Introduction

The BeagleBone Black is a very powerful and affordable microcontroller - superior to an Arduino Uno in a lot of ways. It's fast enough to be used as a desktop computer, yet it has more pinouts than an Uno. With the BeagleBone Black priced at $45, it's really a great value compared to an Arduino ($35) or even a Raspberry Pi ($35).

An Arduino, while power-efficient and reliable, is incapable of high performance use cases like image processing. Even the ARM based Arduino Due is thousands of times slower than the BeagleBone Black. It can't even parse a JPEG (the library won't fit in the flash). A BeagleBone or Raspberry Pi, however, can easily process live streams from USB webcams and OpenCV.

The BeagleBone Black is significantly faster and more capable than the comperable $35 Raspberry Pi Model B. Both have the same RAM, HDMI out, and Ethernet, but the BeagleBone Black has superior IO (more and faster) and has a faster processor capable of running Ubuntu, where the Raspberry Pi cannot due to its older architecture. Remember, Raspberry Pi was intended to be an educational tool to teach kids to program, not to help you hack together a robot. The BBB has two extra processors dedicated to effectively manage the pinouts.

The downside? The pre-installed OS (Angstrom) at this point in time will break if you do a package upgrade. Not only will it never boot again once it finishes updating, but it also uses too much of the /tmp/ filesystem and stalls halfway though. You can run Ubuntu on it, but there isn't much of a point, since it's basically incapable of having a desktop UI or using OpenGL as far as I can tell. There's no reason why it shouldn't be possible. In fact, LXDE and XFCE sort of work.  This leads to the bigger problem. The documentation, support, and community behind BeagleBone is nowhere near that of the Raspberry Pi, let alone Arduino (which has the best by far).

Introduction

Who hasn't wanted to monitor what goes on when they aren't there. When I was little, I was always curious about whether or not anyone was going into my room and would have loved a camera monitoring system. It may even be a good idea to have a simple security setup for an apartment.

This tutorial shows how to set up a PIR sensor along with a small TTL camera and an SD card to capture images whenever there is movement in the monitored area.

The necessary libraries are: SoftwareSerial (for the camera) and SDFat (for the SD card).

Indrocution

 These parts are designed to be used in a quadrocopter. They are sold as replacement parts to pre-built quadrocopters, but work well as interchangable parts. This is documention on the specs and how to use the parts, since none is really provided.

I have modelled these parts in Creo Parametric. However, since I am using the student edition, it would likely be uselless to anyone who wants the part for their own project since it supposedly will only work with other student licenses. Furthermore, I'm not sure the license would even allow me to do that. I am not aware of a reason why I can't show you the results of the model like diagrams and renders though.

Introduction

To use Python as a graphical interface for an Arduino powered robot, programmatically read the USB with the pySerial library. However, waiting for input from pySerial's Serial object is blocking, which means that it will prevent your GUI from being responsive. The process cannot update buttons or react to input because it is busy waiting for the serial to say something.

The first key is to use the root.after(milliseconds) method to run a non-blocking version of read in the tkinter main loop. Keep in mind that when TkInter gets to the root.mainloop() method, it is running its own while loop. It needs the things in there to run every now and then in order to make the interface respond to interactions. If you are running your own infinite loop anywhere in the code, the GUI will freeze up. Alternatively, you could write your own infinite loop, and call root.update() yourself occasionally. Both methods achieve basically the same goal of updating the GUI.

However, the real issue is making sure that reading from serial is non-blocking. Normally, the Serial.read() and Serial.readline() will hold up the whole program until it has enough information to give. For example, a Serial.readline() won't print anything until there is a whole line to return, which in some cases might be never! Even using the after() and update() methods will still not allow the UI to be updated in this case, since the function never ends. This problem can be avoided with the timeout=0 option when enitializing the Serial object, which will cause it to return nothing unless something is already waiting in the Serial object's buffer.

Introduction

  

An IMU is something used to detect primarily orientation, but is a general term for an Inertial Measurement Unit. Needless to say, they can provide some vital information for mobile robots. In particular, flying robots need them since there is no way to guess orientation using wheel encoders.

An advantage to having an all-in-one unit instead of just using each of its sensors yourself is that the board can cross-check and merge the data for you. For example, a gyro gives you changes in orientation in each axis, but an accelerometer and magnetometer both send 3D directions - both in different directions too. Furhtermore, the acceleration doesn't even always point down.

One would hope that these sensors would be able to give velocity or even position information. Sadly, the sensors are just not accurate enough to be able to numerically integrate and avoid drift error. It can be possible to use the information to refine something that is capable of giving position information - like a GPS. That is partly why many of these boards include a GPS port. The other is that they are primarily used in flying drones, which usually want a GPS anyway and it is not too expensive to add the connector.

Backstory

I want to make a divergence meter. A divergence meter is not a real thing. It's a fictional device from Steins;Gate to tell if the worldline (timeline) has changed substantially from an original world line (the alpha) - following the time travel theory popularized by John Titor. If you've never seen the show, you might still be interested in how to wire up a longer string of displays to get 8 digits instead of being stuck with just 4.

Results

I could not really find any great Blender models of the Arduino Uno on the internet, so I decided to make my own. Mine was made entirely from scratch and does not use any image textures (except the wood in this demo). It features most of the details of the Uno, but does not have the printed circuitry. It was modelled off an image and some eyeballing for sizes, so it may not necessarily be to scale, but it looks close enough for Blender work. Even the text is there, using the default Blender font. The Arduino logo is actually a mesh of a circle. The most notable chips have the proper text on them, and the plugs even are shaped like sockets.

See the bottom of this post for the .blend files, or read more to see how it was done.

Pulse Width Modulation (PWM) is used because a microcontroller cannot easily send a specific voltages. It really can only turn a switch on and off. To be able to send a ratio of the current voltage, something like a variable resistor would need to be digitally controlled, but we don't have that. Instead, what PWM does is essentially flip the switch really really fast. That way the average voltage can be varied by leaving the switch on for longer or shorter than it is off.

Uses

A PD controller can be used in a real-time on a robot where a goal value can be both measured and controlled. A PD control is robust, which means that it can overcome unexpected behavior. 

For example, a PD controller could be used in the cruise control on a car. The driver decides the goal speed and the controller in the car could see how fast the car is going, since cars have a speedometer. Under ideal conditions, all it would take to maintain speed is to keep the engine throttled at a predetermined constant amount. However, many unforseable factors can change how much gas is needed to maintain speed. For example, the quality of the gas, engine temperature, road incline, and wind speed. A controller needs to be able to overcome these unpredictable or difficult to measure sources of error to maintain a given speed and accelerate or decellerate as needed.

Introduction

JavaScript is an actual programming language that is interpreted and run by your browser. It makes a webpage interactive and dynamic instead of just a rigid page that doesn't change once it's loaded. You can use it to send and recieve bits of information without having to load another page.  It allows you to drag and drop elements, or react to clicks and hovers. You can even use it to make an in-browser game.

It is syntactically similar to Java. It requires semi-colons at the end of each statement. However, it does not have rigid data types. Any variable can store data of any type - sort of like python. In fact, a variable can even store a function or actually contain nothing (undefined).