Hi, we are new to the VEX challenge and would like some advice so that we don’t make some major noobish mistakes.
Here are some questions that I have.
Our school has the old 3-wire motors and PIC microcontroller. Is it imperative that we upgrade to new technology?
Our teacher has stated that the competition we will be going to does not have an autonomous period. Also we will not have a field to practice on. What would be suggested in terms of adding shaft encoders/programming?
Does the gyro actually supply a reasonable angle that the robot is facing? or does drift make it useless.
At the moment we are not using clutches on our old 3-wire drive motors. Should we replace this?
How many people should be on a team? I suppose I don’t have much say in this to my school but the teacher has put us in teams of 2.
Any other advice to someone who is new to the VEX system and the VEC competition would be welcome.
Many times the rules of the competition require specific cpu or hardware limits.
A. Read the rules.
2. Best 1st sensor is a potentiometer for the arm, so you can move it to the right place every time.
3. Beginners don’t need gyros
4. With no clutches, you risk stripping internal gears. If you have motors to swap out, and have practiced swapping them out quickly, its not as much of a problem.
5. Team size depends somewhat on competition and scouting for alliance selection, and on number of drivers needed.
6. What is the VEC competition? Any pointers? There have been several beginners guides posted lately. One for drive, one for manipulators.
Re: PIC: Some tournaments only use VEXnet. If you have the PIC VEXnet upgrade (not sold anymore), this isn’t a problem. Otherwise, you’ll proabably want to upgrade sometime. (The World Championship only uses VEXnet.) The Cortex is much better (more motor/sensor ports, more memory/processor speed, video-game-style remotes, etc.), but it is a large expense to upgrade…
Re: Motors: The motors will work with either controller. However, it’s probably good to have a couple of high strength motors as well as the 3 wire type. They are a great addition to the VEX system.
Depends on you/your team’s current programming experience. I’d get to know how to use the programming software you have, at the very least so you can map buttons/joysticks on the controller to the motors on the robot.
Once you have a feel for how to control motors/joysticks in the code, I’d look into using limit switches to protect the motors on the arm or other parts as applicable. (i.e. don’t let the arm be powered if it’s at the end of its range, even if the joystick says to move.)
If you’re feeling ambitious, you could use an encoder or potentiometer to create preset heights (but that takes a bit of work to learn the first time…).
It’s reasonable, but you sometimes have to compensate for the drift.
Clutches will protect the plastic internal gears on the 3-wire motors from shock loads. In applications with a low torque load on the motor, they probably aren’t necessary. However, it’s advisable to use them in most applications. (I think…)
Personal preference. I’ll let others cover this…
Know the rules backwards and forwards. Studying the rules can expose hidden freedoms. It also prevents unpleasant surprises at the competition.
Document all of your work in a notebook. (pictures are good, too!) This really impresses the judges, who are often engineers or people with technical backgrounds. Keeping logs is done in the “real world,” and helps judges know how much work you put into the robot.
Watch YouTube videos of competitions. If you’re only going to a few tourneys (or even just one), watching videos lets you learn vicariously from other tournaments. Look for strategies you can use - this can give you an edge over other opponents.
At tournaments, have someone watch the competition - you need to know who to pick for the elimination rounds if you end up close to the top in ranking.
I know it’s easy to get lost with VEX, but it comes with time. I hope you have fun and learn a lot in your VEX career!
//Andrew
Thank you all (VEC is a typo )
I actually have a bit of programming experience, I know all the logic/math just not the language yet.
I’ll get clutches on our motors.
OK, a few more questions…
ahh, I’m sure I’ll think of something later
You’ve got some good answers to most questions, so I’ll just highlight a few:
#2. It sounds like your teacher has selected a competition – be sure that it’s designated to allow Crystals (old PIC controller). If not, some tournament coordinators may “flex” to allow crystals in a special circumstance (i.e., you’re a new team and have no Cortex equipment). Check with them in advance of the event. If so, you might need to bring your own crystals and tether cords (the curly phone cord connecting the base and the handset). If you have multiple teams using crystals, you’ll need a different frequency for each one.
#6. As you prepare for a competition, pace yourself and choose goals that are within reach.
Break tasks down into parts, and test each one as it’s completed. For example, driving base (chassis), lift, and grabber are 3 separate tasks. With 2 builders, you can work on 2 mechanisms at once and test them separately.
Build time will probably be double of what you expect, as half the time is spent in building a mechanism, and half the time is spent on making it RELIABLE - tweaking imbalances, reducing/increasing friction, bracing to increase stability, etc. It’s better to build a robot that scores reliably in the lowest 2 goals (floor and 11.5") than one that “kinda sorta” scores in all 4 goals but is so unreliable that it never actually scores a single point on the field. Building a lift high enough for the 30" goals is more time-consuming than building a driving base or lower lift, so be sure that you have enough time if you want to attempt this (estimate: 30 - 50 hours to build a reliable high lift the first time around).
Since your competition has no autonomous, probably the most important programming you’ll do is “mapping” your R/C channels to the motors. Be sure to program the channels in an “intuitive” way for the driver, i.e., pushing joysticks forward makes the robot go forward, not backwards. I agree that a potentiometer for measuring the rotation of an arm is the most useful of all the sensors.
Best wishes to your teams, and welcome to the community!
