Building Robots at School

October 15, 2011

Surface Mount Soldering Made (Sorta) Easy

Filed under: education,high school,teaching,Tech Ed,Technology — dtengineering @ 1:24 pm

I won’t say this is the simplest and easiest way to do surface mount soldering, but it is working great for me and my students. The trick is to use a very tiny amount of solder paste and a heat gun. The information, circuit board and code that you can download here will take you through the steps to build an SMD board with a PIC16f690, eight resistors and eight LED’s. It will use two capacitive touch pads and a neat little programming trick described in Microchip App Note AN1298, to work as capactive touch sensors. The code can be compiled and edited using Great Cow Graphical Basic.

The guide to surface mount soldering, as presented at the BCTEA Conference in Kamloops, is here.

Note: Links to the full-page printed circuit board and compiled HEX code will be coming shortly, WordPress is not allowing me to upload them due to “Security Reasons”.

September 17, 2011

Registering for VEX in BC: 2011/2012 Version

Filed under: education,high school,Robotics Competitions,robots,teaching,VEX — dtengineering @ 9:36 am

Its hard to believe, but we’re in to another season of VEX Robotics Competition, and all indications are that this year will continue the rapid growth that VEX has seen in the BC/Washington area over the past five years. New schools and organizations are jumping on board not just in the Lower Mainland, but across BC. Alberta has teams and tournaments starting up in Calgary and Edmonton, and team growth in Washington and Oregon promises to help keep the international aspect of our VEX competitions vibrant and engaging.

As part of this growth PYRS (the Pacific Youth Robotics Society) is hosting the first “VEX Ideas Workshop” today to help teams get excited about this year’s game and overcome some of the usual “What the heck do I do NOW?” questions that we’ve all faced in our first season of competition.

So, in some attempt at logical order… here are some steps that you might want to take at an early stage to help guide your team to global VEX Robotics domination.

1) You need a robot. I talk a little more about funding sources in this post. 

2) You need a place to keep the robot parts. I talk a little more about that in this post. If you’ve got a cupboard or back room to store an 18″x18″x18″ robot that will help. Keep in mind that if you start with one robot this year, you could have several more a few years down the road.

3) You need a team. Sometimes this happens before you get the robot. That’s okay, too. A team can take on some of the responsibilities for pitching PAC and admin to help with funding and with sourcing sponsorship and support from the community. Typically teachers will start with a robot club and announce it in their school bulletin. Don’t be surprised when 40 or 50 students show up and you’re wondering how you’re going to manage this with just one robot kit. This is a great way to show admin that there is a demand for robotics at your school and while it is a great problem to have… it is still a problem. If you can’t get more kits then spend a couple weeks working on design problems, studying torque and other important concepts and you’ll find that only the truly hardcore roboteers will remain. Typically a VEX team will consist of one robot and four or five students… but there is no set number. Feel free to be flexible… you have to be when you’re getting started!

4) Register your team. Go to and click on the orange “register a team” button. You’ll have to click on the “log in” button and then create an account. This will be the account you will use to register for events and register additional teams, so make sure you keep track of the password and details. Registration is $75 for the first team from a school or organization, and $25 for each additional team. All teams taking part in VEX competitions must have a registered team number.

5) Register for some events. If you see a label of “registration closed”, don’t panic… that just means that registration for this event hasn’t opened yet. Keep an eye on the events and double check a month or so in advance and you’ll find they are available then. Despite the fact that each event has an “event capacity” that cap is pretty flexible… we haven’t had to turn away a team yet. (Although that may change over the next few years as the number of teams keeps growing.) Note that for events outside Vancouver/Lower Mainland that PYRS typically arranges bus transportation, allowing you to travel in relative comfort on a nice highway coach. If you are on the PYRS email list, you’ll receive notification of upcoming trips.

Here are some  events you might be interested in:

 November 5, Redmond, Washington

December 10, Richmond, BC

January 27, Courtenay, BC

Feb 18, Edmonton, AB

March 9: BC Championships at BCIT “A” Division and “B” Division

Keep an eye out on the main registration page as other dates in Washington State will be added… and, depending on your team, those competitions in Hawaii, California, Florida and overseas might just tickle your fancy one day.

6) Get some game pieces to practice with. No… wait… read the game rules… then get some pieces to practice with. I’d say that the Goal/Object kit is more than sufficient to get started. Note that you’ll also want some foam tiles to practice driving on… but you don’t have to order them from VEX. You can find very similar foam tiles at hardware stores. One or two sets of tiles should be sufficient to get started.

7) Once you’ve got a robot that can move and manipulate a game piece, you might want to contact a nearby school with a full VEX playing field. In the past Gladstone, Cambie and Moscrop have all been more than happy to welcome visitors. Contact the teachers at these schools for more information… it will be a great experience for your students! (And you’ll have fun, too.)




June 6, 2011

VEX Workshops for Teachers: Spring 2011

Filed under: education,high school,robotics,robots,teaching,Tech Ed,Vancouver,VEX — dtengineering @ 2:54 pm

For the third consecutive year the Pacific Youth Robotics Society (PYRS) is pleased to present VEX workshops for teachers. This year, thanks to partnership with the BC Year of Science Initiative and our partners in Courtenay and Summerland we are able to offer more opportunities for teachers to learn about VEX and how competitive robotics can benefit their students.

The workshops will introduce teachers to robot design, sensors and programming using the VEX Robotics system and highlight design challenges arising from this year’s VEX game, Gateway. The instructors will be Todd Ablett, who has built the Gladstone Secondary robotics program into the largest and most successful high school robotics program in Western Canada, and Jason Brett, an eight year veteran of robotics competitions and instructor at the British Columbia Institute of Technology. The workshops are interactive and hands-on.

The time, place, and cost of the workshops are:


Gladstone Secondary School
Electronics Shop
Thursday, June 23 and Friday, June 24, 2011
9:00 – 3:30


Summerland Secondary
Monday, June 27 and Tuesday, June 28, 2011
9:00 – 3:30

Workshop Fees and the “Professional Learning Package”

Fees are payable at the beginning of the workshop by cheque in Canadian funds made out to:

Pacific Youth Robotics Society
2528 East 8th Avenue
Vancouver, BC
V5M 1W2

There are three fee options (all prices include HST):

$75     Basic Workshop Package
You are expected to bring your own robot and programming software, or make arrangements in advance to share with another participant.
$175   Basic Workshop Package plus Robot Rental
You will have use of a robot kit for the two-day long workshop. You may share this robot with up to one other individual.
$1,000 Professional Learning Package
You will leave the workshop with a complete VEX Cortex robot kit, manuals and software to continue experimenting and designing over the summer. There are sufficient additional motors and parts included to form the basis of a competitive VEX robot for use during the competition season so you can gain a deeper understanding of robotics as your students experience the thrill of robotics competition. Thanks to the strong Canadian dollar and excellent pricing from iDesign solutions we are able to include the robot, workshop, manuals, shipping, and programming software for the lowest price ever. Note that due to shipping requirements we need confirmation of your intent to purchase the Professional Learning Package by June 10th. Please let us know if you are interested, but cannot meet that deadline.


Registration is now closed for both workshops. Thank you to all our particpants for making these workshops an ongoing success!

Thank you also to our sponsors at:

March 30, 2011

Tethered Mini Sumo Robots

For years now I have been building tethered mini-sumo robots with my junior secondary students.  The robots are a fun way to discuss traction, torque, power, gear ratios, and a raft of other important engineering concepts that all actually come into play in a final competition.  The video on this page represents one of my earlier classes to build the robots, and since then we’ve added a few more rules to make the final projects look a bit better.  For instance I now ban exposed batteries and weights, and limit tape to being used for electrical insulation only.  I also use a piece of welding rod to support the tether wire, as you can see in the very slick looking robot with the rounded front in the video.  We’ve also upgraded to cast polyurethane tires, which give much better coefficients of friction than these store-bought tires do.  The key rule for all mini-sumo robots is that they have to measure less than 100mm long and 100mm wide in their starting position and weigh less than 500g.  To ensure a fair competition in my class, all students start out using a Tamiya Dual Motor Gearbox or a Twin Motor Gearbox.  For more details on where I source materials, and how I implement the project, check out my Tethered Mini Sumo lesson plans and Mini Sumo Design Tips

In the event the video does not show up, try this link:

Mini Sumos can be a lot of fun… give them a try!

June 22, 2009

VEX Workshop: Drive Systems

Filed under: education,FRC,high school,robotics,robots,teaching,Tech Ed,VEX — dtengineering @ 10:42 pm

This Wednesday through Friday the Pacific Youth Robotics Society (PYRS) will be hosting a VEX workshop at Gladstone Secondary.  I’ve been fortunate enough to get to do some of the organizing for the event, and will be presenting on a couple of topics, one of them being Drive Systems.  Rather than provide handouts (I haven’t figured out how to get video on to handouts), here are some links to what I think are great examples of ways to move your robot around.

SKID STEERING (aka Tank Drive, Bulldozer Drive, etc.)

In skid steering the axles remain fixed in orientation relative to the robot.  The robot is turned by making the wheels on one side of the robot turn faster than the wheels on the other side of the robot.  This is pretty much the simplest and most reliable way to turn a robot, and offers the advantage of being able to make a “zero radius” turn (turning on the spot) by driving the wheels in reverse on one side and forward on the other.

While “skid steer” sounds simple… and is in most applications… it is important to remember that for skid steer to work, the wheels, or treads, must be able to skid as the robot rotates.  If your tires have too much traction, you might not be able to skid… and thus unable to turn.  It happened to us with our very first FRC robot… it turned GREAT in the shop on a cement floor, but when we got to Toronto and put it on the carpeted playing field, our big grippy rubber wheels wouldn’t skid!  The robot would buck like a bucking bronco as the frame twisted under the stress of trying to turn, but until we managed to wrap pool vacuum tubing around the rear wheels and reduce their co-efficient of friction, we weren’t doing anything that wasn’t in a straight line.

Skid steering is the most common form of steering, and doing it right is important.  I’ll put more detail into a later post, but until then, here’s a great video of skid steering in action.  Notice that with just two wheels on the ground that there is no skidding, and how by shifting the centre of gravity, the driver is able to shift all the traction from the rear wheels to the front wheels.  It works the same way in robots…


Swerve drive involves wheels that actively steer by changing orientation relative to the robot body.  In other words, a car is a swerve drive system because the FRONT two wheels change direction relative to the car body.  (Cars use an Ackerman Geometry and a Differential to do this smoothly.)  A forklift is also a swerve drive, because the REAR wheels change direction.  And yes, I know some cars have four wheel steering… but they only turn their rear wheels a little bit.

Robots, however, can have pretty extreme swerve drives, in some cases rotating all four axles over 180 degrees!    In the FIRST Robotics World, one of the masters of the swerve drive are Team 118, the Robonauts.   An interesting thing to note on this robot, is that they had to build a swivelling turrent… because in their design all the wheels ALWAYS point in the same direction… allowing the robot to instantly head in any direction without turning, but ironically making it quite difficult to actually turn the robot!  Sometimes you will see this referred to as a “Crab” (or “Krab”) drive, because of the way the crab like movement of the machine.

While a crab drive like the Robotnauts requires a fair bit of work to design and build, with a VEX Robot you can simply use the VEX Swerve Drive kit to get started.  Or you can build your own….


Here’s a great video showing some different Omnidirectional Drive systems produced by FIRST Robotics team 115:

Using Omniwheels

“Omni” means “all”, so here we are talking about drive systems that allow your robot to move in all directions.  Omni drives have three “degrees of freedom”.  In three dimensional space an object can have up to six degrees of freedom:  Translation (movement) along the x, y and z axes, and Rotation (turning) about the x, y, and z axes.  A typical skid steer system has two degrees of freedom… translation along the x (forward and backward movement) and rotation about the z (vertical) axis.  A crab drive system, like the Robonaut’s machine mentioned above, also has two degrees of freedom:  translation along the x and translation along the y.  The robonauts can’t “turn” however, so they have no rotational degrees of freedom.  The VEX robot, in the video, above, has three degrees of freedom: translation in x and y, and rotation about z, making it an “omnidirectional” robot.

There are other ways to build an omni-directional drive system, however.  One of the most common ways is to use the omniwheel.  While my favorite use for “omnis” is to make it easier to turn a skid steer system, they also have some interesting possibilities for building omnidirectional drive systems.  There is a great powerpoint presentation on the different designs and the math behind making them work at the WPI FIRST Robotics Resource Centre.  Look for the third item on the list by Baker and Mackenzie.  Here are a few examples of the fun you can have with omni wheels:

A VEX Holonomic drive robotA larger, six wheel drive omni drive system.  “Holonomic” is often used when referring to a drive system using four omni wheels, with two wheels perpendicular to the other two wheels, however it could be used to describe any omnidirectional drive robot as they both mean, roughly, the same thing.  In the first video the wheels are angled 45 degrees to the frame and located at the corners of the robot.  It is sometimes easier to put the wheels in line with the outside of the frame, and at the middle of each side of a rectangular robot, or to use six wheels as in the second video.

When you build an omnidirectional robot with three omni wheels (see team 115’s video, above) it is commonly called a “Kiwi” drive.  The Kiwi drive has the advantage that because the wheels are based in a triangle that all three wheels are always in contact with the ground.  With a four wheel (or six wheel) system it is possible for one of the wheels to lose contact with the ground.  It is very important that when using omniwheels or mecanums (see below) that all the wheels stay in constant contact with the ground.  This is why many people advise building a suspension system for four wheeled omni-drive systems and/or restricting them to flat, smooth surfaces.  In VEX competition, however, the “suspension” is actually provided by the soft foam tiles of the playing field.  An alternative to the Kiwi drive is the Killough drive… which works like a Kiwi, but without using omni wheels.  Take a look here for some good graphics showing the vectors at work in making these robots move.

Using Mecanum Wheels

“Reinventing the wheel” is often used as a cliche to describe doing something needless or useless, but in 1973 a Swedish inventor did just that.  The mecanum wheel is quite similar to an omni wheel, but has the “rollers” around the outside of the wheel mounted at approximately a 45 degree angle to the axle.  This means that you can build a robot with the wheels set up parallel to the frame, but still have all the mobility of an omni wheel system with the wheels set at an angle to the frame.  This simplifies frame design and allows the added benefit of being able to switch back to skid steering by replacing the mecanums with regular wheels (also known as “traction” wheels).  These benefits encouraged our FRC team to use mecanum wheels in our 2007 FRC robot.  This robot has to be the most fun to drive of any of our machines, although it was by far the most challenging to program… and getting it to climb an incline took some careful work and driving practice.  We tried to make sure that, as much as possible, the amount of weight supported by each wheel was close to equal, and rather than building a suspension to keep the wheels in contact with the ground we just left a bit of flex in the frame.  In hindsight, we would have had a more competitive robot if we had gone with a simpler skid steer system and used the time we spent programming the mecanum wheels to work on other robot systems, but on the other hand… watching this machine move was just too cool!

The advantages of an omnidrive should be apparent… unlimited mobility on smooth surfaces, and a machine that makes people ask “How does it DO that?” as it strafes off to the side without turning.  In addition to being infinitely cool, omnidrives are also an excellent opportunity to teach vectors, forces and feedback.

That, however, is also the disadvantage of an omni drive system.  They are complex.  Swerve drives tend to be complex mechanically, while mecanum drives add complexity to the software.  It can be difficult enough to make a skid steer robot travel in a straight line, but the flexibility of an omni drive to go in any direction also means that they can go in any wrong direction quite easily.  On our mecanum robot we had encoders on each wheel, and a PID software loop to control the speed of each wheel to ensure that the robot would go straight.  Other teams have used gyroscopes to make sure their robot trackeded in a straight line, or potentiometers, for swerve drives, to make sure that their wheels all point in the correct direction.

Omnidrives also tend to sacrifice some “pushing power” to skid steer systems.  The swerve drive sacrifices the least (almost none, in fact), as all the wheels are driven and always point in the direction of motion, but omniwheels and mecanum wheels not only have a lower coefficient of friction relative to a traction wheel, but at times will only have two of the driven wheels pushing in the direction you want to go.  The idea behind an omnidrive, however, is that your added maneuverability allows you to avoid pushing matches by outmaneuvering skid steer robots.  This requires a sufficiently open playing field for the robot to navigate freely, plus a sufficiently talented driver to maximize the opportunities presented by the omnidrive.

Omnidrives aren’t always ideal for robotics competitions… but they make for a great programming or building challenge for an experienced robot builder and are some of the most exciting robots to watch that you will find anywhere.  If you haven’t built one before… why not give it a try?

*** Check out the comments, below.  Rick pointed out a great holonomic VEX robot that did really well at the World Championships, and I’m sure other people will post links to their favourite omni-drives as well. ***

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