Applications

What is a machine ? 3 idiots definition breakdown

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What is a machine - definition breakdown

Author – Saurabh Salvi

One of my favourite scene from ‘3 idiots’ movie is when Rancho is asked the definition of ‘Machine’ by his Professor. And we all know what he answers and we all love that explanation but professor didn’t seem to like that simplified version of his. Instead, he was much impressed by the definition given by Chatur and most of us (actually, all of us) just skipped that definition part.

What is a machine - 3 idiots movie scene (Rancho)
What is a machine - 3 idiots movie scene (Chatur)

Ofcourse, it’s not a great idea to mug up things without understanding (we have already discussed this point in Understanding Projectile Motion), but the definition of machine which he gives is also quite impressive. It goes something like this :

Definition :

“Machines are any combination of bodies so connected that their relative motions are constrained and by which means, force and motion may be transmitted and modified as a screw and its nut, or a lever arranged to turn about a fulcrum or a pulley about its pivot, etc. especially, a construction, more or less complex consisting of a combination of moving parts, or simple mechanical elements as wheels, levers, cams etc.”

In today’s blog, we will be breaking this definition down with the help of a very simple example which most of us (from PCM or PCB background) have studied i.e. Atwood machine – the simplest pulley-block system

Let’s divide the definition in parts and try to get this thing sorted out quickly :

1st part – “Machines are any combination of bodies so connected that their relative motions are constrained“

Look at body 1 and 2. Both the masses are so connected that their motions are dependent on one another. That’s what we call as – ‘the relative motion is constrained’

We can write the constraint relation for displacement between the two masses for this case as :

*Refer to this article for a detailed discussion on writing constrained relations : Click Here

It shows that if 1 comes down by ‘x’ metre, then 2 has to move up by ‘x’ metre. It’s all constrained !

2nd part – “and by which means, force and motion may be transmitted“

The gravitational force on 1 (m1*g) is transmitted through the string to affect the motion of 2.

Also, if 1 and 2 are of same mass, they don’t have any acceleration but in case the masses are different the accelerations of 1 and 2 get modified

We write FBD (free body diagram) equation for each body as :

What is a machine ? - pulley

3rd part – “as a screw and its nut, or a lever arranged to turn about a fulcrum or a pulley about its pivot, etc.“

This part explains about various examples of simple machines (screw-nut, lever, pulley).

Here, in this examples, we have pulley as a simple machine component as a part of this whole system.

4th part – “especially, a construction, more or less complex consisting of a combination of moving parts, or simple mechanical elements as wheels, levers, cams etc.“

Compared to a simple machine like pulley, we can say that Atwood machine system arrangement would come under a complex combination which has many moving parts in it such as :

  • Masses
  • String
  • Pulley

This was a short and fun kind of post just to make sure that all of the 3 idiots movie lovers can now breakdown this definition the next time they watch the movie! My aim was to explain this thing in the simplest way possible.

Also, I would like to add that just memorizing blindly doesn’t make any sense but understanding the definition would really help us to make our grip on the concepts much more better. I would also be quite impressed if Chatur had the understanding of this beautiful definition. But sadly, the character ‘Chatur’ doesn’t seem to be interested in all this 🙁

Keep Learning!

Physics & Electronics

How does a Multigrade Oil help in Car Engine ?

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We all have seen engine oil can somewhere, and most commonly at the mechanics shop. How you ever wondered about what’s this 5W-30 written on it ? Well, that’s what we are going to find out through this article

Topics Covered :

  • Short Introduction to viscosity
  • Temperature effect on viscosity
  • Need for Multigrade Oil

1. Short Introduction to viscosity

Let’s say you have water flowing over a flat plate. For sure, it’s not going to move freely. But, why do we say that ? The answer to this is : Viscosity. In simpler words, there is a kind of internal friction among the moving layers of the fluid. This resistance doesn’t let the fluid flow freely over the plate.

You can say that : ‘Friction loves keeping all the layers together’. In technical terms, we say : “Friction opposes relative motion”. Having this understanding, consider layer number 2. 

  • Layer 3 moves at a faster speed (v+dv) than 2. Hence, viscous force on lower layer of 3 acts in such a way that it gets slowed down. 
  • Layer 1 moves at slower speed (v-dv) than 2. Hence, viscous force on upper layer of 1 acts in such a way that it gets faster.

This fluid property of trying to keep and move the fluid ‘together’ is known as Viscosity.

The thing which separates the low viscous fluid from the highly viscous fluid is the amount of ‘strictness’ that the fluid shows for keeping them together.

Honey
Water
  • For example, water is less viscous than honey because water doesn’t care much about keeping the layers moving together. While, Honey is like a much ‘strict master’ who wants all of this layers to be united/together

Technical Definition for Viscosity –
The measure of resistance to relative motion within the fluid is called viscosity

2. Temperature effect on Viscosity

Effect of Temperature

Temperature does have an effect on viscosity of the fluid.

  • In case of a liquid, the molecules are bonded by a weak chemical bonds. 
  • On increasing temperature, you are actually providing enough thermal energy to the molecules that they break the bonds and become free. This causes the viscosity of fluid to decrease as there is no more dependency of fluid layers on one another because of moving apart. We say, the fluid becomes thinner.
  • While, at much lower temperatures, the fluid tends to become thicker.

3. Need for Multigrade Oil

Engine Oil is mostly used in order to ensure that there is proper lubrication among the contact parts i.e. with engine oil, we ensure there is no wear and tear among the interacting parts. 

3.1 What happens if oil is too thin or too thick ?

  • If the oil you use is too thin, it will just flow out of the surfaces very quickly and hence won’t be of any help

  • If the oil is too thick, a lot of power would go into just moving the parts through your ‘thick’ oil

3.2 Effect of Temperature on motor oil ?

So, knowing this, we choose a motor oil with some given viscosity. Now, consider 2 cases :

  • Case 1 : I use this oil in peak summer days
  • Case 2 : I use this oil in peak winters

We have already discussed about the effect of temperature on the viscosity. An oil with given viscosity would becomes thinner in peak summer and thicker on peak winters.

SOLUTION :
To overcome this, earlier people used a 30-weight motor oil (already thicker) in summers, so that, it thins out and reach required value because of high temperature WHILE they used 5-weight motor oil (already thin) in winters, so that, it thickens to reach the required value in peak winters due to low temperature.

BUT Now, we have come up with something even better, known as ‘Multigrade Oil‘. 

The speciality of this oil being that it can maintain a constant value of viscosity over a wide range of temperatures. Hence, we no longer have to change our oil from season to season. 

  • The key feature of multigrade oils is their ability to remain fluid when cold and provide adequate viscosity at higher temperatures.

Rating :

5W-30 means 5 weight in winter and 30 weight in summer. Hence, viscous nature remains maintained. Now, you know the reason behind 5W-30. Similarly, we also have 10W-40 and many more…

More Articles to Read :



How to write Coefficient of Restitution expression ? – Part 1


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29 August 2024
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Writing expression of Coefficient of Restitution (COR) can be a bit confusing. Also COR is one of the important concepts when it comes to designing sports equipments like racquets and balls



What is Total Internal Reflection ? – Geometrical Optics


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24 August 2024
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Total Internal Reflection, shortly known as TIR is one of the useful phenomenon in Geometrical or Ray Optics which has applications in lot of areas. In this Article, we discuss this topic in detail



Problem 7 : Red or Blue ?


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14 August 2024
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Physics Problem 7 – It mixes up Physics and Electronics. But not only that, the physics part itself consists of multiple concepts



Charge Induction in Metals and Non-metals


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21 July 2024
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Charge Induction is a topic under Electrostatics. The article describes the process of how actually charges get induced onto the surface of conducting and non-conducting bodies

How to interface RGB Led with Arduino ? – Arduino Project 2

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(View on Desktop/Laptop for Best Experience)


Click the photo to watch the associated video about this Project

RGB, as we all know, stands for :

  • Red
  • Green
  • Blue

They are one of the primary colours which can mixed in different proportions to result in various colours.

Table of Contents :

  • Problem Statement of our Project
  • How does RGB Led work ? – with Analogy
  • Components Required
  • Pinouts & Circuit Diagram
  • Explanation & Code Link
  • Assignment (Imp**)

1. Problem Statement 

  • We need to create a message for our loved ones but NOT as an direct text message. When I say loved one, it can be your mother, father, sister or just anyone whom you love and want to express your feelings ! 
  • This has to be done with the RGB LED, Arduino, etc. Frame your own way of conveying your message to the person with the help of components discussed

*Hint for the Solution : For this project, we will be showing ‘143’ with the help of RGB LED

2. How does RGB LED work ?

  • As we know, that Red, Green and Blue are one of the primary colours that can be used to obtain different colours.
  • This is done using different compositions or ratios of the 3 colours during mixing.
  • And how does mixing happen ? The answer is that – It just happens under one LED –> This makes the colours to get mixed

The best analogy is the painting palette which we normally use in our drawing classes. Consider having the smaller version of the paints. So how you used to obtain different colours ? –> By mixing those available colours in different ratios !

Just 6 colours poster paints
Drawing Palette
  • The given below are some of the shades which you can make with the help of RGB combinations : 
Photo Credits : https://en.wiktionary.org/

Also different shades of the colours can be obtained by varying the intensity of RGB colours

3. Components Required

  • Arduino Uno
  • RGB LED x1
  • Resistors (220 ohms) x3
  • Jumper Wires

4. Pinouts & Circuit Diagram

The RGB LED has 4 pins –

  • RED
  • BLUE
  • GREEN
  • GND

Always check the pin name associated with the pin. The pin order might change from manufacturer to manufacturer !

Important :

Treat each of the colour pin as a separate LED. Since only then you can control each colour on the LED individually.

  • This implies that you will need a separate resistor to protect each of the 3 LEDs – Therefore, we choose three, 220 ohms resistors
Schematic Diagram on TinkerCad :

Pin Connections :

5. Explanation & Code

So, as discussed in our Problem Statement, we are going to code our LED such that it somehow conveys the message ‘143’ (A modern way to say ” I love You “). This is how it can be done :

                                                                                                              Table for Code

  • If you look into the Pinouts Section above, you will notice that the Pins 5, 6 and 9 have a ‘~’ type of symbol adjacent to them on Arduino Board. This symbol represents that the Pin is a PWM pin.
  • PWM stands for Pulse Width Modulation
  • It’s a kind of additional Superpower which a digital pin is given in order to process the data in a different way if needed. We will be discussing about this in detail in upcoming Articles. 
  • For now Let’s take a small example and have an idea about PWM in Layman’s terms.

We know that Digital Pins have only 2 signals – ‘1’ and ‘0’ –> i.e. It’s either ON or it’s OFF respectively. This case is like a switch which we use to turn ON and turn OFF the fan. 


                                                                                   Fig. For Digital Pins without PWM

BUT Now, PWM is like adding a Regulator besides the switch (it’s just an addition to what we had before). This will allow us to vary and control the speed of the fan as well



                                                                                   Fig. For Digital Pins with PWM

Code :

The code to the Main Project Can be Found in the below attached GitHub File. The comments will guide you to understand the reasoning for that particular section of code.

GitHub Folder Link (Arduino Code for the Project) : Click Here

6. Assignment :

DOWNLOAD

assignment

Conclusion :

So, through this Mini Arduino Project-2, we learnt to interface RGB LED with Arduino and also learnt some basic working of the same. As discussed, we will be looking into PWM signals in a lot more detail in upcoming articles.

  • Don’t forget to attempt the Assignment Problem. It will allow you to apply the knowledge you gained in the article (Information + Arduino Code) 

Keep Learning !

Arrow Indicator Circuit – Arduino Project

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(View on Desktop/Laptop for Best Experience)

This project mainly aims to cover a part of Basics regarding Arduino IDE and Interfacing of Arduino with other components. Let’s get straight into building this project !

Table of Content :
  • Description of the Project
  • Components Needed
  • Understanding & Procedure
  • Explanation of Code

1. Description of the Project

Problem Statement :

Our main objective for the project is to make a Arrow Keypad like thing in order to control the LEDs. The LEDs indicates the direction corresponding to the button which we pressed on the keypad

Fig.1 Arrow Keypad
Fig.2 What LED pattern should appear when button is pressed

2. Components Needed

  • Arduino Uno
  • Breadboard
  • 4 Red LEDs 
  • 4 Push Buttons
  • 4 Resistors  (220 ohms)
  • Jumper Wires

Reference Article Alert !!

How to check Resistance value of your resistor? – Refer this Article : Dealing with Resistors

3. Understanding & Procedure

– Understanding

Note that, there are no connections among the LEDs. 

  • Each LED is separately connected to Arduino
  • Similarly each push button is also connected separately to Arduino Board
  • But the connection between the two (LED and pushbuttons) is done through Arduino. That’s the job of a Microcontroller –> ‘To connect the things as instructed in code’
Fig. Each LED and each pushbutton connected separately

We will see how to connect each component with Arduino

3.1 Single LED Connections :
  • The adjacent circuit diagram shows the connections that are to be made to control LED with the help of Arduino
  • The diagram has been prepared with the help of TinkerCad (Simulation Software)

*Code for the Blinking of LED can be found in our GitHub Repository – Click Here

3.2 Single Push Button Connections :
  • The pushbutton serves as an INPUT for most of the times.
  • It gives a value of 0 or LOW when not pressed and gives a value of 1 or HIGH when pressed.
  • There is another way to connect a pushbutton i.e. by adding a Pull-up Resistor.  

*Code for the usage of Push Button is also added in our GitHub Repository – Click Here

3.3 LED + Push Button :
  • Now that, we have learnt to interface button and LED separately, it’s time to interface them with Arduino at once.
  • Check the code. The comments will guide you to understand the idea behind each line

*Code for the ‘controlling LED with Push Button’ is also added in the GitHub Repository – Click Here

– Procedure

After Being Comfortable with the above three mini-projects, the main project is very easy to do as we have do the same thing, but now, it has to be done multiple times.

Step-1 :

We need the LED matrix type setup to be in a square shape (diamond shape). So accordingly we arrange setting up the LEDs and corresponding resistors to protect those LEDs

Reference Article Alert :

How to choose correct Resistor for a specific coloured LED ? – Refer the Article : Dealing with Resistors

You will learn that –> It is safe to use a higher resistance resistor than the required value. So we go for 220 ohms.

Connect the LEDs as learnt in Section 3.1

Step-2 :

  • Attach the 4 Push Buttons to the breadboard in a keypad fashion. 
  • The connections of each button has to be done with Arduino as explained in Section 3.2

Overall Diagram in TinkerCad can be shown as :

The same thing in Reality looks something like :

4. Explanation of Code :

The Complete Code for this Project can be found in the GitHub Repository by name ‘Main Project Code’ – Click Here

  • We are using some kind of nomenclature here in order to properly keep a track of which LED we are talking about or else which button we are referring to.


Below is the attached file for Code Explanation. This will exactly give you an idea of the flow that the project code has in it.

Code Explanation - Main Arduino Project

Actual Execution :

When fwd key is pressed :

When left key is pressed :

When right key is pressed :

When back key is pressed :

Conclusion :

So, with this, we have learnt to do the basic interfacing of the components with Arduino. There’s a still lot to learn about Arduino. There are also many sensors that can be used in order for different projects. 

This Article was all about keeping it as basic as possible so that it is much interesting for people/students to read and see

Keep Learning !

ESC Calculation & Electronics Connections

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For Best Experience, View on Desktop/Laptop 

#RC Airplane Series-6

In this article, we are going to learn to do the ESC Calculations. Also, we are going to study about the control systems connections (basically, how are the electronics are connected to each other) !!

Topics Covered :
  • What is ESC ?
  • How to choose a ESC ?
  • How to connect all the electronic components?
  • Use of Y-junction (optional)

1. What is ESC ?

ESC stands for Electronic Speed Controller. It’s job is to provide set appropriate voltage across the BLDC motor according to the throttle given on the transmitter. 

  • For example, Suppose, I give 25% throttle, so, to get the speed corresponding to 25% throttle, what should be voltage applied across the motor –> this is the job of ESC ! (speed is controlled by controlling current)
  • The main thing to understand is that, we will be controlling the voltage across the motor with the help of ESC. We are already aware of the motor kV relation :

  • So according to the relation, Varying the voltage will vary the RPM of the motor, which will result in speed variation as well !!

From the example itself, we can understand that choosing a proper ESC is very much crucial so that everything is under control and also safe at the same time 

Wiring connections for ESC :

                                                                                              Fig. Wiring Connections of ESC

2. How to choose ESC ?

Let’s undertand the procedure using an example !

Suppose, we finally choose the motor for our model: 

A2212 10T 1400kV motor

Step-1 : Find out the maximum current which the current draws. If this value is not directly given, it can be calculated from the relation

                                                                                                          P = V x I 

(‘P’ is max. power of motor, ‘V’ is the nominal voltage of our battery used and ‘I’ is the max current from motor)

Step-2 : But we should choose an ESC such that this maximum current value should just be 75% of the actual ESC current which we will be buying. (Read it again !). We call this current as ‘Actual ESC Current’

This implies that we need an ESC which has a rating of 20.25 A. But in reality, there is no such ESC with this current rating being manufactured. So we need to go with an ESC which has a bigger value than 20.25

We can go with 30A ESC or an 40A ESC would also be perfect !!

3. Connections of all Electronics

Now, by this article 6 of RC Airplane Series, we already got to know about all the basic electronic requirements for an RC Airplane. Let’s list it down :

  • Motor and Propeller
  • LiPo Battery
  • ESC (Electronic Speed Controller)
  • Receiver (On board)
  • Transmitter (Not on board)
  • 4 Servos (1 for each ailerons, 1 for elevator, 1 for rudder) 

In this example, let’s say we are using a 6 channel transmitter and receiver

  • Usually in most of the cases, we have to attach the connectors to the 2 wires assigned for battery in ESC. For this, we can use XT60 connector which is very commonly used as well. They come in a set of a female and male connector. The female one is to be attached to the ESC while the male one is to be attached to the battery

For more clarity on above figure, you can also refer to the diagram below

4. Why Y-junction wire for ailerons ? (optional)

  • If you look into the connection diagram carefully, we can see that the servos attached to the 2 ailerons are connected to a Y-junction wire. This then goes onto connect to the receiver and it uses just one channel on the receiver for 2 servos !!

The reason behind us doing this thing can be learnt from the article – RC Airplane Series-2 : ‘Understanding Control Surfaces’

  • In the above article, mainly focus on the ailerons part in order to understand the reasoning behind Y-junction cable. In short, we can summarize it as : 

           In order to get a roll, making the ailerons deflect in opposite sense helps even more. For example, if we need to take right roll, then             on giving just one stimulus through transmitter, the right aileron will deflect upwards while at the same time, the left aileron also                 deflects downwards

One Advantage and One Disadvantage !

Advantage :

  • We can get a better roll due to 2 ailerons moving in opposite sense and everything is completed by using just 1 channel

Disadvantage :

  • We can’t make the ailerons to be used as flaps since they will always move in opposite sense. (i.e. flaperons is not possible)

Conclusion : 

  • So in this RC Airplane-6, we have learnt to do the ESC Calculations. Similar stuff is used while drone designing as well since it also includes BLDC motors whose speed needs to be controlled. 
  • Here, we have completed the basic designing of RC Airplane. Hope you enjoyed the Series and got to learn something new through this. But again reminding you, this was just the Basics !! 

RC Airplane Series (All previous Articles)

Any suggestions from your side are welcomed !!

Keep Learning !!

All the Best !!

How to choose LiPo battery ?

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(For Best Experience, View on Desktop/Laptop)

Author – Saurabh Salvi

#RC Airplane Series – 5

In this article, we are going to learn about the correct battery selection for our RC Airplane Project. This step is very crucial as the battery is going to be serving as the powerhouse for the entire set of electronic components on the plane. 

I will be covering some examples as well for your clarity. Let’s directly dive into the topic !

Why choose LiPo Battery?

Among so many batteries, when it comes to the electronic projects (especially RC aircrafts), we directly choose Lipo over others. 

LiPo stands for Lithium Polymer batteries. These are known for their ‘High Energy Density‘. 

By comparing the definitions, we can see that, if more mass is accumulated in lesser volume, we term that substance as highly dense substance. Similarly, if given energy can be stored in a lesser volume, we term the substance as the one having ‘high energy density’ !

Battery Specifications :

When it comes to LiPo batteries, we have 3 main parameters which we need to check in order to select the right LiPo for our project. Those are :

  • Number of cells (Voltage of the battery (in volts))
  • Capacity (in mAh)
  • ‘C’ rating/discharge rate

Voltage of LiPo battery :

A battery is a combination of cells. So basically to calculate the total voltage of the battery, we need to know the voltage of a single cell. 

Thumbrule :

  • The volatge of the cell in Lipo battery should not go below 3.3V and also should not cross 4V as in both cases it might damage the cell and hence the battery
  • So, we decide a term called ‘Nominal Voltage‘. This is basically an approx. average value of the max and min voltages. In case of LiPo, we take it as 3.7 V. For batteries, we always consider the nominal voltage

‘S’ represents the number of cells

Based on the S number, we calculate the total voltage of battery.

For example, the above battery is ‘3S’ which implies that it has 3 cells in it. Therefore,

Suppose, we select a model for our BLDC motor : DYS D2826-10 1400KV Outrunner Brushless Motor

Now, we need to correctly choose our motor based on the motor suggested specifications or check datasheet

from Robu.in

Now, selecting 2s LiPo or 3s LiPo depends on your model and requirements. The more voltage you apply, the more RPM you will get for the same given motor by the relation :

Capacity of Battery :

The Capacity of Battery gives you an idea of the time in which the battery will get drained off. The unit of Capacity for LiPo is ‘mAh’. It stands for milli-Amp hours.

We try to understand the same with an example. Suppose I have a battery of 4200 mAh. 

  • It implies that my battery will get drained off completely if I keep drawing 4.2 A from the battery continuously for 1hr.
  • Now, from the same battery, if I draw only 2.1 A (less than 4.2 A), then the battery will drain off after 2 hrs ; giving me more usage time. 
  • Pretty Obvious that if you draw lesser current, the battery will allow more usage time !!

For RC Airplanes, Capacity plays an important role for determining the flight time (time for which the plane will fly).

We will discuss about Flight time in coming section below

‘C’ Rating / Discharge Rate :

This thing is nothing but a simple multiplier. It is used to know the actual strength of our battery. This value helps us to calculate the maximum current (continuous and burst) which the battery can provide safely !! 

Formulation : 

Some times, we need some more current than the maximum continuous current value as well. So in that case, the burst continuous current comes into picture. It shows that the battery can provide some extra amount of current as well if required though only for a short interval of time.  

Usually, on batteries, only continuous discharge rate is given. For burst rate, we need to check the battery specifications on websites

For example, 

My battery has specifications 2200 mAh, 11.1V and  I want to decide the appropriate C rating to be chosen. I also know that the maximum current requirement for all my electronic components (majorly motor) is 20 A.

Solution :

So, I need a battery which must have the strength/ability to continuously providing 20A (though its not always needed). By the above formula,

We get,                                                                          20 = 2.2 * (C rating)     

                                                                                         C rating = 9.1 C

So now, anything more than 9.1 C (like 10C, 15C, etc) is absolutely fine BUT less than 9.1 C is NOT OK !!

Flight Time Calculations :

A very important concept and is crucial especially for competitions were time constraints are there. As discussed in Capacity sub-section above, this concept is a lot dependent on the Capacity of battery. 

Note the step-by-step procedure :

After completing all the steps, we get a flight time value. But once this flight time is completed for an RC plane, the battery will be completely drained off !! And WE DON’T WANT THIS !!

  • It is always advisable for LiPo batteries to keep atleast 25 % remaining (i.e. use only 75 % of the battery). So if only 75 % of the battery is to be used, then we will obviously get only 75 % of our calculated flight time. This will be our min. actual flight time. It can be more than this but not less, since we calculated this value based on the ‘Max.’ current from motor.

Detailed Example

The below document is a short example designed to get you more clarity on the theory part. Do go through the document once you go through the article completely. Keep both, this article and the example side-by-side and then learn and analyze how it’s done !!

DOWNLOAD EXAMPLE FILE RC Airplane Series-5 Example

RC Airplane Series – All Articles  (You are at Part – 5 !)

Conclusion

From this article, we got to learn about the procedure to select the correct LiPo battery for our project. In the next upcoming articles, we will cover the ESC calculations and also learn about the thrust test. Till then, Enjoy Learning !!

All the Best !!

Motor & Propeller Selection

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For Best Experience, View on Desktop/Laptop

#RC Airplane Series – 4

Now, we enter into the electronics side of the RC Airplane . In this article, we discuss about ‘How shall we exactly choose a motor for our RC Airplane ?’. This is one of the very crucial step because your electric motor and propeller combination in RC Airplane does the work similar to the fan engines in real RC aircrafts. This motor + propeller combination is responsible to provide the necessary ‘thrust’ required.

Topics Covered :
  • Electronic Components in RC Airplane
  • Deciding the type of flight
  • Choosing the motor – Motor Terminologies & Procedure 
  • Choosing the appropriate Propeller
  • Example for Better Understanding

Just to clarify !

I am sure, you will have a question that, if in last article I asked you to refer a plan from online sources, then why not copy their electronic components as well. 

There’s a problem in that !!

Many students/hobbyists aim to participate in various aeromodelling competitions. And when there’s a competition, there are some rules/constraints which we need to follow. Basically, this is where, it’s important to know how to exactly model the aircraft (design part + electronics part) OR else if there were no rules, there are so many resources about ‘How to make an rc airplane ?’. So , everyone would just copy them !!

And apart from this, the joy and the interest which u generate in the field of aeromodelling once you try to understand these concepts is unmatchable !!

1. Electronic Components for RC Airplane

  • Motor + Propeller combination
  • ESC (Electronic Speed Controller)
  • Battery
  • Servo motors
  • Receiver
  • Connectors

Here, we are just naming the electronics needed to drive an RC plane. We cover the motor and propeller selection in this post. In the upcoming articles, we start discussing each one in detail. We are going to keep everything to the point but discuss the important and necessary things in detail.

2. Deciding the Type of Flight

In order to select motor, We need to first decide the type of flying which we need from our plane. 

And based on that, we have a term called ‘Thrust-to-weight’ ratio. Also known as ‘TWR’ or ‘T/W’. Based on the type of flying we choose, we need to fix our TWR accordingly. To elaborate,


  • So, the first step for motor selection will be to be fix the TWR for your plane.

3. Choosing the motor

We need to follow a specific procedure in order to get therequired motor. Refer to the following flowchart for that :

Step – 1 :

In the previous article, we learnt to calculate the the ‘model weight’ (i.e. only the design part). Now, we need to first assume the electronic components and calculate the ready-to-fly weight. It means that the plane is fully ready (design + electronics) to fly and the weight of the plane at that point of time is called here as ‘ready-to-fly‘ weight. 

Assuming electronic components :

  • Most of the components (motors, ESC, battery, etc) have their weight within a fixed range. And note that, you DON’T have to be very specific and exact for this. We need an approximate weight of aircraft. 
  • Refer the product’s website and check the specification section to get the weight
  • This part will become more clear once you have the knowledge of all the components used in RC plane. I have attached a file below as an example to demonstrate the whole process

Note : If you are using landing gears for your plane instead of hand takeoff, you need to include that weight as well.

Step – 2 :

From previous section, we have fixed our TWR. Use this value to calculate the thrust. This will be the thrust required to achieve the required TWR for aircraft.

Step-3 :

It is advised to use BLDC (Brushless DC motors) due to : 

  •  High Efficiency

 

  • Longer Life span

 

  • Better speed control

 

  • Prevents over-heating

 

Q. What is RPM of motor ?

The number of revolutions (one complete circle) that the motor rotates in one minute of time is known as RRM of motor. RPM stands for Revolutions per minute. For e.g. 2500 RPM implies the motor rotates 2500 times in one minute. So basically, RPM is the unit of ‘angular velocity‘ 

Q. What is kV of motor ?

kV rating of a motor gives the idea of : At what RPM will the motor run when a certain voltage is applied. For e.g. If we have a motor of 1000kV and lets say the safe operating voltage range is 5V-12V. So if I am operating the motor at 5V, the motor will run at 5000 RPM , while, if I operate it at 12V, it will run at 12000 RPM. 

Based on this, we can formulate kV rating as :

How to choose kV of motor ?

Recall the type of flying which you chose. 

Now, once the motor kV is fixed, then go to the online electronic stores’ website and search for the motors of the calculated kV which are able to provide the required thrust. A thrust value greater than required is OK !

(Look through the specifications/description section of the product’s page for thrust value)

 

Step – 4 :

The propeller is another very important factor to consider since this fan like thing is the most responsible to generate the thrust required for our airplane. Check the datasheet or the recommended propeller size for the selected motor

4. Choosing Appropriate Propeller :

Working :

The propeller basically ‘pushes’ the air backwards so that the reaction force is acted on the propeller makes it move in forward direction. The working of propeller is a simple application of Newton’s third law.

Dimensions of Propeller

Diameter : The end to end length of the propeller. Mainly responsible for the rotary motion

Pitch : It is the distance covered by propeller in forward direction when one revolution is completed. Pitch is mostly responsible for the translatory motion of aircraft. Pitch is connected to the speed of the aircraft.

Notation : Example : 10×4.5 propeller implies diameter = 10 in & pitch = 4.5 in

How to select a Propeller ?

Again recall the type of flying chosen for your aircraft. Based on that, we need to fix the size of the propeller. 

Consider the below example (pdf file) for better understanding

5. Example :

A problem statement has been given (Like a competition) and based on the constraints, the procedure to select a motor has been given. Go through it thoroughly to get a complete understanding. (We are assuming that we chose some plan and on calculating the model weight of airplane, it came out to be 250 g.

DOWNLOAD

example for motor (1) (1)

Enjoy Learning !!

RC Airplane Series – All Articles  (You are at Part – 4 !)

Designing your Airplane !!

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#RC Airplane Series-3

In this article, we are going to discuss about designing the plane and after which in the next article (RC Airplane Series – 4), we discuss how shall we exactly select a motor for our RC Airplane. There is proper procedure for motor selection and is one of the important step in RC airplane designing. 

Designing the plane

This RC Airplane Series is going to be for ‘Beginners’ or for the ones who are not much experienced in this field but just want to know the basics of RC Airplane. Due to this reason, we avoid getting into the details of the analysis. The actual Analysis includes a lot more like: Aerofoil selection through XFLR software, ‘Ansys Fluent’ software for model analysis, etc. 

But for now, we keep it very simple  !!

For beginners, a suggestion would be to use online available plans in order to develop your aircrafts. By readymade plans, I mean that , you can get information with figures about the dimensions of fuselage, rudder, elevator, horizontal stabilizer, vertical stabilizer and all…..

Example (for application purpose)

Let’s take an example for now : 

I have considered this below shown plan as an example. You will get a lot of such similar plans online on various youtube channels and website. 

The one which I am using below is from the website :  https://www.rcpano.net/2020/01/28/fpv-airplane-making-rc-airplane/ . I have modified the plan a bit for simplicity ! And also this website does have a lot of more plans. Do check it out !!

DOWNLOAD

Design Plan example final
  • As shown in the above flowchart, after selecting a plan, we need to choose the material which we are going to use.

In this case, I decided to go with styrofoam and after which I searched for the density of styrofoam on the internet or you can also get it in the ‘specifications’ section from the website page using which you are going to buy it.

– The density came out to be 60 g/L.

  • Then, We calculate the mass of the seperate component using the density formula.
  •  For this, first calculate the Area first. Area can be calculated by breaking the figure into simple geometric figures (rectangles, triangles, trapezium, etc) . Then, calculate volume and then calculate mass using density formula.

Conclusion

This was a very short article on the designing of RC Airplane. We will for sure discuss this topic again at an Advanced Level. But for now, for the Beginners stage, lets keep it simple and easy to understand !! After all that’s our main goal.

Enjoy Learning !

RC Airplane Series – All Articles  (You are at Part – 3 !)

GPS Working

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In this specific article, we are going to learn about the working of GPS. In the upcoming articles, we will be dealing with the interfacing of of GPS module with the Arduino. I feel that it’s important to know the working of the module which we use in our project instead of just learning about ‘how to make the module throw it’s data values at us”…..

GPS stands for Global Positioning System and is mainly used to locate the exact location of the receiver with the help of data which it gives (out of which most important is Longitude and Latitude coordinates)

Working :

– The working of the GPS module is based on the communication between the satellites and the GPS receiver module.  For locating the position of a place on earth, we need several parameters like Longitude and Latitude (2-D) and an extra Altitude (for 3-D)

– To locate the position, in GPS, we have something known as Trilateration.

 In 2-D, 

 we need a total of 2 satellites (say S1 and S2 here). We    are suppose located at point O and we need our location through GPS.

                                                                                   Fig. Determination of position in 2-D

– This implies that, O is somewhere on the region common to circle-1 and circle-2. This means it lies in the points of intersection of circle      1  & 2 (here O and P).

– To decide between O and P, we take into account the circle-3 which is the earth surface itself. All the 3 circles intersect at O (therefore, P is eliminated) and hence we obtain the position of a GPS receiver in 2-D.

In 3-D,

– We need a total of 3 satellites for locating position of GPS receiver

Here, we need to consider just the spheres instead of circle. 

For quick overview,

But, there exists a problem of time delay, since the satellites have accurate atomic clocks while the GPS receivers uses the clocks which are installed in mobile phones.

But since all the satellites use the same specifications for atomic clock, the ‘time offset’ is the same. Even error of microseconds can give an error in kilometers !! Hence we use fourth satellite (S4).

As we discussed earlier, that we need the distance ‘d’ for locating the positions of satellites. 

  • But HOW DO WE EXACTLY DETERMINE ‘d’ ?

The ‘radio signal’ which is sent, it carries 2 information mainly :
          – Exact time when it was transmitted (t1)
          – Position of satellite

Now the receiver receives the signal at time t2 (say) :

The below is about What happens inside the GPS receiver (mainly a topic of discussion for our next Article)

Keep Learning !!

Understanding the Control Surfaces !

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# RC Airplane Series-2

In the previous part (RC Airplane Series -1) , We learnt about the wings of the aircraft and what is the reason behind the generation of Lift for the airplane. Now that we have learnt to take the airplane into the air, it’s time to control the aircraft. So, in this part, we are going to learn how are the control surfaces used in order to control the aircraft properly.

TOPICS TO BE COVERED :
  • What are different control surfaces in aircraft ?
  • Different dimensions of movement 
  • Aileron
  • Elevator
  • Rudder
  • Flaps

1. Different Control Surfaces

For the controls part, we have them divided into two parts : Primary and Secondary Control Surfaces

  • Primary : Ailerons, Rudder, Elevator

           (These are the necessary ones! Like Air, Water and Food for us)

  • Secondary : Flaps 

           (These are the extra ones which help in controlling the aircraft more precisely) In the Secondary part, we do have some more surfaces, but for basic RC planes, Flaps are enough 

                                                                          Fig. Positions of Ailerons, Rudder & Elevator


2. Dimensions of Movements :

There are basically 3 axes about which movement of the aircraft happens :

  • Longitudinal : It goes from nose to tail of the aircraft
  • Lateral : It goes from wingtip to wingtip and is perpendicular to the longitudinal axis
  • Vertical : It is mutually perpendicular to both, longitudinal and lateral axis

                                                                               Fig. Movements exhibited by an aircraft

  • Pitch : It is the rotational motion of the aircraft about the Lateral Axis (Nose – Up and Down)
  • Roll : Rotation about longitudinal axis is Roll. During this, the aircraft tilts its wing up and down
  • Yaw : Rotation about vertical axis is Yaw. Basically, moving right and left in the plane itself



                                                                                              Fig. How it exactly happens?

3. Ailerons :

– Ailerons are the control surfaces situated on the wings and are responsible for the ‘Roll’ motion of aircraft.

  • There are mainly 2 types of Ailerons (in Trainer Aircraft mostly) : Strip Aileron and Normal Ailerons

           Strip Ailerons are the ones which span over the entire half wing and have a width = 1/8 of chord length

           In normal ones, the length = 1/4 of wingspan and are situated towards wingtip and have a width = 1/4 of chord length

Working of Aileron :

For example, we need our airplane to roll towards right. For this to happen, the Right Wing should get lowered while the Left wing should be lifted up (when viewed from tail)

I will try to explain this in a very simple manner. Just remember that,

                                                                         “Obstruction causes velocity to decrease“

(This is applicable for all control surfaces)

                                                        Fig. Right Aileron is raised up while Left Aileron is lowered down

  • Now, we want to Roll our aircraft towards right. So we control the Aileron with the help of transmitter (in case of RC Airplane), steering wheel in case of real aircrafts. 

          On giving the signal, the right Aileron is raised while the left Aileron is lowered down. For the moment, let’s focus on the Right                      Aileron. The control surface here as been moved up & now, this causes Obstruction for the Air !!

  • Because of this obstruction, the velocity of air in the upper part decreases and hence Pressure in the upper part increases. (refer RC Airplane Series-1) and this causes the Right wing to go down and left wing goes up and as an overall effect, we get the Roll towards right.

4. Elevator :

Elevator is connected to the horizontal stabilizer. The elevator is responsible to control the pitch of the Aircraft.

Working of Elevator :

Consider an example where we need to pitch up the plane (make the nose up !). In this case, when the signal is given, the elevator is deflected upwards. Now, again the air flow in the upper region feels an obstruction which lowers the velocity of air in upper region. This causes the Pressure in the upper region to get bigger. 

This results in the ‘pressing‘ of the horizontal stabilizer downwards. Due to this the nose of the aircraft (front part) rises up.

(Just consider a pencil and hold it somewhere

                                                                                       Fig. Elevator is deflected upwards

  • The process is the same for all, whether its the aileron, elevator or the rudder

Consider an example of pencil. It’s CG (center of gravity) is marked. So when we apply a pressure on the back side (FigP(a)), the front part (part which is ahead of CG) rises up (which we say here as ‘pitch up’) as it rotates about the lateral axis passing through CG (FigP(b))


FigP(a). Pressure is applied at the back end of pencil                                    FigP(b). Result of the application of pressure (Nose Rises) 

5. Rudder :

Rudder is attached to the Vertical stabilizer. It is responsible mainly for the Yaw motion of the aircraft. Basically, Yaw is like moving right and left in your plane itself !

Working of Rudder :

Consider that we need to move shift to left while being in the plane of the aircraft (i.e. just try to give nose a different direction)

  • When the signal is given such that you want your nose of airplane to move towards left, then the rudder also deflects towards left. Now the rudder acts as a obstruction to the airflow on that side. Hence velocity decreased. Therefore, pressure increased. The higher pressure causes the front part to move to left (in the geometric plane)

                                                                                                           Fig. Rudder 

6. Flaps :

Flaps are the Secondary Control Surfaces which help the pilot to have a stronger control and stability over the airplane. Flaps are situated besides the Ailerons. Sometimes, the Ailerons itself work as Flaps as well (in case of single servo for each Aileron **). In this case, we call those control surfaces as ‘Flaperons’ (Flaps + Ailerons)

You must have hear pilots saying “FLAPS ON !!” or “FLAPS DOWN”. This tells that the Flaps are to be deflected downwards. 

                                                                                                        Fig. Positioning of Flaps

We are very well aware of the Lift generated because of the Flaps getting deflected downwards. (Same as Ailerons getting deflected downwards) but there is an important factor to consider, which is ‘DRAG’

DRAG :

– There is lift, but there is also DRAG developed due to downward    deflection of flaps. Since, due to this, the contact between the airflow and the surface gets broken.

– This Drag causes the wing speed to decrease

  • For Landing, we need the plane to be slow moving since ofcourse it’s easier to handle a slow moving car than an fast one. So the drag component takes care of reducing the speed of aircraft while on the other hand we also have the Lift generated which combinedly gives a slow and controlled descent.

 

  • From takeoff point of view, we need Lift to be generated at lower speeds itself and hence Flaps are essential in this case as well.

Note that : “FLAPS UP” implies the retracting of flaps to the original position (no deflection)

The amount of deflection can be controlled based on the need with the help of control stick !!

Conclusion :

Through this article, We discussed about the Controlling of the Aircraft. Go through it slowly and try to visualize by yourself. You will definitely get it. In this Series, we will keep going step by step and gradually make the whole basic RC Airplane model. I hopw you enjoy this Series !!

Keep Learning !!

RC Airplane Series – All Articles  (You are at Part – 2 !)