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Embedded Systems and Design & Development - Feb 18, 2026 | Afternoon | VisionAstraa EV Academy

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Core Theme

This content explains the process of measuring physical parameters like current and temperature using sensors and converting their readings into usable data for embedded systems, focusing on the practical implementation and challenges.

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>> Yes, thanks for confirming. Uh we will

just have a recap of uh what we have

been discussing in yesterday's afternoon

session. then we will continue with uh

today's topic. So we have been in the

after today's session yesterday

we have been discussing about the

different kinds of current sensors and

which are the possible candidates which

are the possible sensors which can

probably used in a EV environment. So we

have uh just reviewed the current

sensors which are uh coming under the

type of shunt resistor sense resistors.

Then hall effect based current sensors

then we uh reviewed the current sensors

uh current transformer based current

sensors. Then the newer version of the I

mean sophisticated current sensors which

are referred as flux gate current

sensors and magneto resistive current

sensors. When it comes to the

sense resistor, shunt resistor based uh

current resistor, we install

a resistor in series with the load so as

to create a voltage drop and thereby

measure this voltage drop in order to

assess what is the magnitude of current

flowing into the load. This is the

simplest of all methods and it in in a

way is the cheapest of all methods. So

this uh apart from this method the one

which is frequently used is all effect

based sensors and the third category is

third type is the current sensor current

transformer based current sensors. Now

out of the three which has been listed

on the top we have seen that the first

two can be used for both AC and DC

currents whereas the third one the

current transformer based current sensor

it can be used for measuring AC currents

alone. Obviously it is a transformer

which requires a varying field. So it

can be used only for measuring

AC currents.

Now a typical current sensor will have

the resistor placed in between. We will

talk a little bit more about uh these uh

series resistors. What kind of uh design

calculations you probably will be end up

doing when you're going for this kind of

method. And of course uh we will be

seeing uh certain other things uh

related to these uh sense resistors

current sense resistor based methods and

before that we will yeah I think that

should be enough for the recap. Now

coming to the main question. So now we

have uh amount of current to be

measured. Let us say it is a maximum of

1 amp current that should be measured. A

load any it can be any load. It can be

EV motor or it can be the charge current

getting into the battery or it can be

the discharge current or it may be the

current consumed by any other auxiliary

systems. Anyone let us take any one of

these systems. We want to have

assessment about how much current is

flowing into the load into one of these

kinds of loads. So under these

situations assuming that we have

selected current sense resistor type in

order to get assessment of the current

then what are the procedures which we'll

be going into that we will try to have a

review of that. So

let's say that we have a a source let us

just represent it something like this

and this particular source is connected

to some load. Let us keep this generic

and so we will use the generic symbol a

rectangular box to represent some load.

It can be any load. Now we will have

some quantification of this source and

load side. Let us say we will take a

even figure. We will say this is uh 10

volt source and on the other side we

have say uh we will keep this also 10

ohm. So under this particular case we

can assess that 1 ampere of current will

be flowing through it. So we know from

these things if at all there is a chance

that this resistor can vary. Let us say

this is going to vary from say 10 ohms

to 100 ohm. Once again we will keep all

these figures at a whole number. So the

calculations will be easy. So this

particular resistance of the load let us

assume it is can vary from 10 ohms to

100 ohms. So in this particular case the

current which can be supplied by this

particular source will vary from 1

ampere to.1 ampere. So we are just

making use of ohms law v is equal to I

relation same thing we have been using

compute this particular range. Now when

we have the necessity to know or our

embedded controller has the necessity

know what amount of current is flowing

through it. So in order to take some

protective measures or in order to take

a control measure if the embedded

controller wants to know that then this

current parameter is incompatible with

the ADCs what we have. So remember

whatever ADCs which we are talking about

yesterday those are able to measure only

voltage variations. So now we have

current which is varying that need to be

measured. So this is where conversion of

the current parameter into voltage

parameter is required. the type has to

be converted. So in order to convert

this current into voltage, we are going

to break this circuit somewhere here and

we are going to insert series

resistance. So this is going to act as a

sense resistor. So depending upon the

amount of current flowing through this

particular resistor, a voltage drop is

going to be created. Once again, it is

based upon Ohm's law. This particular

wtage is your sense wtage. Now once you

have converted the voltage into current

into voltage you can very well measure

this voltage by using your uh ADC of

course after making it compatible with

the ADC input levels. So let us go with

0 to 5 volt range ADC. So this is your

ADC output digital. So this particular

digital data is going to be processed by

our microcontroller and then you're

going to assume you're going to take

some decisions. Now in this particular

process you will be interested in the

first uh step you will be interested in

determining the value of current flowing

through or the value of the resistance

sense resistance which need to be

installed here. So what the sense

resistors value should be this we have

to figure it out. So when we are

selecting it we will be keeping certain

things in mind. The first thing is once

this voltage drop is getting created, we

have to make sure that it doesn't pass

more than 5 volts. The maximum voltage

that can be accepted by our ADCs. So we

have to make sure that the maximum

current of 1 ampere when flowing through

this sense resistor R sense it is

creating a drop of 5 volts. So naturally

we can once again use Ohm's law. We can

apply that the maximum voltage is five

that is required. The maximum current

that can flow through is 1 ampere. So we

have taken all these figures from the

specifications we have framed earlier.

This voltage this current this is a

maximum current flow flowing through the

resistance. When it is flowing through

the maximum voltage that is permitted

the drop that can be created is 5 volts.

So this using this one slow ohm once

again we are going to get a figure of 5

ohm. So now this is in this particular

case we won't be going for a 5 ohm

resistor for uh various reasons that we

will be discussing it shortly. So let us

go with this 5 ohms resistor for now. So

once we have selected the value of this

arson resistor we are going to install

it in series and then we are going to

create a drop that is going to be

measured by our CPU and the control

decision is to be taken. Now there are

few aspects which we have to watch very

carefully when we are giving the first

thing about is the electrical connection.

connection.

So when you are providing voltage to

this ADC terminal, you will be supplying

it with respect to the ground. Whatever

voltage which is being applied here,

that will be applied with respect to the

ADC's ground terminal. So when you're

doing so, you have to be careful where

you are going to place this sense

resistor. So if you place it in any

other circuit place like this, maybe

something like this. Now this creates a

problem. So yesterday we were talking

about the floating terminals. So the

reference terminal will be floating. It

won't be having the reference potential

of zero. It'll be having some other

potential which means that your ADC will

not be able to do its job properly. It

has to be supplied with the voltage here

to the input terminal. In our Ardino

Uno, we had A to A6. Similarly, you will

have ADC input terminals. So this is

your ADC input terminal. With respect to

this terminal, we have to measure the

voltage at A. So the other end should be

having preferably having zero potential.

So this is related to the connection. So

let us say we have

installed the

the resistor and in this particular way.

So here you see that there is a 0 volt

potential. This is supposed to be the

negative terminal. We will call this as

a reference terminal. So with respect to

this reference the potential at this

point is taken. So now you won't have

any problem with your ADC measurement.

So this is about the connection. So

first aspect what you have looked into

is the connection aspect. The location

where you are going to install the

Right? What will be the next thing? Now

we are getting the information about the

voltage present on this ADC.

Once again recolct your ADC is the one

which measures the input voltage. It is

analog to digital converter which

samples only whatever uh ADC peripheral

which you have on a microcontroller. It

just senses the voltage variations. What

we are actually interested is in the

current variations. So you need to first

to find out the relation between the

current in this case we will call this

as load current whatever current which

was which is flowing through it this one

you need to find the relation between

this load current and the voltage

produced across this sense resistor so

if you are able to get a relation then

it'll be easily possible for you to

correlate it for instance if at all your

ADC output the digital outputs what you

are having here that is assessed to be 5 volts.

volts.

Fine your CPU has find found out that

the ADC is sampling 5 volt magnitude of

voltage. Now from this you have to infer

you in the sense the embedded controller

has to infer that this X amount of

current is flowing through it. Now this

is what we are talking about. How are we

supposed to get our idea about what is

the actual current flowing through the

load? In order to take take a decision

whether to sense it as a overurren or

whether to make some control aspects we

need this information. So how do we get

it? Once again by formulating a

relationship between these two

parameters. So in this case we clearly

know that a 5 volt will be produced by 1

ampere current. So this particular

relation is very important for the

design engineer to know. Why? Because he

has to write a program which is going to

end up inside a microcontroller's flash

memory and which in turn is going to

take these control and protective

decisions. So in this context the

relation between the current and voltage

in this particular case one parameter

and the other parameter it is required

to be found. The very easy way of doing

it is to either tableate the readings

and find out the relation or to map

these values and find out these

relations. So let us try to use the

second method in this particular case.

So well let us say so we have mapped all

these values. So when we will put the

current on the x-axis and the voltage on

the y-axis. So now when the current is

let us say this is one when the current

is 1 ampere

the voltage will be five. In the same

way when the current is say uh 8 we will

take some discrete steps 6 4 and2 under

these particular cases what will be the

we are assuming a linear relationship.

So this we have found out. So now you

have an idea about

what wtage will be created when this

current is flowing or when this amount

of current is flowing. This relation you

can invert it and you can use this to

find out a relation something like this.

Y is equal to MX + C. See all of these

points if you relate it you will have a

straight plane like this. So in this

case we don't have any C. So we don't

have to bother. All you need to do is

find out the value of M. So in this

particular case what m is going to be

you're going to take the delta value on

x and y axis at any particular instant

you can take either this delta or the

delta as a whole or this delta or this

delta anywhere since it is a linear line

it is a straight line a linear

characteristics what we are having at

least what we are assuming to have this

relation is going to be y= mx plus c. So

that makes it perfectly valid to take a

relation like this 0 to 1 ampere then 0

to 5 ampere. So I'm going to take the

entire range. So 1 - 0 sorry 5 - 0 on

the yaxis 1 - 0. So naturally 5 is going

to be the m value. Now you have got

yourself a characteristics equation. Y =

5x. So what is y here? You have to uh

remember you shouldn't forget that y

axis you have the voltage and on the

x-axis you have the current. So now if

at all I give one of these parameters

you will be able to find out the other

parameter. Let us say the voltage which

is sensed now has to be has been found

like this. Let us say uh y is equal to

the ADC has sensed some voltage and this

voltage happens to be 3 volt. Now using

this relation whatever you have

formulated this particular relation you

will be able to find out what will be

the x value that is the current value.

So 3 by 5 that obviously should give you

this particular value of 6. So this is

how you use these characteristics

equation in order to find out what

current is actually flowing through this

particular load. Now this equation is

exactly the one which you have to

convert it into a code and then put it

inside your embedded controller for

taking control decisions. Suppose this

this particular process you have some

clarity on it.

Where is my mouse?

Yes, it is here.

Okay fine. So this uh maybe you from

your side you can try doing one more

calculation. Assume this particular ADC

now has

detected a voltage of say 4 volts. Now

can you figure out what is the current

flowing through

the resistor? What actually is the load current?

You can use the graph information on the

graph or best is to use the relation

Now the thing which you are required to

do is find out what is load current that

is what is x value when y value is four.

Yeah, wonderful. That is8 amp. That's

that's exactly how you use these

relations, how you exploit these kinds

of uh data in order to take a control decision.

decision.

Okay. So this process is uh uh same the

process what you have uh uh just now did

it is uh uh similar for uh converting

any data whether you are measuring the

temperature and converting into a

voltage using your transducers or even

if it is a high voltage which you are

measuring uh through your ADC if you are

measuring the high voltage by processing

the voltage by conditioning the voltage

you can correlate it and then you can

find out the actual magnitude of the

parameter which you're trying to

measure. For instance, yesterday we were

talking about a 9V battery and we saw

what is a conversion ratio which is

required for the potential divider. In

that manner, you can perform these

calculations to get an idea about the

actual parameters magnitude. Now this is

one thing which we have to keep in mind

very clearly.

So this relation so whatever relation

which you saw here you need to

you need to remember how we have

formulated it. So once again let us

recollect it because this is one of the

core concepts for you to uh decide on

the value which goes into your program.

So once again we will try to recollect

what is a process we have formulated.

You look into the input parameter this

side and the output parameter. So as

long as the ADZ is concerned, the input

is voltage, output is digital. That is

not what we are talking about. We are

talking about the actual physical

parameter which we are measuring. The

physical parameter in this case we are

measuring is the current that is a load

current in this case. And the output of

the circuit which is measuring this

parameter that is the current sensors

output is the voltage. So this is what

we have to use to plot the relation and

get a relationship equation between

these two parameters. So we consider

this I as independent parameter. So we

have been doing this for a long in

dependent parameter we put it on the

x-axis. Independent parameter we put it

on the y-axis. The same concept here

also we will mention the independent

parameter on the x-axis and the

dependent parameter on the y-axis. So

once we have represented these uh

parameters we will start measuring what

is the output that you'll be getting for

a corresponding input. If at all the

current is 0.25 what will be the

voltage? If at all the current is 6 what

will be the voltage? We try to get this

relationship in the form of a table.

Then from the table we plot this or

directly from the table also we can from

a relation like this. So in this case we

have plotted the relation so that our

understanding will be very clear. So

once we have formulated a relation this

uh I mean we have plotted this

particular relation we have observed

that this relation is linear. So most of

the practical cases this relation will

not be linear. So in our forthcoming

discussions while we are talking about

temperature sensors you will clearly see

that the relationship between the

temperature and the transducer output is

always nonlinear kind of nonlinear most

of the times. So that time we will be

discussing more on this relation linear

nonlinearity uh relation. So in this

case the relation between the output

wtage and the input current is linear.

So using this linearity we have

characterized this plot in the form of a

straight line characteristics that is y=

mx + c. There is no offset. So we have

scratched out c. And then after that we

try to find out the value of the slope

that is m. Once we have found it out by

using the delta y delta x method, we use

this as a characteristic equation to

write our algorithm. Now this equation

is the one which is going to go sit in

your embedded program for doing all

these decisions in order to compute what

is a actual current flowing through it

or the actual voltage or perhaps any

other actual parameters value. So once

you get to know this, it'll be easy for

you to mention this inside a conditional

statement. If at all the current flowing

through is more than 1 ampere then cut

off the supply. If at all the current is

0.5 increase the current supply. These

are the control decisions that are to be

taken. In order for these control

decisions to be taken once again let us

reiterate the formulating these

relations are very very important. So

having an idea about this we will move further.

further.

I'll just pass on a couple of uh uh

minutes or so so that this concept we

will make sure that we have understood

anything. If you have any doubt you can

Yes, some of you have asked about uh the

OPM circuit explanations. Uh as of now

let's uh skip that. This is actually a

amplifier circuit feedback amplifier

circuit. So these kinds of amplifier

circuits are used to amplify the voltage

and right at this point you might be

asking the question why signal

amplification is required. We will

answer that shortly.

So if I hope this particular uh point is

clear how a relationship between the

input and output uh sorry

where is it? Yes the laser point how a

relationship between the input and

output parameter is formulated. So once

you have got this idea clear we will go

Right. So now we will try to uh deal

with the answers related to why these

kinds of amplifier circuits are

required. Now I'm going to erase the

contents on the whiteboard. Yes.

Yes.

Now we will try to answer the question

related to this.

So we have figured out in that

from that diagram once again

I'll just represent this part of the

right? So we have found out in the

previous case when the voltage was 10

volts and the load was varying from 10

ohm to 100 ohm that the sense resistors

value which is required is 5.

Now let us try to compute what will be

the power compute consumed by this sense

resistor when the maximum current that

is 1 ampere current is flowing through.

So we are going to use once again the

relations what you have acquired in the

beginning of your engineering days or in

your uh high school days. So we are

going to use this. So this is a relation

which we normally use for computing the

power. So in this case the power loss

the power loss which is occurring in the

sense resistor. So I square R maximum

current that can be flowing through when

the resistance is 10 is 1 ampere. So we

are supposed to use this figure of

maximum current. So 1 ampere squared

multiplied by the resistance. So

resistance value arson value because we

are dealing with the power loss

occurring in the arson sense r hence

happens to be five. So this gives us

five watt as answer.

Now look at this. This particular figure

is very large. Five watts of power

electrical power which is supplied by

the source. it is getting wasted in this

sense resistor. Usually this wastage

happens in the form of heat. So you have

to expect high amount of heat being

dissipated in this resistor. So

specialized resistors which can handle

this amount of power is required. So the

rating of this resistor should be 5 ohm

and 5 watt. So which is going to be

significantly expensive. So now what we

can do in order to reduce this forget

about the cost. The wastage of power is

much. Why is it so? Because when that

amount of current is flowing through

this resistance least resistance, it

will be consuming the load will be

supposed to consume 10 watt. So half of

the load power is getting wasted in this

sense resistor. That is a really

unacceptable situation. This has to be

tackled. So how are we supposed to

tackle? Only by reducing this voltage.

we have to somehow reduce this sense

resistors power loss. So that can be

done if we reduce the current that will

happen when we reduce the resistance

value. Now assuming that in order to

keep this uh power under control power

loss under control we have selected a

resistance of say.1 ohm.

Usually we will be selecting resistance

which is less than 1 ohm. So current

sense resistors it will be usually be

selected so that it has a very less

resistance. So now we have taken just

for argument sake we have taken a value

of 0.1. Now I² R is this particular

figure it would have come drastically

but at the same time the drop which is

created across this resistance the

arson's resistance that would have also

come significantly. Now whatever

voltage which comes across this

sense resistor will be equal to just.1

volt. So this we have selected as 0.1

and this is 1 amp current. So that is

going to give you just.1 volt. This is

very very less. You have to recolct that

the ADC what we have taken uh for

discussion it can handle a maximum of 5

volt range. So now the full scale value

is 5 volts but we are just measuring

currents from or voltage from 0 to.1

volt which is going to be very difficult

for this ADC to give a reasonable

output. The resolution is going to be or

the accuracy is going to be affected

drastically. Now this situation once

again is unacceptable unacceptable just

like the power loss situation is

unacceptable. This also is not

acceptable. we have to compromise on the

accuracy of the data which we are trying

to measure. So in order to cope up for

that we have to amplify this signal and

that is precisely where these kinds of

amplifiers comes into picture. So we

have to make sure first thing we have to

make sure the ADC terminal is not input

ADC ADC terminals input is not getting

loaded. Next thing we have to make sure

this amplification also is done. So you

combine the instrumentation amplifiers

with these kinds of magnitude amplifiers

and then you feed in the signal to your

see here they have mentioned then you

feed it to your ADC input terminals.

This way we compensate for the accuracy

loss which happens because of the

reduced selection of reduced value of

arson resistor. I hope uh that answers

that query which we had earlier why

these kinds of amplifiers are required.

This is a negative feedback. You would

have studied that negative feedback

amplifiers are much more stable. So the

same thing similar kind of thing are

being employed here. And every such

sensor uh uh sensors whatever you have

in the form of a packages IC packages or

a similar kind of board based solutions

by default the manufacturers of these

IC's or the boards sensing boards they

would have incorporated these measures.

In addition to amplification, you will

also see noise suppression mechanisms

that will come by default along with the

board solutions. If at all we are

designing as a custommade solution, then

at that time we will be keeping track of

designing these elements then testing

these elements before we deploy these

kinds of custommade sensors. So that is

a different uh that doesn't come under

the perview of our discussions right

now. So we will stop our discussions

Right? So similar kind of principle can

be applied for the other kinds of uh

current sensors. You need to first of

all find out the relation between the

sensed parameter and the ADC input

wtage. The output wtage and the input

sensed parameter. So in this case it is

current. We have to formulate a

relation. That is the very most

important point. Once you got a

relation, then decide using this value

for making any control decisions. That

is going to be much easier

Okay. With that we will uh conclude the

review and uh extended discussions on

current transformers. Maybe one small

task you can try it for today. What you

can do is let us assume you are going

for a short circuit protection in your

in your uh in your batteries. Let us say

your battery cell. We will once again

take it as a cell just for uh uh

experience sake. So assume it is your

same old lithium ion cell. I have

represented the symbol of a battery.

I'll convert it into a cell symbol. Yes.

So now we have

a cell. So this particular cell is being

charged or discharged. It is being

subjected by using some converter

circuit. So we are going to install a

current sensor somewhere. This is not

the ideal location. Already I have told

you we are going to install a current sensor

sensor

at appropriate location

and you are going to just assume that

this conversion is already happening.

You can use Tinkercad and the block

based code development logic or the text

based code development uh uh mode you

can use this now you just maybe later

today evening or uh today night you can

try this logic if at all the current

sensed uh by this current sense resistor

is say we will use the same calculations

is beyond 1 ampere you can try making

the built-in NE

built-in LED should be on if the current

is less if it is staying within the safe

levels let us say there is no visual

indications this built-in LED is off so

this same logic can be used later on to

isolate the battery just now just like

yesterday how we have been isolating

looking into the circuit which is used

to isolate the battery under over

voltage conditions this let us say is

helping us to pro prevent over current

or short circuit conditions so this

logic you can try it all you have to do is

remember that we are using this current

parameter instead of voltage. You're

So just a few additional uh tips uh for

people who are exploring this Tinkercad

environment. If you need any information

further information about how to use

these elements or uh how to wire up

these elements, you just have to use the

help context of these things. For

instance, uh most often people tend to

get confused when they are using

external LEDs there. So, which is anode,

which is cathode. You can just move the

mouse cursor

along the terminals so that you will get

a description of the terminal names. So

in this particular case a diode will

have anode and cathode and anode will be

connected to positive potential or

higher potential cathode to lower

potential. So here you see this terminal

is your anode. So if at all you have

looked into the actual diode, you would

have seen that the terminal or the lead

which is having a shorter length that is

your anode and the other one is your

cathode. So even if you have any doubts

while you're making connections, you can

always uh tie it up to the potential

points and thereby you can verify it.

For instance, uh let us just say I'll

just use the same your favorite Arda

board. This is for just checking it in

case if you are trying to find out where

the error has happened or whether you

have done everything properly. So we

will just try to connect the uh LED to

the VCC and ground. So see this is your

cathode terminal. So this cathode

terminal is supposed to go to the low

potential point. So we have connected it

to ground. This is your anode potential.

This is anode terminal. This is supposed

to go to your high potential. So we have

connected it this way. This is going to

be your current sense. I mean current uh

limiting resistor. So 220 ohms, 330 ohm,

470, any one of these things. Depending

upon how brighter your LED should be,

you can use that value.

So once you have done that, you just

click on it. You should see that it is

working perfectly. So if at all it is

so while we are making connections we

were a little bit confused and we have

made connection like this. So you can always

always

debug your circuit by checking the

circuit's operation in its basic

configuration. So in this case it is not

working. So what you can do before if

your actual circuit is having some kind

of uh issues like this you can always go

back open up a new diagram new circuit

and then test your circuit element there

then come back here and make the

modifications. This is one thing you can

try and other thing which I have to

is regarding how you have to process the

ADC values. Just briefly we will look

into one of the example programs and

thereby we will look into it. Then we

will continue our discussions about

temperature sensors. We will take the

same example what we have seen yesterday.

yesterday.

In this particular case you look at the code.

code.

Now see this particular value

whatever your ADC is reading and which

is getting stored in the ADC registers

that is the memory locations

corresponding to the storage of ADC data

that data will be

the actual uh uh ADC data in this case I

think it is a 10 bit ADC what you have

in ATmega 328 so it will be two or 10

you will have a maximum of 0 up to 1 0

23 data. So that is a value you will be

seeing for this particular variable this

sensor value variable. So this is the

actual digital value that you are

looking into your analog read function

in this particular case. It reads the

data from your ADC module. Whatever

voltage which you have on the ADC input

that is getting converted into digital

data, isn't it? That digital data is

what you visualize in the form of

integer number.

So for instance, if you have two bits 0

or 01, you represent in integer as 0 or

1. Or if you have 111 you represent it

as seven binary information 101 you

represent in the integer as 5 volts. So

whatever value which we are seeing here

in the sensor value variable that is the

integer representation of the digital

data. So this you have to very clearly

keep in mind while you are trying to

experiment with your own programs. If

you directly write 3 volts or two volts

here then you won't be able to get the

uh idea properly. Maybe I'll just uh

momentarily show you what I actually mean.

mean.

Once again, you're going to plot the

relation between the

the

input and output. In this particular

case, your input is going to be the ADC voltage

voltage

up to 5 volts and the output is going to

be 2^ 10 states that is going to be

1024. So we will consider zero also as

one of the number or even if you

represent it as 1023 nothing is wrong

you have a slight error but that is

tolerable and listen otherwise we are

wired for perfection we don't have to

really bother too much about these

things now the relation between these

two has to be found out in the same way

what you did in the previous example you

have to find the relation between this y

and x so you essentially are going to

find out the slope so the slope you can

take delta y and delta x or you can

consider the entire duration. So here we

are going to do the same thing like the

previous case dy

dy is 1 0 2 3 - 0 and then 5 - 0. So

this is going to give you information

about this slope. So I have told you

yesterday how to compute the resolution

isn't it? So we have 10 bit resolution

from our ADC of AT at mega 328. So this

particular information gives you uh

information about the accuracy with

which we can measure the input. So

simply to put 1 by two power whatever

number of resolution bits you have that

is going to be your accuracy. I think

yesterday you gave me the answer

somewhere around 1.2 m volts or

something 1 m volts approximately. So

this is a resolution with which you can

measure the change in the inputs.

This point is the one which you have to

remember while you are making these

kinds of calculations and while you're

writing programs accordingly. So in this

case where you have 5 volts you'll be

using it like this 5 volts is divided

into two power 10 states. So whatever

value you are getting that is going to

be the minimum voltage that you can

variation that you can measure. So keep

this in mind and use it appropriately

while you are writing your programs

maybe today evening or tomorrow I mean

So the next aspect when it comes to

monitoring is thermal management.

Yes. Uh if you have any queries

regarding the discussions we had until

Yes, if you want to practice in

Tinkercat, you can of course practice.

But uh if you take it as a homework

also, it will be good.

So we will try to uh cover as many

aspects of BMS in this uh week. Maybe

tomorrow morning session, evening

session, then uh Friday morning I won't

be available after session.

So in the fourthcoming sessions we can

expect to uh hear the discussions about

the control aspects. So far we have been

monitoring the parameters. Now we have

to make use of these informations to

take control decisions and protective

decisions. So that will start from

computation of state of charge and state

of health if we have time and use how to

use this information for protective

purposes or uh for controlling the

charge discharge processes. We will be

discussing about these things. Primarily

we'll be discussing about the algorithms

and how to translate these algorithms

into codes and uh uh to a certain extent

we will see a brief demo of the hil

which you can possibly employ in testing

FBMS or in uh creating of your

uh your own projects the hardware in

loop or simulations. So we will have a

hardware running our program every other

things the input and outputs we can have

it as a simulated input and output. So

these kinds of things there are

different kinds of similar kind of uh

simulations. You have something called

as apart from hardware and loop

simulations hil you have something

called as uh processor and loop you have

something called as software and loop.

You have different kind of loop

simulations. We will just try to see the

hardware and loop type of simulations

which will help us to debug and uh

develop the programs in a minimal number

Okay, I think we can proceed on to the

Right. So, we have seen what are the

different methods we can possibly employ

or different sensors we can possibly

employ to measure voltage and current.

Now we need to know also about the

different types of sensors available for

measuring the temperatures. And out of

these available sensor types, which uh

category of sensors or which type of

sensors is apt to be used in battery

management systems or to measure the

traction inverters temperature or

traction motors temperature most of all

important the battery and the traction

motors most two important um places

locations where you have to keep

monitoring the temperature in order to

safeguard the safety of the equipment

and moreover safety of the operating

personnel. The temperature at these

locations has to be monitored. It is one

of the critical things we have to do. So

before that we need to know what are the

different sensors available different

types of temperature sensors. We would

have learned uh probably in your second

year or somewhere the different types of

sensors you would have got introduced to

at least you would have heard

thermouples, RTDs, thermisters,

different kinds of things. So we will

review these different types of

temperature sensors available. Then we

will see which sensors are primarily

used in automative areas the ones which

are applied to automative sector and

then we will take our discussions from

So we have uh the conventional uh

thermister RTD kind of thing and we do

have certain other things. Some of those

things which are primarily or uh widely

which are being employed that we have

listed it here. Starting from the then

going to the RTDs resistance temperature

detectors then the semiconductor based

IC sensors what you have in the form of

a package. Then you have the non-cont

type. All the first three whatever you

are seeing those are uh these three

they are contact type. The sensor has to

make contact with the surface or the uh

area where the temperature has to be

measured. So when you have the necessity

of making a non-cont type measurement

then you will be employing sensors like

this infrared. You know everybody which

is having heat it emits infrared lights.

So your infrared sensors measures these

infrared light intensity and then it

godes the temperature of that particular

body or that particular point location

which you are interested in measuring

the temperature. Then apart from that

you would have also heard about

thermouples and fiber optic

temperatures. So these two things we are

going to keep it out. So only when we

are looking at measuring very high

temperatures we will be looking into

thermouples which may not be required

for discussion for EVT automative

related applications and once again

fiber optic transers when you need

isolation people tend to go for these

also it gives a wonderful accuracy the

noise rejection or the noisefree

environment with which the measurement

can be taken that is wonderful with

these kinds of temperature sensors but

costly because of that we don't see

these kinds of things in regular

automative uh applications unless and

otherwise people are dealing with R&D

related uh tasks. So we will stick to

the discussion of the first four sensors

which we have.

Okay, it's uh 2:50. If you want we can

have a break of 10 minutes and we will

or like yesterday we can continue and

then we can finish earlier.

Let me know whichever is preferable for you.

you.

If you want to have a break or uh if you

Okay. Right. That would be fine. So just

like yesterday we will continue and we

will wind up right.

Okay. Most of you have uh asked to

continue. We will continue it. We will

continue it and whatever. Yes. Yes.

Please we will continue. Yes. Right. Now

coming to the discussions about the

thermostats. we have uh we can actually

we can actually understand the working

of these thermisters by looking into the

word itself. So if you split it up you

will end up getting the idea about the

working principles of these thermisters.

These are basically thermal resistors.

So resistors are the ones which uh uh

provide resistance for the flow of

current. In a similar way these kinds of

thermisters resistance that varies

depending upon the temperature which is

it is subjected to. So whenever the

temperature varies the resistance also

varies. We can simply remember

thermister's operating principle like

this. Now when it comes to thermisters

you have two different types one called

as NTZ and PTC. So what PTZ and NTZ

stands for? I think in the beginning of

the classes in this week we have talked

about PTZs positive temperature

coefficient it's uh referred as positive

coefficient. So what it actually means

is the resistance increases as the

temperature increases. That is the

meaning of this PTC. On the other hand,

negative temperature coefficient means when

when the temperature increases then

resistance decreases. So we have both

the kinds of types available in this

category thermister category PTC and NDC

positive temperature coefficient and

negative temperature coefficient.

depending upon the requirement for that

particular area for that particular

application we are supposed to select

one of these types of transducers. Now

the characteristics of this particular

transducer for a PTC transducer is what

we see on the figure on the right hand

side. So you can very clearly see

that as the temperature increases the

resistance also increases.

There is interesting thing which we are

observing in this particular uh in this particular

particular

in this particular characteristics. You

see the relationship between the

resistance and temperature it is not

actually linear. It is nonlinear.

It is nonlinear. Now this poses a

problem. So we were talking about uh in

the previous discussions of current

sensors if at all the relation between

the input parameter and the output

parameter or the x-axis parameter and

y-axis parameter if it is linear it is

easy for us to characterize this

relationship. So in this case it is

difficult for us to characterize the

relationship. So we don't really have an

equation of uh known equation of any

sort in order to characterize these

kinds of things. So there are a couple

of things we can do to uh tackle this

particular issue. We can try to uh go

for curve fitting techniques and then we

can generate a equation using these

curve fitting techniques. So we end up

getting an equation something like this.

It might be a transcendental equation

also. We don't know how it comes out. It

might be anything. Finally it should be

something like y is a function of x

something like that. So what or how this

x is related to y that is what we have

to find out. So curve fitting technique

is one thing which we can probably

employ to do this another easier method.

So this is mathematically computational

intensive uh task curve fitting

technique or using any other similar

kind of technique. So the very easier

method is to go for something called as

lookup table method. So what these

lookup table methods are what actually

lookup table means it is as simple as

this. It is a table of information where

the information is present which we look

into. So if simply you have a table

which lists

the different values of the output to

the input parameter. So you will have

just two columns or the x-axis parameter

and y-axis parameter.

So the relation between these two are

table. So you just take a PTCM

temperature sensor then you uh apply

some temperature to it. You will get

some resistance. This particular value

we map it. So value one this side I1 and

O1 on the other side. In a similar way

we try to get the different values of

outputs we'll be getting for different

temperature values and then we list

everything out. Now we store this

particular information inside our memory

microcontroller's memory so that the

microcontroller CPU can look into this

table. Your ADC says this is the

resistance or this is the voltage. Now

directly your CPU comes and checks this

table. Okay, for a value of Y or for a

value of 01 the temperature is this

much. It comes to know in that way. So

this kind of method is very simple. only

thing a simple experimentation one-time

experimentation is required to be

conducted in order to have these kinds

of informations collected. So once these

informations are collected and tableated

we can use a lookup table method or the

microcontroller can use this lookup

table method to assess the uh resistance

or to assess the temperature from the

output parameter voltage or resistance.

So that is the idea behind lookup table

method. So this kind of method is widely

used very often used I shouldn't say

widely very often used for uh uh uh

while developing embedded control programs.

programs.

Okay. Now we will focus upon the the

sensor what you are seeing right here.

So now whatever you see here we call

this as a transducer. There is a minor

you know that there is a minor

difference between the words sensor and

transducers. Both of them they are used

to get idea about the physical parameter

but when it comes to a sensor it is just

responding to a physical stimuli. On the

other hand these transducers are

supposed to convert the signals from one

form to another. For instance, here the

input parameter is going to be temperature

temperature

which is a non-elect electrical quantity

and the output of this this particular

thing which we are going to call it as a

transducer. It is going to be in

electrical nature. You are going to get

a electrical voltage. Now it is

converting from one form to another. So

this kind of thing usually is referred

as a transducer. Most often you'll be

seeing these kinds of transducers coming

as uh uh element for measuring the

physical parameters. So such a kind of

transducer is what you have. So this is

a passive transducer passive sensor

which means that you need to energize

this particular sensing element. So you

internally have the thermister element

something like a resistor. So if you

want to know then you have to apply a

voltage depending upon the resistance.

the resistance may increase or decrease

depending upon this particular

resistance. The amount of current

flowing through will be different. So

let me draw the diagram once again here.

here.

Assume you have applied a fixed voltage

some fixed voltage whatever you decide

based upon the ADC which you are using.

So this fixed voltage this is going to

be constant. Let us assume it is 5

volts. It is a 5 volt constant voltage.

It is applied here. Now if at all the

resistance is fixed something like 1 ohm

the current flowing through also will be

fixed. Whereas if the resistance is

varying the current flowing through it

also will be varying. This is exactly

what we are talking about. These

thermisters have the property that the

resistance will vary increase or

decrease depending upon the temperature

vari variations. If it is a PTSC

thermister then as a temperature

increases the resistance also will

increase. If it is NTC the relation will

be inversely proportional. Now in order

to get the electrical signal you need to

energize these transducers first and

that is what you exactly seen here. Now

after you have energized these

transducers the output wtage will be

available. The output wtage

corresponding to the input parameter

will be available. If this voltage is

very small for your ADC terminals just

like in the previous discussions if you

have just say in the range of 0 to 0.5

volt produced by this transducer you

have to amplify it and that is when you

start using amplifier circuit like this

okay that is about the transducers I

mean thermisters.

So here once again let us recolct the

usage of lookup tables is one thing

which we have to be very clear about

that uh please keep in mind.

So this is usually used to tackle the

situations where the sensor

characteristics is nonlinear. So only

when the sensor characteristics is

nonlinear then you will be going for

characterizing these things in the form

of by using lookup tables.

The next category is uh the resistance

temperature detections detectors. So

once again this RTD's working principle

is in a manner similar to that of our

thermisters. The resistance changes vary

uh the temperature the resistance

changes measure the temperature

variation you'll be able to get idea

about the input temperature variations.

Now if you look at the diagram on the

right hand side you have

different kinds of circuit uh

uh wirings configurations. You have

something called as two wire

connections, four wire connections. Uh

these kinds of things are often used

when we are bothered about the accuracy

as such. Sometimes when we are uh

talking about the voltage low voltage

drops created by these sensing elements.

If the voltage drop created by these

sensing elements are very small then the

lead resistance also comes into picture

and it corrupts the actual data which we

are trying to measure. Once again let me

repeat the wires. The wires are nothing

but conductors isn't it? So we know that

the resistance of a conductor

practically theoretically these

conductors are not supposed to have any

resistance. Practically these things are

supposed to have some finite amount of

resistance. So this resistance is

dependent upon certain physical aspects.

You have studied about this relation

some time back long back in your PU just

recollected. So the resistivity, the

length and the area the physical aspects

of this particular conductor plays a

role in determining the resistive

resistance of a conductor. Now naturally

when the resistance is finite even if it

is 0.1 or 2 even if it is something like

this the current flowing through this

obviously is going to create some voltage. Now this drop when it is

voltage. Now this drop when it is measured by the ADC remember this is the

measured by the ADC remember this is the voltage our ADC will be sensing. Now

voltage our ADC will be sensing. Now when this conductor also is introducing

when this conductor also is introducing some amount of lead resistance the

some amount of lead resistance the conductor resistance then we don't get

conductor resistance then we don't get to read the actual temperature actual

to read the actual temperature actual variation of these RTDs or any other

variation of these RTDs or any other similar sensor elements. So now our

similar sensor elements. So now our input readings are the data is getting

input readings are the data is getting in a way uh uh it's not corrupted

in a way uh uh it's not corrupted actually it gets uh modified we don't

actually it gets uh modified we don't get to measure the actual temperature

get to measure the actual temperature actual readings we won't be able to get

actual readings we won't be able to get it. So that is when we tend to go for uh

it. So that is when we tend to go for uh methods which overcomes these things. So

methods which overcomes these things. So we use four-wire methods or three-wire

we use four-wire methods or three-wire methods to assess what will be the lead

methods to assess what will be the lead resistance and then we subtract it from

resistance and then we subtract it from this we can do it prior to starting at

this we can do it prior to starting at the measurement phase. Once we have got

the measurement phase. Once we have got idea that this is the uh resistance of

idea that this is the uh resistance of these leads assume that this is say.1

these leads assume that this is say.1 ohm on this side and 1 ohm on this side.

ohm on this side and 1 ohm on this side. So while we are making calculations we

So while we are making calculations we can subtract whatever resistance which

can subtract whatever resistance which we are getting for this

we are getting for this pardon this value we can subtract 2 ohms

pardon this value we can subtract 2 ohms and then we can use the resulting value

and then we can use the resulting value to get sense of the actual temperature.

to get sense of the actual temperature. This way we are able to overcome the

This way we are able to overcome the disadvantages of uh uh the voltage drops

disadvantages of uh uh the voltage drops created by these leads.

created by these leads. So only when we are talking about uh

So only when we are talking about uh designing then we are supposed to look

designing then we are supposed to look into it. So if you are simply looking at

into it. So if you are simply looking at writing abroad programs we just get

writing abroad programs we just get informations about these things either

informations about these things either from the design team or perhaps from the

from the design team or perhaps from the data sheet also usually manufacturers

data sheet also usually manufacturers data sheet they will supply every single

data sheet they will supply every single thing like this and they will give

thing like this and they will give application note also how you can tackle

application note also how you can tackle these issues. As I told you earlier data

these issues. As I told you earlier data sheets are the best friends for a design

sheets are the best friends for a design engineer. not only design engineer for

engineer. not only design engineer for the embedded engineer also. So he has to

the embedded engineer also. So he has to know everything if he wants to write a

know everything if he wants to write a reliable program a program which

reliable program a program which responds reliably.

responds reliably. So the next type of sensor which we will

So the next type of sensor which we will be talking about is the IC based

be talking about is the IC based sensors. This is most often preferred in

sensors. This is most often preferred in uh environment where you want to read

uh environment where you want to read the data not as an analog value but as a

the data not as an analog value but as a digital value.

digital value. I am repeating it once again. Until now

I am repeating it once again. Until now when we are talking about thermisters

when we are talking about thermisters and RTDs, we are trying to generate a

and RTDs, we are trying to generate a voltage and then we are trying to read

voltage and then we are trying to read this. This is an analog quantity which

this. This is an analog quantity which I'm talking about. Sometimes we might be

I'm talking about. Sometimes we might be interested in converting this analog

interested in converting this analog value and reading it as a digital data.

value and reading it as a digital data. So in those instances we tend to go for

So in those instances we tend to go for IC based solutions. We do have IC based

IC based solutions. We do have IC based solutions which give us analog readings

solutions which give us analog readings also something like this. So this LM35

also something like this. So this LM35 is a very popular one among habies even

is a very popular one among habies even to a certain extent it is used in some

to a certain extent it is used in some industrial applications too but not

industrial applications too but not majorly where uh things are not that

majorly where uh things are not that critical. You might see these LM32 based

critical. You might see these LM32 based things. So here you will be ending up

things. So here you will be ending up getting a voltage analog voltage

getting a voltage analog voltage corresponding to the temperature. So

corresponding to the temperature. So this particular uh body it will be

this particular uh body it will be sensing the temperature correspondingly

sensing the temperature correspondingly it will be varying the output voltage.

it will be varying the output voltage. This is your analog sensor. So when you

This is your analog sensor. So when you want this data to be passed on to your

want this data to be passed on to your microcontroller

microcontroller your emboded controller as a digital

your emboded controller as a digital information that is when you go for uh

information that is when you go for uh second kind of IC based solutions. So

second kind of IC based solutions. So here these kinds of IC's measures the

here these kinds of IC's measures the temperature. It internally converts

temperature. It internally converts them into analog values

them into analog values and then it converts it into digital.

and then it converts it into digital. When I say digital you shouldn't imagine

When I say digital you shouldn't imagine simply as zeros and ones. You will have

simply as zeros and ones. You will have sets of zeros and ones. For instance we

sets of zeros and ones. For instance we will take four bits. We have B4, B3, B2

will take four bits. We have B4, B3, B2 and B1. I didn't start from B not just

and B1. I didn't start from B not just for understanding. I have written it

for understanding. I have written it from B4 to B3. Assume this analog data

from B4 to B3. Assume this analog data is converted to four bits. These four

is converted to four bits. These four bits they are not going to be

bits they are not going to be communicated to the microcontroller as a

communicated to the microcontroller as a parallel data. These four bits are not

parallel data. These four bits are not going to go parallelly. They are going

going to go parallelly. They are going to go serially one after another.

to go serially one after another. So this kind of serial protocol is being

So this kind of serial protocol is being used by these IC's internal mechanisms

used by these IC's internal mechanisms in order to transfer this data serially

in order to transfer this data serially to your microcontroller. which means

to your microcontroller. which means that just one wire or two wires are more

that just one wire or two wires are more than sufficient to transmit even a 12

than sufficient to transmit even a 12 bit data. We won't require that many

bit data. We won't require that many wires.

wires. So these kinds of communications usually

So these kinds of communications usually happen in the form of I2C

happen in the form of I2C packets. So inter integrated circuit bus

packets. So inter integrated circuit bus protocol

protocol will be used for communicating

will be used for communicating informations like this to the

informations like this to the microcontroller units or any other

microcontroller units or any other integrated circuits present inside your

integrated circuits present inside your boards. So this is uh done for various

boards. So this is uh done for various uh reasons including reducing the number

uh reasons including reducing the number of wires or for the sake of uh reducing

of wires or for the sake of uh reducing the length of conductors used. Lots of

the length of conductors used. Lots of uh reasons are there. Of course, it has

uh reasons are there. Of course, it has its limitation that the data transfer

its limitation that the data transfer rate will be limited. It is not parall

rate will be limited. It is not parall transfer. It is serial transfer. But we

transfer. It is serial transfer. But we can live with it. We don't see a

can live with it. We don't see a temperature rise within 1 microcond or

temperature rise within 1 microcond or even 1 millisecond, not even 1 second.

even 1 millisecond, not even 1 second. The temperature rise might be measured.

The temperature rise might be measured. There will be a significant measurable

There will be a significant measurable temperature difference maybe in the

temperature difference maybe in the order of around 10 seconds or maybe 1

order of around 10 seconds or maybe 1 minute or sometimes 10 minutes. it will

minute or sometimes 10 minutes. it will be very slowly varying which means that

be very slowly varying which means that we can live with the slow transmission

we can live with the slow transmission rate slow uh rate of uh transmission of

rate slow uh rate of uh transmission of these temperature information. So

these temperature information. So whenever we need IC based solutions we

whenever we need IC based solutions we can go for these kinds of things. So

can go for these kinds of things. So these are the three widely used sensors

these are the three widely used sensors and of course we have the last variety

and of course we have the last variety which I have listed which is kind of

which I have listed which is kind of interesting and personal my personal

interesting and personal my personal favorite also the infrared temperature

favorite also the infrared temperature sensors. So then these are used when we

sensors. So then these are used when we cannot get into contact of the body or

cannot get into contact of the body or the place where you have to measure the

the place where you have to measure the temperature. So these are going to

temperature. So these are going to depend upon the infrared rays emitted by

depend upon the infrared rays emitted by the heart's heat sources and thereby

the heart's heat sources and thereby assessing what is the temperature on

assessing what is the temperature on that particular location or on that

that particular location or on that particular body. So naturally these

particular body. So naturally these kinds of sensors are the costliest of

kinds of sensors are the costliest of all sensors and uh it doesn't justify to

all sensors and uh it doesn't justify to be used in regular automotive

be used in regular automotive applications. So hardly very rarely

applications. So hardly very rarely you'll be seeing these kinds of things.

you'll be seeing these kinds of things. So most often we end up seeing these

So most often we end up seeing these kinds of temperature sensors as a array

kinds of temperature sensors as a array of sensors. You will be seeing something

of sensors. You will be seeing something like array. You won't see a single

like array. You won't see a single infrared LED there. You'll I mean

infrared LED there. You'll I mean transistor there. you will be having

transistor there. you will be having array of sensors something like this.

array of sensors something like this. For instance, this particular uh uh

For instance, this particular uh uh sensor Panasonic's AMG series sensor, it

sensor Panasonic's AMG series sensor, it has 16

has 16 infrared diodes arranged in rows and

infrared diodes arranged in rows and columns. Sorry, not 16, it is eight

columns. Sorry, not 16, it is eight sensors on column and rows. So total of

sensors on column and rows. So total of you have around 64

you have around 64 not 64 I shouldn't try is 64 different

not 64 I shouldn't try is 64 different sensors. So you have a total of 64

sensors. So you have a total of 64 sensors arranged in the form of array.

sensors arranged in the form of array. So naturally you can assume whatever

So naturally you can assume whatever information youropile

information youropile these are called as thermopiles they are

these are called as thermopiles they are giving it will be in the form of a

giving it will be in the form of a photograph something like a photograph

photograph something like a photograph it will be giving an information about a

it will be giving an information about a wide area. So these kinds of photographs

wide area. So these kinds of photographs are called as thermographs which means

are called as thermographs which means that we will get to know about the

that we will get to know about the temperature profile

temperature profile of

of these are thermograph these kinds of

these are thermograph these kinds of thermographs like the picture what you

thermographs like the picture what you see here it will be giving information

see here it will be giving information about multiple objects. So that is one

about multiple objects. So that is one advantage but these kinds of advantages

advantage but these kinds of advantages are not required in EV applications. So

are not required in EV applications. So we will be going for contact type

we will be going for contact type temperature sensors one. So if at all

temperature sensors one. So if at all these things kindle your interest you

these things kindle your interest you can also always think about uh these

can also always think about uh these things collect more informations and

things collect more informations and maybe you can learn more about this and

maybe you can learn more about this and interestingly if you see all these data

interestingly if you see all these data which are measured by this temperature

which are measured by this temperature sensor they are communicated by using

sensor they are communicated by using I2C protocol. You see these terminals

I2C protocol. You see these terminals somewhere here you'll be seeing the

somewhere here you'll be seeing the serial data and serial clock terminals.

serial data and serial clock terminals. So these are communicating its data

So these are communicating its data using serial protocol. So most of the IC

using serial protocol. So most of the IC based solutions temperature sensing IC

based solutions temperature sensing IC based solutions they'll be transmitting

based solutions they'll be transmitting information digitally by using I2C

information digitally by using I2C protocol. So what I2C protocol are or

protocol. So what I2C protocol are or what can or these kinds of protocols are

what can or these kinds of protocols are that is always a thing which you have to

that is always a thing which you have to be aware of.

be aware of. Bus protocols are important to be known

Bus protocols are important to be known by any embedded systems engineer

by any embedded systems engineer especially automative embedded systems

especially automative embedded systems engineer should be aware of some of

engineer should be aware of some of these at least like this lin protocol

these at least like this lin protocol can I2C especially these things you have

can I2C especially these things you have to be aware of.

to be aware of. So with that note about the primary

So with that note about the primary sensors, we will just uh go to yes

sensors, we will just uh go to yes we will just try to figure out uh which

we will just try to figure out uh which application

application deserves the use of which sensors. We

deserves the use of which sensors. We will try to make a judicious choice. So

will try to make a judicious choice. So just like in the previous sessions we

just like in the previous sessions we have listed the different places or the

have listed the different places or the different subsystems where we have to

different subsystems where we have to measure the temperature from uh starting

measure the temperature from uh starting from battery pack to onboard chargers.

from battery pack to onboard chargers. So let us try to figure out the

So let us try to figure out the available choices. Uh it is listed at

available choices. Uh it is listed at the bottom of the uh screen. Just try

the bottom of the uh screen. Just try let us try to make a

let us try to make a decision what kind of temperature will

decision what kind of temperature will we prefer for a battery pack temperature

we prefer for a battery pack temperature sensing. Remember it is battery pack. We

sensing. Remember it is battery pack. We are not talking about cells. We can

are not talking about cells. We can include cells also whether it is cells

include cells also whether it is cells or battery pack. What kind of

or battery pack. What kind of temperature sensor you possibly will

temperature sensor you possibly will think of? You can put your uh thoughts

think of? You can put your uh thoughts in the comments.

So battery pack temperature sensing one of the

of the contact type temperature sensors are

contact type temperature sensors are supposed to be employed. So your choice

supposed to be employed. So your choice can either be a thermister or an RTD.

can either be a thermister or an RTD. Both of them are okay for that. Traction

Both of them are okay for that. Traction motors once again you go for thermisters

motors once again you go for thermisters or RTDs. You can even think about IC

or RTDs. You can even think about IC based temperature sensors. Battery packs

based temperature sensors. Battery packs IC based temperature is also used

IC based temperature is also used especially when it comes as a part of

especially when it comes as a part of the BMS.

the BMS. It comes when it comes as a part of the

It comes when it comes as a part of the BMS. It is much more advantageous.

BMS. It is much more advantageous. Inverters, onboard charges, every other

Inverters, onboard charges, every other things you can use thermisters or RTDs.

things you can use thermisters or RTDs. In fact, thermisters are the one which

In fact, thermisters are the one which are very commonly

are very commonly observed as a temperature sensor used in

observed as a temperature sensor used in automotive applications.

automotive applications. Even for measuring cabin temperature,

Even for measuring cabin temperature, you can select one of these things. Once

you can select one of these things. Once again, thermisters.

You see that? Yes. Now we have uh this information presented there.

You can just glance through the informations here.

informations here. Now the selection of these kinds of

Now the selection of these kinds of thermisters

thermisters as discussed in the previous sessions

as discussed in the previous sessions depends upon multiple factors. One

depends upon multiple factors. One factor obviously is going to be the cost

factor obviously is going to be the cost factor. There is no doubt about that. So

factor. There is no doubt about that. So we look at the cost of these sensors and

we look at the cost of these sensors and then we decide which sensor we are

then we decide which sensor we are supposed to use. The other parameters

supposed to use. The other parameters which we are looking supposed to look

which we are looking supposed to look into is starting from the stability, the

into is starting from the stability, the reliability, accuracy, all these things.

reliability, accuracy, all these things. Now when we are making a decision about

Now when we are making a decision about the selection you have to keep in mind

the selection you have to keep in mind always the safety standards the ISO

always the safety standards the ISO standards we have been talking about for

standards we have been talking about for the past two days and these things we

the past two days and these things we have to make sure they are uh confirming

have to make sure they are uh confirming to the safety levels what we were seeing

to the safety levels what we were seeing yesterday as safety levels the five

yesterday as safety levels the five safety levels if it is a very critical

safety levels if it is a very critical uh level up to the level of D then we

uh level up to the level of D then we have to select it very carefully if it

have to select it very carefully if it is level A or no levels then we can go

is level A or no levels then we can go for

So we end up saying that thermisters are from this we are going to give a final

from this we are going to give a final conclusion that thermisters of the

conclusion that thermisters of the widely employed

widely employed NTC thermostat especially negative

NTC thermostat especially negative temperature coefficient thermisters

temperature coefficient thermisters especially they are widely used in these

especially they are widely used in these applications automotive applications and

applications automotive applications and sometimes you might end up seeing the

sometimes you might end up seeing the RTDs also where accuracy is higher. Now

RTDs also where accuracy is higher. Now I have listed uh some of the

I have listed uh some of the characteristics or some of the

characteristics or some of the parameters which you will use to compare

parameters which you will use to compare and take a informed decision about which

and take a informed decision about which sensor to use. So you can take a couple

sensor to use. So you can take a couple of minutes to go through the information

of minutes to go through the information on this particular slide. You have

on this particular slide. You have thermisters listed there RTD PT00 is one

thermisters listed there RTD PT00 is one of the famous sensors used in

of the famous sensors used in industries. Industrial grade PT sensors

industries. Industrial grade PT sensors you may widely see in every temperature

you may widely see in every temperature sensor applications that also has been

sensor applications that also has been listed in addition to the IC based

listed in addition to the IC based sensor solutions also. Now when you

sensor solutions also. Now when you evaluate these parameters you will come

evaluate these parameters you will come to a conclusion that in a way NTCS and

to a conclusion that in a way NTCS and RTCS are the preferred solutions. You

RTCS are the preferred solutions. You can go for other solutions also but

can go for other solutions also but these things are comparatively cheap to

these things are comparatively cheap to the other things and it does have little

the other things and it does have little bit of uh good sensitivity. Sensitivity

bit of uh good sensitivity. Sensitivity is one of the important parameter which

is one of the important parameter which we have to keep in mind and in long run

we have to keep in mind and in long run the stability also matters. Right now

the stability also matters. Right now when you purchase the sensor it might

when you purchase the sensor it might give a good reading and based upon that

give a good reading and based upon that characteristics we would have written a

characteristics we would have written a program and if this response

program and if this response characteristics is not remaining stable.

characteristics is not remaining stable. If there is any kind of time degradation

If there is any kind of time degradation like the drift parameter mentioned there

like the drift parameter mentioned there if you have that and after one month or

if you have that and after one month or one year or two year the sensor

one year or two year the sensor parameter changes then it'll be required

parameter changes then it'll be required for us to change the algorithm. So if it

for us to change the algorithm. So if it is not done then we will be putting our

is not done then we will be putting our automotive things to jeopardy. It will

automotive things to jeopardy. It will be a kind of safety critical thing.

Now we will have a look into the kind of circuit arrangements which you will

circuit arrangements which you will possibly see while you are going for

possibly see while you are going for thermal management. So I'll project you

thermal management. So I'll project you the circuit.

So we have in this particular case a diagram which shows how temperature

diagram which shows how temperature measurements are done for measuring the

measurements are done for measuring the pack temperature information.

pack temperature information. So we mount a thermister on the back and

So we mount a thermister on the back and this particular information is used to

this particular information is used to feed to the ADC the temperature value

feed to the ADC the temperature value remember it is getting converted into

remember it is getting converted into voltage and that voltage is read by the

voltage and that voltage is read by the ADC and we have seen that these

ADC and we have seen that these thermisters PTC or NTC they have

thermisters PTC or NTC they have nonlinear relationship. So we are going

nonlinear relationship. So we are going for lookup table method and using this

for lookup table method and using this lookup table method we get to understand

lookup table method we get to understand what the temperature is. So this is how

what the temperature is. So this is how the uh implementation algorithm for the

the uh implementation algorithm for the important programs should look like. So

important programs should look like. So you have a table stored in the program

you have a table stored in the program memory. So this uh program memory

memory. So this uh program memory information the table lookup table

information the table lookup table information that can be used the ADC

information that can be used the ADC value ADC value that is the voltage

value ADC value that is the voltage value is taken and the table values are

value is taken and the table values are picked up whichever value matches on the

picked up whichever value matches on the first column that information is picked

first column that information is picked up and then your algorithm decides that

up and then your algorithm decides that the current temperature is this much

the current temperature is this much maybe in the next session I'll try to

maybe in the next session I'll try to bring a kind of demonstrative algorithm

bring a kind of demonstrative algorithm that will give you much more clarity on

that will give you much more clarity on how the programs are written. for these

how the programs are written. for these uh situations.

So that's uh for this much is sufficient for us to know about how to measure

for us to know about how to measure temperatures and how to use this

temperatures and how to use this information further to take uh control

information further to take uh control decisions whether it is for protection

decisions whether it is for protection or any other things even if it is for

or any other things even if it is for cabin temperature maintain maintain

cabin temperature maintain maintain maintaining we can use a similar kind of

maintaining we can use a similar kind of algorithm. So if you have any doubt

algorithm. So if you have any doubt please post it in the chat box.

Yeah it looks like we have a couple of queries uh on voltage value how you will

queries uh on voltage value how you will get the temperature value exactly. Now

get the temperature value exactly. Now this is uh just the procedure is very

this is uh just the procedure is very similar to the procedure we have

similar to the procedure we have followed in the current sensor. In the

followed in the current sensor. In the beginning of the session, we have seen

beginning of the session, we have seen how to convert the uh the voltage

how to convert the uh the voltage readings of the ADC to know what current

readings of the ADC to know what current is flowing. In the same way, we have to

is flowing. In the same way, we have to characterize the relation between the

characterize the relation between the temperature and the voltage. Once we

temperature and the voltage. Once we have done that, once we have got a

have done that, once we have got a characteristic equation, we can use this

characteristic equation, we can use this to find out the temperature. That is how

to find out the temperature. That is how we know what the temperature is from the

we know what the temperature is from the ADC voltage. We have to characterize

ADC voltage. We have to characterize them. And most of the times if we look

them. And most of the times if we look into the data sheet for instance you

into the data sheet for instance you have looked into that LM35 isn't it?

have looked into that LM35 isn't it? Just simply download the data sheet

Just simply download the data sheet there will be a characteristic curve

there will be a characteristic curve represented there. This gives you this

represented there. This gives you this this gives you that required

this gives you that required information. So you can use this

information. So you can use this information for writing programs more

information for writing programs more than enough.

PPT once again at the end of the week I'll uh send it to uh as team from there

I'll uh send it to uh as team from there they will circulate it.

Okay. I'll stay online for another uh 5 minutes

minutes then we can

then we can end the session for today.

So try to uh do that tinkercad exercise today. If you have any doubts, we can

today. If you have any doubts, we can take it up in the forthcoming sessions.

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YouTube Transcript:Embedded Systems and Design & Development - Feb 18, 2026 | Afternoon | VisionAstraa EV Academy