uh high precision sensors, we do require analog control of resistance by means of input voltage. So digital potentiometers although it is commercially available uh it does not compatible with those analog requirements analog tuning requirements.

[00:11:31]So we need the analog VCRs. So from this particular need our research is motivated. Okay. So what we have done it is very simple to understand. First of all within an closed enclosure suppose it is in closed enclosure we have connected one LED at one end and other end there is an LDR. LDR means the light dependent resistance. You mean I think you have the knowledge about the light dependent resistor. Light dependent resistor is made of a particular material which is light sensitive u light sensitive compound like the cadmium sulfide cadmium celeride etc or lead sulfide zinc oxide those are also very commonly used light dependent register materials but most commonly and commercially available light dependent register material is the cadmium sulfide. Now if we if we enclose one LED with an LDR within an closed enclosure and there is no ambient light interference into it within the closed enclosure there must be some gap between LED and LDR and that gap may be filled by means of some transparent or translucent material which is called a spacer and as we we have named it as the spacer. Okay.

[00:12:56]So thing is that whenever we give some input forward bias to the LED, LED will start to eliminate light. Depending on its material, it will eliminate particular wavelength range uh and that light will be guided towards the LDR through this material special material and depending on the input voltage applied its intensity can be controlled.

[00:13:26]For very low voltage at the input, LED intensity will be very low. As we increase the input voltage, LED light intensity, emission light emitted light intensity will increase. And we know that initially at the dark phase, the LDR resistance is very high. Whenever some light or photons will uh incident on the LDR, it resistance will start to decrease. And depending on the uh intensity of the LED is modulated by means of the input voltage as I mentioned and that intensity will guide to change the resistance of the LDL. Okay. uh that means u ultimately at the output port these two ports are the resistance terminal which can be used to connect at any branch of the your of your circuit where the resistance tuning is required.

[00:14:24]Okay. So by changing the input voltage you are changing the light intensity and that light intensity is changing the resistance and that tuned resistance is uh connected to your terminal where the resistance tuning is required. So it is the working principle it is very simple to understand. Now uh from the general perspective you may understand that how can we control the resistance range that means the uh minimum resistance up to maximum resistance which range of resistance we can vary.

[00:14:59]There are two parameters. One actually three parameters. Uh you you you know that the spectrum of um that means the uh relative response of this LDR uh is generally limited within the visible spectrum. Okay, visible spectrum means starting from the violet light up to the red light. So we have to use the visible LED here and depending on the color of the LED it response will be different.

[00:15:32]Okay. So that's why LED wavelength is one parameter by which we can choose the range. Next is the transparency of this special material. If you use very much transparent materials then most of the light uh sorry most of the emitted photons will not be absorbed here and reach the uh reach the LDR surface and that will lead to uh very low side resistance that means the very low resistance variation range will be in the lower side and if you use some translucent material so most of the photons will be absorbed here and very few will reach the LDR. So in that way we can uh we can achieve the resistance range in the higher higher values. Okay in the order of few hundred kiloohm to me.

[00:16:27]So this parameter that in the transparency or optical properties of this special material is another parameter by which we can choose the range of the output resistance. And the third parameter is the length of this spacer. We know that as we increase the length most of the light will propagate through this medium and uh a major portion of the light will be absorbed and depending on that the resistance range can be achieved. So again I am recapitulating three controlling parameters is there. One is the LED wavelength. Second is the optical property of the spacer material and third one is the length of the device.

[00:17:13]Now uh generally these five types of VCRs analog VCRs have been uh fabricated and tested. Okay. Now first of all I should justify why this device is called a programmable optically variable registers. I should justify their name.

[00:17:36]First of all, resistor because it is giving one resistance. Now optically variable because we are changing the resistance value by means of change uh changing the light intensity of the LED.

[00:17:48]Okay, that's why optical variable. Now programmable why programmable?

[00:17:53]Programmable means by using any microcontroller we can vary the input voltage and depending on the input voltage light intensity will be varied. Okay. So by writing a program in a microcontroller we can change by using the analog write command. I am giving one example. Uh suppose we are using the simple adino uno or nano. uh for that case uh in order to change the voltage output of a GPIO pin uh GPIO pin uh it is actually generating the PWM waveform. Okay. Uh so by varying the duty cycle of the PWM wave we can change the uh average value that means the analog voltage value at at an output of a GPIO pin. that GPIO pin should be connected to the anode terminal of the LED and the cathode terminal should be grounded. Okay. So variable analog voltage can be applied through an microcontroller by means of uh a code.

[00:19:01]Okay. So that's why uh this device can be controlled by using one uh microcontroller by means of a program or code. Okay. So that's it is that's why it is called the programmable. So uh the resistance variation here we can make it simply automated or or uh adjustable through the code or it it can be adaptable. It can be adaptive in nature depending on your requirement at any time of the operation of the circuit.

[00:19:34]Okay. So first of all the what are the types of the POVs we have tested uh air core POV that means in place of the spacer material we have used simple air.

[00:19:46]Okay. Next one is the HMG core. Hmg means the hot melt glue. It is very common material or common polymer which is used for the hot uh hot mel cr. uh that is a popular adhesive in order to fix some parts of uh so plastic parts or wooden parts even metal parts can be fixed by means of this adhesive which is trans not transparent it's translucive in nature okay third one is the epoxy ti2 nano composite epoxy means the transparent epoxy resin and this ti2 titanium dioxide uh nanop particles are mixed with the epoxy in order to tune its optical properties. As I mentioned it is the second parameter of controlling the resistance.

[00:20:39]Uh all of these three first three are having the circular cross-section but the fourth is the rectangular cross-section. We know that for the planner circuits rectangular cross-section is important in order to have compatibility with most of the planner circuit. That's why rectangular cross-section have also been constructed and tested. And the fifth one the DIP POV chips that means DIP means dual inline packaged. As we see in our laboratory most of the IC packages are DIP. Dual inline package means there pin pitch that means the separation between two pins of the IC is 2.54 mm. So those are called the dual inline package. Now first of all air and HMD code view here. Uh you see that there is a uh there is a simple u PVC type uh imposer at one end LED is mounted another end the LDR is mounted.

[00:21:46]It we have taken different lengths of that it is these are the uh uh air core.

[00:21:52]These are the HMD core. HMD means as I mentioned that polymer core and those are tested dimensions are given in this table which are uh very important and thing is that by varying the input voltage known input within the known input voltage range the resistances are measured. Okay. And that resistance versus voltage characteristics as we see from this graph this red graphs and uh this the symbols these are signifying the um HMG core uh POV responses and these blue graphs are uh corresponding to the AR core uh responses. uh as I mentioned if you if you see at the resistance axis uh air core POV are having the sorry uh I have I have given you the just reverse information this red colored graphs are corresponding to the core POV and the blue color curves are corresponding to the uh HMD core POV okay so uh since The air is totally transparent in nature and very small amount of light will be absorbed within the air. That's why very low resistance range can be achieved by using the airports. Uh if you look at the resistance axis by changing the same amount of voltage, the resistance values are very low. But for the HMD core, uh as we increase the length, the resistance values are increasing. Okay.

[00:23:32]So that's why we can ch we can we can choose the range by changing the either the material inside or changing the length and these symbols are actually uh the square field square field circle field rectangle or star whatever these are the experimental values and the solid lines are representing one empirical formula which is car fitted with the experimental of experimentally measured RV characteristics and that card fitting is uh achieved within uh 2.5% of error. So that means uh for the resistances always we need to uh specify one particular parameter that is called the tolerance. Okay. Uh so in our device we have achieved 0 to plus minus 2.5 tolerance value which is much better than the commercial resistance tolerances which is either plus - 10 or plus - 5.

[00:24:41]These are the capacitance voltage characteristics which is also measured.

[00:24:44]We we obtain sub nanometer capacitors and it is it is very sharply changing with the voltage and since it is the subnanometer capacitance values and depending on the resistance value at which it is set the RC delay will be determined and we have uh checked that depending on the RC delay achieved by this PVR device it can be operate up to few MHz. Okay, that means uh it is it is moderately high frequency device, not very high frequency device.

[00:25:21]The third one is this one uh the temperature dependence of the resistance uh um with respect to the room temperature resistance. We observe that at uh if you use the air core resistance the resistance is highly dependent on the ambient temperature. But by using the HMD core um the resistance values are stabilizes after certain value almost 50° after 50°C. Okay. So air core POVs are not for high temperature applications but HMG core POVs are suitable for the high frequencies.

[00:26:08]Now epoxy ti2 nano composite core POVs.

[00:26:12]Uh for that epoxy is filled with some TiO2 nanop particles in order to modulate the optical properties of the special material. here in order to um in order to measure in order to measure the wavelength uh dependence of the resistance variation we have to use the RGB LED that means within a single LED both uh sorry three types of LEDs are mounted within a single LED package red R for red green for uh G for green and B for blue okay so it This one particular unit LED uh having four terminals. One is the ground terminal and other three terminals are corresponding to red, green and blue LEDs. By varying the voltage at this terminal the intensity of the red light will vary. This terminal uh the intensity of the green light will vary and this terminal intensity of the blue light will okay it is nothing but pixel of an LED TV or LED display which is capable of generating millions of colors by changing the input bias values uh in in different combinations. Okay, different intensities of this RGB um color will be emitted and in combination of those different colors can be um generated from it. Okay. And here within the structure uh this portion is filled with either pure epoxy. Pure epoxy is very transparent. So most of the light will reach the LDR surface. And if we if you do the pure epoxy by means of certain weight percentage of titanium dioxide nanoparticle then it transparency will decrease and as we increase the dosage value the transparency will decrease and decrease and we'll get in the resistance range at the higher values.

[00:28:22]So these are the fabricated structure as we see that uh the this one is the uh pure epoximate special structure which is almost transparent and ti2 weight% when it is.1 to5 weight% then it transparency is decreasing and as we increase the tio2% it transparency is decreased and finally This uh device should be colored with a uh that means it outer surface should be coated with some opaque color so that the ambient light cannot interfere with the inner operation. So uh here the nitro pigmented nitro paint is used to uh make this absorption layer in order to eliminate the ambient light interference.

[00:29:19]Uh these are the light propagation through the RGB light propagation. See that it is for only the red color LED, green and blue color LED.

[00:29:30]So RGB light propagation through the special structure for different POVs having different TiO2 concentration. So we can see that as we the as we increase the ti2 concentration light is reaching at light absorption is very high and it is capable of reaching not very far distance.

[00:29:55]These are the um dimensions of the of the fabricated POVs.

[00:30:03]These are the different sets of POV. See that this one is for pure epoxy core POVR having four different lens. This is for TIO2 weight percentage of.125 having four different lengths. In this way five different nanoparticle weight percentages have been used in order to form the uh total 1 2 3 4 5 and each are having the four different lengths. So 20 sets of UVRs have been fabricated and those are measured. So nano narrow spectrum source control narrow spectrum source control means whenever we used to control the resistance by means of a single colored LED either red or green or blue. Okay, it is called the narrow spectrum source control. Why? because single colored LED has a very small wavelength spectrum. So since the controlling LED is using a short spectrum or narrow spectrum that's why it is called a narrow spectrum source control. And now if we use simultaneously these three LEDs to control the resistance of the PVR simultaneous variation of R, G and B, it will it will cause to control the resistance by means of white spectrum.

[00:31:34]That means here the spectrums of red, green and blue are mared in order to control the resistance. Okay. So that is called the wide spectrum and first I am talking about the narrow spectrum source control but first the device structure is analyzed and a an analytical model have been established depending on the geometry of the structure wavelength uh uh sorry the LDR material and many other parameters have involved within this analytical model and finally this one is one analytical model uh by which we can predict the resistance value depending on the input voltage. It is the input voltage before starting the resistance voltage characterization. We have first uh checked whether the nano composites are well prepared or not. the Kio2 nanop particles are well dispersed within the uh epoxy core or not by means of the field emission scanning electron microscopic and it is found very good dispersion. Another experiment was done by means of the XRD that means the X-ray defractometry and by means of X-ray defractometry we can found what are the anot phases are present within those nano nano composites um different phases of TIO2 are observed as we increase the concentration of TO2 these peaks associated with different phases are more pronounced and one thing is that since it is the cylindrical optical fiber structure that's why the TIO2 um field epoxy should have good optical properties like refractive index absorption coefficient etc those are also measured in order to fill the analytical model.

[00:33:49]Uh finally this one is the arrangement to measure the resistance voltage characteristics and these are the resistance voltage characteristics of those all five POVs all sorry not five sets of POVs each having four length POVs that's why total 20 PVs okay so here the observation is that whenever we want to use low range resistance then the red colored LED source or red control of the PVR is the most suitable.

[00:34:27]Next is that whenever we want to achieve very high resistance range then the blue color LED is the most suitable one and if you want to uh vary the resistance with very high resolution then green color regist green color LED is the most suitable green color LED by using the green color LED we are achieving highest resolution because uh the LDR response have the peak at the green wavelength that means the four uh sorry 540 nanometer it is the wavelength corresponding to the green color source and at that wavelength maximum responsibility is achieved at the LDR that's why the sensitivity of LDR at green light is highest and that's why the highest resolution tuning is achievable by means of the green color tuning or the green LED uh control. Wide spectrum source control as I mentioned when three sources are uh varied simultaneously at that at that case we have modeled our LDR as a parallel combination of three different conductances and these are mutually isolated. First conductance is corresponding to the red light. Second conductance is corresponding to green and third one is corresponding to the blue light. And by using the analytical formula for single colored uh conductances and finally adding them uh into in order to form one overall conductance. we can model the resistance or the conductance of the POVR for the wide spectrum source control when the three different LEDs are operated simultaneously.

[00:36:30]Now again the this simultaneous LED control have been u used to measure the resistance variation for different modes and we have achieved um here see that these are the three dimensional plots because the input variables are now three input variables are there okay one is the voltage across the red LED voltage across the green LED and voltage across the blue LED and depending on the size and color of the uh these this circles we can we can interpret the value of the resistance. Uh so the these are by by using the wide spectrum source control or simultaneous control of the RGB LED we can achieve much more wider range of the resistance.

[00:37:26]This is the summary of the entire investigation and these are the achieved minimum and maximum resistance values for different devices having the different special lengths and different uh pi2 feedback concentration in the uh special material.

[00:37:46]As I mentioned uh in the first phase, there is an there is an uh compatibility issue with the modern day electronic PCBs where the circular cross-section devices are not compatible. Okay, these are see that these are the circular cross-section devices.

[00:38:07]These are not compatible with the modern day uh two-dimensional or multi-dimensional PCBs. That's why we have to fabricate these POVs uh in the planner form or the rectangular cross-section. I should show you that I will not discuss in detail the rectangular cross-section P here. These are the rectangular cross-section P here. Very simple. Just change the um cross-section of the enclosure from the circular to uh rectangular. That will give you the rectangular cross-section PR. And next one is the DIP PUBr dual inline packaged just like the IC packaging. We'll have packaged the POVRs by means of uh DIP packages. See there is one DIP chip containing dual POV.

[00:39:00]That means within this IC two POVs are present. Within this ICU uh three POVs are present etc. uh by means by by integrating multiple number of UVs within a single chip we can achieve uh these three IP packages. So development was started from this one that means uh simple transluten core POVR up to the TIO2 epoxy nano composite PVR and finally we have achieved GIP package PUVR which is ready to sell and ready to use for your uh applications for different sensor calibration application, robotic application etc. These ICs are ready to use.

[00:39:50]Now future work which is uh very relevant for the computer science students. Uh see for the PVRs uh whenever the source control is done by using the RGB LEDs three variables are present red, green and blue. Okay.

[00:40:09]Corresponding voltages and corresponding voltages. Other two parameters are the tiio2 loading and the spacer lens. Okay.

[00:40:17]If you consider these five as input parameters often neural network as per your choice whatever the type of the neural network uh the anyone can choose it and the output of the particular network model will be the resistance value. Okay.

[00:40:39]First experimentally measure this input output uh resistance values by means by changing these input uh variables and make a data set and divide that huge data set by means of two portions. One is the 70% used for the training and 30% used for the uh validation and after that train the model after training the model just validate by means of the 30% data set that mean disjoint data set and after that whenever this train model is uh available that train model can be used to uh predict any resistance value depending on the choice of uh choice of the input parameter. That means for the electronic circuits when we do require a particular resistance value to be applied to a particular branch then this resistance value will be considered as a target resistance value and depending on the target this neural network model will predict what are the input sets to be applied at the input of the PVR set so that the target resistance can be precisely achieved. Okay. And that can be made totally automated and replace the analytical modeling because as I show you in previously analytical model will give you plus minus 2.5% of error and we are now uh using the neural network models in order to reduce that uh reduce that particular error uh margin below below 1%. Okay.

[00:42:32]So applications of POV I'll just show you some applications. You can easily apply these POVs to any other electronic circuits where the resistance modulation is required. One is the 20 notch filter which is very important for the biomedical applications in order to eliminate the power line interference at the 50 Hz. Okay. So this particular notch filter is used for eliminating the low frequency uh very low frequency noises from the ECG, EEG or this kind of uh biomedical sensing or data acquisition systems.

[00:43:15]Here uh this is the 20 20 circuit but three resistances are used and three capacitors are used in place of the fixed value resistances we have used POVs in order to uh change those by means of external voltages. Okay. So if you able to tune those resistances to particular values so that the notch frequency can be precisely tuned. Okay.

[00:43:42]If you show the results, we have perfectly tuned the NOS frequencies to 20 Hz, 50 Hz, 100 Hz and 200 Hz etc. These are the magnitude response and these are the phase responses. And those uh experimentally obtained values are perfectly matched with the analytically obtained values. analytical optain values are actually generated from circuit simulation tool like P spice can spice etc. So uh these are achieved very precisely.

[00:44:19]Second application is the programmable optically variable potentiometer. As I mentioned in the previous uh at the first slide the potentiometers are the uh very commonly used mechanical uh variable resistance. By changing the uh whipper by by changing the position of the whipper we can change the both side resistance values in order to form a uh uh potential divider circuit. So by using two parallelly connected POVs we can achieve this operation and this one is that application. See there is a microcontroller ESP32 which is controlling the input voltage of the P input voltage of the QB by means of the filters. These are the low pass filters by which we are converting the PWM waveform to equivalent DC uh voltages.

[00:45:13]Okay. And that DC voltage is applied to the input LED side of the PVR. And depending on the uh um voltage value uh coded here, voltage value applied here within this GPIO, we can change the intensity of the light and adequate resistance can be achieved here. Okay, which is applied to the two terminals of the uh two two PUB gears are there which are controlled by means of these two GPIOs and depending on that R1 and R2 at the output terminals will be achieved.

[00:45:46]So these are the characteristics resistance voltage characteristics of one side is showing as the blue graphs other side is showing as the red graphs and these are the residues of uh the resistance values with respect to the analytical model and here we have achieved lower than 1% of error. Okay, which was our target uh in order to reduce the error.

[00:46:14]Third is the automated transistor biasing circuit. We know that for the fixed bias circuits or potential bias circuits four resistances are values are very important for uh biasing a particular transistor in order to achieve suppose amplifier application or switch application whatever uh the resistance values are very important. Most of the cases fixed value resistors fixed value resistances having very uh high tolerance values are not sufficient to achieve very precisely control gain of the amplifier. That's why POVRs are used in place of the fixed value registers. uh and it is controlled by a microcontroller seo and we can achieve very u very good u precision of um conditional viing whatever. So this one GP GUI graphical user interface which was uh controlled from an machine or PC uh by using the user user will just input the resistance values and u controller will calculate what should be the input uh voltages to be applied at the input of the PPR so that these resistance values can be um achieved in the transistor wing circuit. And depending on those the measurements will be automatically done and it will show you the condition characteristics as well as the biasing analysis and your operating point. Okay. So GUI is prepared in order to perform the automated transistor biasing in in with uh these are few applications as I I have shown you that students are also working on various other applications like inverting non-inverting amplifier circuits uh having variable gains or differential amplifier circuit having uh variable gains etc. uh by means of POVs. Okay. So I am not going through the conclusions.

[00:48:28]Uh this work is still going on. So it is not time to conclude. You can also contribute your uh knowledge to this particular field in order to achieve uh uh different types of UVs or more applications you can try. These are the list of publications references. Thank you. Uh is there any question from the uh now I'm welcoming the question from the uh viewers end. Is there any question?

[00:49:05]Yeah.

[00:49:14]Uh u actually programmable variable register most important application is the selzer calibration most important application. Okay. And uh particularly where the intensity modulated sensors where the voltage output value is important. Okay.

[00:49:37]In those cases, the POV is the most important.

[00:49:52]Yeah. Uh if you want to uh suppose you want to as I mentioned one thing the AI can be used to uh model the POV also. Okay, that means in better way in place of that analytical model. Another thing we have to think about what are the applications where suppose you want to uh you want to make one circuitry. Okay, large circuitry where by which you can uh physically uh make one neural network. Okay, in those case those weights can be modulated by means of the resistance values or some potential divider circuits. Okay, for those cases multiple POVs more than hundreds or 200s can be used uh for for realizing large neural networks in hardware.

[00:50:56]Thank you.

[00:50:59]Yeah.

[00:51:00]Yeah. Yeah. Yeah. Sure. Sure.

[00:51:08]Yeah. Yeah. Yeah.

[00:51:16]Yeah. Yeah. Actually uh the uh absorption loss, coupling loss uh and all optical losses like the scattering etc. uh we have to take into account. Okay.

[00:51:29]But the dialectric loss is associated with the uh electric field or magnetic field whatever it is not associated with that. Uh we are talking about only the optical losses. Okay. So those has to be uh included in our model. Those have been included.

[00:51:52]Thank you.

[00:51:58]Thank you.

[00:52:28]Thank you.

[00:52:30]Thanks to everyone.

[00:52:45]>> Thank you. Thank you. Thank you, sir.

[00:52:48]>> Thank you.