These seven segment displays are managed by an extra Arduino embedded in them. As a result, far less wiring and code is required for your project, since it is all encapsulated in this nice package. Here is the finished project:
This is a tutorial on how to build a clock display using only an Arduino, a Shift Register, and 4 digit seven segment display.
The end result should look something like this mess:
This is a longer range version of the GP2Y0D810 Infrared Sensor. They're about 15$, and work fairly well for distances between 0.5 meters and 1.5 meters. It is important to note that the distance to voltage curve is not linear. So, if you want the real distance, measured in mm, you'll need to come up with a best fit curve based on some experimental data.
Like the midrange version, the wiring is easy. Red goes to +5V, Black goes to GND, and white goes to an analog pin (in my case A0). You can even hook multples of them up as long as you use a seperate white to analog pin.
Again, IR does not the same on all surfaces. It depends on their reflectivity. For example, black surfaces tend to appear to be really far away since they don't bounce back much light. So, when you gather your data to make a best fit curve, you should use a surface similar to the one you plan on detecting.
The Arduino IDE has a lot of nice features. It's so easy, it's really one of the main reasons why you would choose to buy an Arduino over other options. It can be annoying sometimes though. If you want to distance yourself from the IDE, but still like the Arduino plaform, it's really as easy as just making a really simple text file and running "make".
By getting a command line interface, you can also automate the build and upload process. You can detect ports, or upload to multiple Arduinos at once.
When you use delay or delayMicroseconds in Arduino, nothing else can happen until the delay is finished, which can be a huge problem if you have more than one thing going on simulteneously, as will always be the case when building a more advanced robot.
Imagine that you want to check a sensor once a second. Easy enough. Just delay then check the sensor. What if you want to blink an LED on and off every 40ms, but still checking that sensor. Any delays used by one will mess up the timing on the other. If you delay one second after checking the sensor, the light will not blink during that time. You could make a fixed number of blinks between sensor checks, but that is inflexible and accumulates error.
Infrared sensors are a form of distance sensors. They tend to be more susceptible to inaccuracies. This is because they send out infrared light and wait for the light to tell distance. Certain colors, especially black, absorb some of the infrared light and may return a false reading.
This was tested on a variety of objects that were what would be considered black. A reading was obtained from almost all of the tested objects, although the distance returned varied. There was one black object that the sensor could not detect at all. The moral of this story is do not rely solely on infrared sensors for distance detection. Redundancy is key when working on robots.
For the GP2Y0D810 sensor, Pololu makes a breakout board that has three pins on it: VIN, GND, and OUT.
The HC-SR04 distance sensor is an ultrasonic sensor that is used for distance measurements.
Ultrasonic sensors work by sending out a sound wave and waiting until that wave bounces back to the sensor. This means that the sensor's accuracy can actually change with the speed of sound. However, this is usually not an issue.
This is a cheaper alternative to the Ping sensor. Instead of three pins, it has four: +5V, GND, Trigger, and Echo. This means that one less pin is available on the Arduino, but, depending on the project, that may not matter.
Parallax's Ping))) sensor is an ultrasonic sensor that is used for distance measurements.
Ultrasonic sensors work by sending out a sound wave and waiting until that wave bounces back to the sensor. This means that the sensor's accuracy can actually change with the speed of sound. However, this is usually not an issue.
The advantage of the Ping sensor over similar ultrasonic sensors is that it only has three pins: +5V, GND, Trigger. This means that one less pin is used on the Arduino, which may be crucial to a project.
XBees are a very simple way to enable wireless communication. Using wireless communication will expand the possibilities of a project, and is practically a necessity for a robot.
Two types of XBee communication that will be discussed are Arduino-Arduino communication and Arduino-Computer communication.
XBees cannot both send and receive data at the same time. If caution it taken, data should not be lost due to this fact.
It is possible to chain Arduinos together in such a way as to get communication between the two. Having Arduino-Arduino communication can be useful for many projects, such as having one Arduino to run motors and having another sense the surroundings and then relay commands to the other Arduino. This can be done in several methods, using I2C and Serial, to list a few.
This tutorial will focus on Arduino-Arduino communication through the serial ports (RX and TX).
