Affordable, highly expandable combo for the new or experienced robotics enthusiast!
The Arduino controller has been the hottest item in the world of embedded controllers for hobbyists over the last few years. This article is a review of Parallaxs new Arduino Board of Education (BOE) Shield for their Boe-Bot robot. With this shield you can now control the Boe-Bot with an Arduino! Note: Shield is the name given to daughter cards that plug into an Arduino controller board.
Parallaxs Arduino Shield mounted on the Parallax Boe-Bot
The mechanical design of the Parallax Boe-Bot is one of my favorite kits. Its very robust mechanically, almost impossible to assemble incorrectly and works well. Its programmed with a Basic Stamp which was revolutionary in its ease of use when it was introduced in the 1990s and is still popular today. The BOE shield is a great addition enabling access to this robot base for the Arduino community.
If you have an existing Boe-Bot its easy to perform an Arduino brain transplant. Simply remove the four bolts holding the existing Basic Stamp based controller board and replace with the identically sized BOE Shield. Then attach an Arduino to the pins on the bottom of the Shield. You can purchase the Shield from Parallaxs online store and provide your own Arduino board. The Arduino is available from many online sources or even a local Radio Shack.
Arduino Board of Education Shield details and layout
If you dont already have a Boe-Bot then you can purchase only the parts you need; i.e. no need for the Basic Stamp board. Parallax sells a bag of parts that has everything in the Boe-Bot except the Basic Stamp and controller board for $82. Also get the BOE Shield (price not yet set). Add an Arduino UNO ($30) and youve got everything you need for about the same price as the original Basic Stamp based Boe-Bot ($160). Starting for scratch, you can assemble the Boe-Bot and run your first program in a couple of hours.
Original Basic Stamp Board of Education
BOE Shield Description
The BOE Shield has a similar layout to Parallaxs Basic Stamp BOE circuit board. There are four 3-pin connectors at the top left of the board arranged as two sockets each with 2 x 3 pins. The 3-pin connector carrying ground, 5V and signal using black, red and yellow or white wires is an industry standard for connecting servos. So its really easy to connect a servo to the Shield. These connectors overcome one of the weaknesses with connecting peripherals (sensors or servos) to an Arduino. You cant simply connect a peripheral via an input/output pin to the Arduino; you also need to connect to the power and ground pins. The Arduino board only has one power pin and two ground pins which is not enough for multiple peripherals; so youll need a mechanism that provides multiple power and ground pins. Several sensors e.g. the PING))) Ultrasonic Distance Sensor also use an identical 3-pin connector.
Battery case mounts on the bottom
You cant control a motor by directly connecting it to output pins from an Arduino because these pins are designed for powering other low-current logic (i.e. a 0 or a 1) signals. You need an external circuit that boosts the voltage level and current carrying capacity. Servos are nice because this external circuit is integrated into the servo. A servo normally has about 90 to 130 degrees of movement. You control it from an Arduino by specify a numerical value representing position. The servos in the Boe-Bot have been modified for continuous rotation (CR) where the numerical value now represents the direction and power (speed) of movement.
Electronic components for building electronic circuits on the Boe-Bot. Note chassis frame on upper left
Theres a small white 10 x 17 pin breadboard for prototyping electronic circuits. The black connector strips on the top, left and right side of the breadboard contain all the pins from the Arduino board. Theyre nicely labeled in the white lettering on the board making it really easy to connect to the Arduino.
The center of the board contains hefty 5V and 3.3V power supplies. Theyre used for powering the breadboard and servo connectors. They have much higher capacity than the 5V and 3.3V supplies integrated into the Arduino which are too small to provide 5V power to the servo.
The three position slide switch settings are (1) off, (2) power to breadboard only and (3) power to breadboard and servos. This is convenient for testing as you can test your software without power to the servos so the Boe-Bot doesnt move and then only provide power to the servos after you think your program is working. The battery power connector is wired directly to the Arduino board so the BOE Shield cannot turn the Arduino power off; you have to disconnect the battery connector.
Buffy Thinks its Lick Smacking Good.
Co-authors Roger Tang and Moez Janmohammad
The Arduino connects to the bottom of the board through the long pins that extend through the board from the two strips of horizontal connectors. The connectors at the top of the board allow you to stack another Shield on the top of the BOE Shield.
The reset push button replicates the switch found on an Arduino which is no longer accessible and covered up by the BOE Shield.
Arduino boards have a user programmable LED connected to pin D13. Its blocked by the BOE Shield and no longer visible. A small point, but I wish Parallax, had copied it and mounted a LED on the Shield as well like the way theyve duplicated the reset switch.
I was able to run my robot using the standard 4 x AA battery box. But Parallax recommends that you use their optional Boe Boost with the BOE Shield; it adds a fifth battery.
Note the sizes of the Arduino vs. the new Arduino Shield it is mounted to
Boe-Bot More than a Robot
The Boe-Bot is far more than just a robot. Its a great tool for easily learning lots of basic electronics. The BOE Shield has a small breadboard on it thats used for easily prototyping electronic circuits. And the Boe-Bot kit comes with a large handful of electronic components (LEDs, resistors, capacitors, phototransistor, piezo speaker and wires) for building these circuits.
Parallaxs Robotics for the Boe-Bot is a 300 page book that provides numerous projects and experiments that use these components. Theres about 50 hours of fun if you do all the projects. This book was written for the Basic Stamp version; at the time of writing this article, Parallax was hard at work at creating a similar version focused on the Arduino.
The combination of simple, easy to build electronics circuits coupled with a computer that controls them, is one of the situations where 2 + 2 = 5. For example:
1 Building a circuit to turn a LED on or off from a switch is boring. But when you wire the LED into your Arduino computer and program different LED behavior flashing, pulsing, etc from a small about 10 lines of code computer program its neat.
2 Similarly, its thrilling when you start with a simple circuit to move the coil in a speaker in or out. Then write a program to repetitively move it in/out very fast and you get a tone. Then vary how fast you move it and you can play different notes. Now string several notes together and play a song. This is exciting!
3 Build your Boe-Bot so you can individually turn on the left or right motor. Build a circuit with a photo resistor to measure the intensity of reflected line. Combine both of these with another simple 10 line software program and your robot can now follow a line. Way cool!
The programs to do the three functions above are literally all only about 10 lines long. Thats one of the things thats so neat about an Arduino; its really easy to program.
I suspect that the breadboard, along with the detailed instructions on the different projects you can do with it, is why Parallax named their Shield the Board of Education.
BOE Shield top detail view
Sparkfun, a popular online hobbyist electronics store, sells a somewhat similar kit containing a breadboard, an Arduino and a slightly different mix of electronic parts for $95. It doesnt have the parts to build a robot and the instruction manual is only 40 pages long. Both the Arduino Boe-Bot and Sparkfuns Arduino Inventor Kit and great for learning to use an Arduino and for learning some basic electronics. They both provide similar value for dollar; the higher priced Boe-Bot is offset by its higher functionality i.e. you can build a robot from it!
EXPANSION VIA MULTIPLE ACCESSORIES
Parallax sells many optional sensors that connect to a Boe-Bot to add new functionality. One of the most popular is the PING ultrasonic distance sensor. It simply connects via one of the Shields 3-pin connectors. The PING sensor detects objects that are a few centimeters to a few meters away and can be used in your program for obstacle avoidance.
Arduino and Parallax Shield with mounting hardware
Other available sensors include acceleration, gyroscopes, temperature, humidity, compass, pressure and even GPS.
This review has not covered the software programming of an Arduino. But its easy. Theres another article in this issue that covers the experience of two novices as they learned to program with an Arduino. Check it out for more details on software.
The Parallax Arduino BOE Shield coupled with the Boe-Bot robots hardware provides a solid base for several activities. Its a good platform to learn about an Arduino and to learn embedded programming. Its a good entry level robot. Its competitively priced with other similar robot and Arduino kits. If these topics fit your interest, I recommend it.
www.parallax.com, (888) 512-1024
Words by Dick Swan