Bluetooth-controlled Car – Part 2

Now that the hardware was functional, I had to make it respond to input from the user. This had two parts: the Arduino software and the controller app on the phone.

Arduino Software

It took a bit of experimentation but I was finally able to run the motors at the correct speed. My aim was to create methods that moved the car front, back, left and right. And, of course, the all important stop command. To test it, I wrote a small program that invoked these methods and made the car go in all directions.

I then modified the loop to accept commands from the Bluetooth controller. Since all I read was bytes, I used the ASCII characters (‘f’, ‘b’, ‘l’, ‘r’, ‘s’) to denote the various commands that the car understood.

iOS App

For the app, I decided to use Swift. This was my first time writing an app and I ended up using the Internet as my guide! I learnt that iOS apps use the CoreBluetooth library. I ended up creating a BluetoothManager object that was responsible for detecting when peripherals were in range as well as connecting to them. Since I wanted the application to be seamless, I was going to have the app automatically detect when the car was in range and connect to it. The user could then send commands via the interface. I chose to use a Single View App as my base project. The app looked as follows:

Once the car was in range, the app would connect to it. The user could then use the buttons to send the car forward, back, left, right and stop the car if necessary. If for any reason, the connection to the car was lost, the user could force the connection by tapping on the Bluetooth icon. The app would only accept commands if the car was connected. You can see a video of the car working below:

 

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This is part 2 of my bluetooth-controlled car. You can read Part 1 as well.

Marvel Science: If you were hit by Captain America’s shield, would it kill you?

I recently re-watched Captain America: The Winter Soldier, in which Steve Rogers spectacularly throws his shield at his enemies to incapacitate them. Action scenes like those left me wondering: would the thrown shield’s impact actually kill those soldiers in real life? In the MCU, Steve throws around his shield like it’s no big deal, hitting villains left, right and center, but it’s always left unclear whether the impact leaves the villains simply unconscious or actually dead. To find out what would happen if one were caught in the crossfire of Cap’s shield, I took to physics.

To calculate the famous vibranium shield’s impact, I needed to first determine the shield’s physical properties, such as its weight. According to the Marvel Database, Captain America’s shield weighs 12 pounds (5.44 kg) and is 2.5 feet in diameter (0.762 meters). Now, I know what you may be thinking, “Captain America’s shield is made of vibranium, so doesn’t that change the values?” But, the problem with taking this fact into account is that we don’t know much about vibranium as an element, so it’s impossible to replicate those results in real life.

The simplest way to account for vibranium is to take into account exactly what we see on film. Using the incredibly powerful Open Source Physics software, I took various trials of Steve throwing his shield and tracked it to get various velocities (the gif below shows one of those). I then took all the values and averaged them out (which gave surprisingly similar results) to get a velocity of 18.77 m/s (~42 mph).

So, abiding by the rules that the MCU gives us, we have a 5.44 kg disk of metal flying at someone at 42 mph (18.77 m/s). Sounds pretty dangerous, huh? So, what’s happening to the poor guy that’s getting a full serving of justice? Well, let’s first look into energy. The formula for kinetic energy is \(\frac{1}{2}mv^2\) and using the values we got before we can find the kinetic energy this shield has. This value turns out to be 961.9 J. This is the translational kinetic energy. But when Steve is throwing his shield, it’s not only moving linearly but also spinning. That means we need to calculate the rotational kinetic energy of the system using \(\frac{1}{2}Iw^2\). To calculate this, we would need to approximately figure out the moment of inertia (I) of the shield and the angular velocity (w) of the shield. First, let’s determine moment of inertia.

So, Cap’s shield kind of looks like the top part of a sphere, if you were to chop off a slice of it. We know the radius of this shield and the depth of the shield, so if we can find the radius of the sphere the shield came from we can determine the moment of inertia. Take a look at the picture below for clarification.

To find the radius of the bigger sphere, we would use the Sagitta Theorem. Using this theorem, we take the sagitta (or the length from the top of the shield to the ground if it is lying flat) and the half chord length (the radius of the shield) and use it to find the radius. We do this with the formula \(s=r\pm\sqrt{r^2+l^2}\). This gives us the sphere radius of 0.8609 meters.

Now that we have the radius of the sphere, calculating the moment of inertia is a simple integral. Check out the picture for my work, but instead of boring you with the calculus, I’m going to tell you the value which is 0.645576 \(kgm^2\). Quick note, in this case, we’re assuming the shield is a thin shell as it is probably closer to the rules of vibranium than a shield with thickness.

Now, to find angular velocity. To do this, we need to go back to the videos. All I had to do was count the amount of times Cap’s shield rotated in a certain time frame. This was actually difficult for two main reasons: 1) Cap’s shield is going 18.8 m/s and 2) camera angles, but I managed to get a good estimate by counting the rotations in slow motion and then speeding the video back to normal speed and measuring the actual time it took to spin. Doing various trials got me an average angular velocity of 65.3 rad/sec.

Now, it’s another plug and chug situation. We take the formula from before (\(\frac{1}{2}Iw^2\)) and just plug in the values. This give us a rotational kinetic energy of 1376.40 J. Kinetic energy is additive, so we add the translational and rotational kinetic energies to get a total of 2338.30 J. That’s a lot of kinetic energy dispersed over a small area. But, to clarify this value, let’s take a look at the force that is applied to our unlucky villain.

To do this, we need to take a look at momentum. Because the time that the force is applied is constant, we can use the formula F = (\(\frac{mv}{t}\)). This formula comes from Newton’s first law (F = ma) as a is equal to v/t. To find the time Captain America’s shield is in contact with the person, I again took various shots to get an average time of 0.015 seconds. So, the average force that our man would be experiencing is a tremendous 6,818.13 N.

Now, to find the force on the guy at a specific point, we would use Ft = Impulse = Δp = FΔt. This might seem like we’re repeating the same steps as before but this time we are looking at the velocities directly before and after the collision. The average I got for an velocity right before impact was about 26.4 m/s and the shield’s velocity right after the collision was 5 .5 m/s using the Open Source Physics software once again. Here’s what’s happening:

So, Δp = p\(_{f}\) – p\(_{i}\) = mv\(_{f}\) – mv\(_{i}\) and if the left positive direction is positive, we can keep both velocities to be positive (both velocities are heading to the left). Now, mv\(_{f}\) – mv\(_{i}\)= (5.44 kg)(5.5 m/s) – (5.44 kg)(26.4 m/s) = -113.696 kg*m/s. This is the impulse of the man on the shield so the impulse of the shield on the man is 113.696 kg*m/s.

Impulse equals the force time the change of time so now force is easy to find. The average time of contact for the shield hitting the person is 0.021 seconds. So now we put that into the equation to get 113.969 kg*m/s = F\(_{N}\)(0.015 sec) to get a force of 7,597.93 N. That number makes total sense as it’s a 12 lb disk going 42 mph (5.44 kg disk going 18.77 m/s). To put that number in perspective, normal human being has a 25% chance of breaking a bone at 4,000 N of force.[note 1] The shield, which hits someone with 7,597.93 N, has a 47.48% chance of breaking bones which is basically taking a 50/50 chance at not getting hurt. But, one thing that we fail to take into account by these numbers is the shield is effectively hitting you at a single point, which in turn means a lot of force will  hit you within a small area. This means the shield is definitely breaking bones and if it hits anywhere on your body, you’re not going to be too happy about it and, well, you’ll probably be dead.

In conclusion, if you were hit by Captain America’s shield, you definitely would not make it out alive, so it’s better to not to take on the Star-Spangled man with a plan.

Notes:

  1. Brute Force: Humans Can Sure Take a Punch

Bluetooth-controlled Car – Part 1

For a few weeks now, I have wanted to find an interesting project where I could pair up my 3D printing skills with the Arduino. I also wanted to try something new and decided to combine it by writing an iOS companion app. This led me to deciding to build a electric car that could be controlled via the phone’s bluetooth.

The 3D Model

I wanted my car to look realistic so I did some research and came up with a design that was both practical and interesting. The 3D model would have two main parts: a base and the body. The base had to be large enough to house the motors, Arduino and the sensors. It would also need to have four grooves that would be used by the wheels. The design of the body was pretty straightforward as you can see below. I used some of the design elements from the real car I drive, a Honda Civic.

Base

Body

Both the base of the car and the body were designed using Fusion 360. Fusion 360 is a great program because it’s free and works well for creating basic shapes. I used photos of a car and using the line tools, created a sketch on top of the image. This sketch was the basic shape of the car and was then extruded out to create a basic car shape. Two holes were cut out (using premade cylinders) for the wheels and then details were added (with the premade shapes and shapes created in sketch mode) and altered in the sculpt mode. I had to cut my model in half because my print bed (a Lulzbot Mini) was too small for the size that I wanted to print at. Honestly, I wish I had a better way of dividing my model because the seam in the base became a issue when connecting the two halves. I had designed the model so the base would be able to fit snuggly underneath the body, but the tension was too great and caused a crack on one side of the model. With hindsight, I should have made the body a bit bigger to better accommodate the internals. Overall, it took about 14 hours to print the base and body of the car at a 0.25 layer height.

Putting It Together

While the internals of the car are not exposed, I wanted it to look clean. I’ve always been fascinated by the clean internals of Apple devices. I placed the Arduino microcontroller in the center of the base and surrounded it with the four DC motors. The motors had motor shafts on them which were then connected to the wheels. Lastly, the bluetooth module was mounted to the Arduino. The black tape below was needed for me to keep my two halves connected since I printed my design in two halves due to my printer bed size. As Adam Savage has taught me over the years, nothing duct tape can’t fix!

One of the tricky parts was making sure that the motors were connected properly to the motor shield. I had to orient the four wires as below:


Next was the bluetooth module to pair the robot with a phone. I chose the HC-08 for this project. The module had 6 pins, but I only needed to use the RXD, TXT, GND, and VOC pins. These pins connect into the Arduino in the respective pins (RXD → RX (0), TXT → TX (1), GNG → GND, VOC → 5V).

Next I attached the wheels and spent some time painting it using the colors of my favorite Marvel character, Iron Man. Finally, my car was ready!

In the second part of this post, I’ll detail the software components of the car. In particular, the iOS app that sends commands to the car and the Arduino software that interprets these commands and moves the car. Stay tuned!

Parts List

The Demise of Man

Prejudice is an idea that pre-exists in the minds of man and controls the actions that a specific person takes. Rod Serling’s words state that the thoughts that lie within a person, when built on the fear of the unknown, can be as harmful to society as war. When man allows his thoughts, especially those that are built upon paranoia, to lead him he begins to develop a distrust of the individuals in society, This, in turn, eventually leads to the collapse of a community. This idea can be tied into the views of Arthur Miller in “Why I Wrote The Crucible” and his own novel titled The Crucible. As Miller’s story evolves, we see how people suspecting others due to fear can drive apart a community and eventually leads to chaos. The concepts of prejudice by Rod Serling in “The Twilight Zone” episode entitled “The Monsters on Maple Street”  is supported by the ideas brought to light in The Crucible and the words of Arthur Miller in “Why I Wrote The Crucible.” Both gentlemen discuss how prejudice can influence the opinions of a person and lead to horrible consequences.

Serling’s discusses in “The Twilight Zone” how prejudice can lead to the eventual destruction of a community, and he illustrates this point in his episode “The Monsters on Maple Street.” This episode shows a town, which was once all friendly with each other, slowly tear each other apart as they become suspicious due to a paranoia of monsters living there. The idea seemed absurd, at first, but once unexplainable occurrences happen, it is no longer a ludicrous thought. One of the characters, Charlie, when asked to stop the viewing party on a man who is a suspected to be a monster, says that this suspicion would be nothing in normal circumstances, but this is an unusual circumstance, so the ideas of reality change ( “The Monsters on Maple Street”). Serling states, when referring to this episode,  “The tools of conquests do not necessarily come with bombs and explosions and fallout” and this is beautifully illustrated in “The Monsters on Maple Street” (Serling).

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Poems of Pi

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Download PDF Piscine Molitor Patel or Pi, a strong believer in God finds himself having to move from his home in India to the unknown place of Canada. However, tragedy strikes and Pi ends up being shipwrecked, alone on a boat. Or so he thought. Pi soon finds himself on the boat with a few […]

Social Hierarchy in India and Greece

Since Mesopotamian times, social hierarchy has influenced the role of individuals in society. In different civilizations throughout history, social groups were used to create a division of labor with hopes of increasing productivity. In Ancient India, the community was divided using a social caste system. This social caste system was very rigid and provided little room for movement. In Ancient Greece, however, a less rigid class system was used to divide the community. In both systems, position was determined by who your parents were; however, the class system did allow some upward mobility. Although they were from different time periods and geographic locations, the social structures of Ancient India and Ancient Greece were similar because they established a system of ranking people.

The earliest mention of the Indian caste system is found in the Vedic hymns, which are believed to be from around 6000 B.C.E.  In Ancient India, people were divided into four groups, or varnas: Brahmins, Kshatriyas, Vaisyas and the Sudras.[1] The highest caste in the Indian society was the Brahmins, who were teachers and priests. After the Brahmins came the Kshatriyas, they were the warriors and rulers in Ancient India. While the Brahmins were technically the highest group in the hierarchy, the Kshatriyas were closer in status to the Brahmins than the Vaisyas. The Vaisyas, who were the middle class, were skilled traders, merchants, and farmers. Next in the hierarchy came  the Sudras, who were the unskilled workers. They were mostly laborers and craft workers. The formation of these groups was considered decreed by Brahma, the Creator of the universe. The civilization of Ancient India believed that if one did his duty (dharma) within the caste he was born in, he would be rewarded in subsequent lives by moving to a higher caste. These beliefs led the Indians to accept their role in society without questioning or wanting to change it. [2]  Later  as time went on, a fifth group emerged who were referred to as the Untouchables, or the Outcasts. These individuals usually were responsible for jobs others didn’t want to do; they were the closest to slaves.[3]

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Freedom of Speech

Think before you speak! Be careful with your words. Speak wisely! We have been told since we were kids to be aware of what we say. We have been taught how powerful words can be and how we ought to be careful when using them.Our founding fathers also placed a great deal of value on our right to speak. So much so that they made it the first part of our Bill of Rights: The Freedom of Speech. Over the years, speech has evolved to include not only the printed medium, but to also include anything that has been said on the Internet. In fact, our proclivity to blurt out our thoughts before we can digest them, often leads to us writing things in an emotional state on sites such as Twitter, Facebook, etc. With this in mind,  many Americans wonder if the concept of freedom of speech should exist today. Our courts have be inundated with cases that address our right to free speech. So, how do the privileges guaranteed in the Bill of Rights – specifically the Freedom of Speech – apply to modern American Life? How do contemporary challenges to the Right to Free Speech affect the Constitution of the United States of America?

The first case I studied was the Lane v. Franks. This case involved a public employee’s fight for his freedom of speech in the context of revenge. Edward Lane was the director of the Community Intensive Training for Youth Program (CITY) at the Central Alabama Community College (CACC). In 2006, while auditing CITY’s finances, Lane found out that Suzanne Schmitz, a state representative who was on the CITY’s payroll, had never performed work for the program. Lane was told that, by contacting Schmitz and terminating her employment, he would bring negative attention to the CACC and himself. However, after Schmitz refused to work, Lane terminated her contract with CITY. In retaliation, Schmitz sue to get her job back. Steve Franks, president of CACC at the time, wanted to reduce the workforce because of budget cuts. In 2008, Franks sent termination letters to Lane and twenty-nine other CITY members who were under probation and served less than three years. However, a few days later, Franks rescinded all of the terminations except for Lane and one other employee because he claimed those employees were not under probation. Lane sued Franks because he argued that his termination was a result of his testifying against Schmitz during her trial. Therefore, his termination was a violation of his First Amendment rights.[1]

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Dangers of Cell Phone Radiation

This paper is going to talk about the dangers of cell phone and Bluetooth radiation. Cell phone radiation is a topic that most people overlook or switch to Bluetooth thinking that the Bluetooth emits less radiation. Well this is true but what about those people who are too lazy to take their Bluetooth out of their ears? Are they getting exposed to more radiation than others? When people start to talk about cell phone radiation, their audience gets really uncomfortable and eyes their cell phones warily. Then they end up either turning off their cell phones and its ends there. They never think about it ever again. But, using a cell phone does not mean death. However, using the cell phone a lot could result in brain tumor or blood cancer.

According to experts at the Oyster Creek Nuclear Plant, the human body itself is exposed to radiation levels every day. Even the food we eat, like bananas, are radioactive. So the average natural background radiation a human is exposed to 300 millirems of radiation per year.(A millirem is 1/1000th of a rem.)(Exelon, 2011) This doesn’t seem to bad, does it? So, why are we freaking out over this? Well, our generation tends to go over the  “average human radiation”. We use our devices more than the average human and we definitely watch more T.V than the average human. According to some experts from Oyster Creek Nuclear Plant you can either get an acute amount of radiation or the same amount over time. If you get an acute amount of radiation you can die or suffer death of cancer. So, by getting the amount of radiation over time, we do have to worry over that as much. (Oyster Creek Nuclear Plant)

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Should We Continue to Explore Space?

20080924_columbiaThe world would be a whole lot different if we didn’t explore outer space. In fact, a lot of the things we take for granted would not exist without the exploration of space. But, should we explore space?  The exploration of space is full of risks. An astronaut has a life of adventure and fun, but is it really necessary?  Do we really need to send people to outer space for the sake of our technology, or are we risking lives in the process of our gains?

So, why do we need to explore space? Some of the things like cellphones, power tools, digital imaging, weathering tracking, G.P.S, robotics and solar energy would not exist if we didn’t. Take the cell phone for an example. Towers send signals to your cell phone enabling you to be able to chat with your friends. New discoveries from the astronaut’s journey to space give us the chance to think about the fact that we are all together on this planet as one.

Now there are some negatives in the exploration of space. Take Apollo 1 for example. Apollo 1 never made it to space. While it was being tested, Apollo 1 broke out in a fire and killed all three crew-members  It was here that we saw the dangers of space exploration. We also spend millions of dollars on space exploration while risking the lives of our astronauts. Another thing, which is highly unlikely, is the chance of discovering other alien life forms. Are we ready for it?

It seems like there are good and bad reasons to go to space. We would love to know everything there is to outer space, but we can’t do that without risking lives. Astronauts know of the dangers, but their desire to learn more for us drives them. Plus, with the growth of technology, sending astronauts to space is a lot safer now thanks to a lot of testing. It seems like space exploration is the way to go.