VEX Robotics

localroger

While I'd always rather deal with our friends at Parallax, I found another company in a similar line of work which has some stuff in their lineup Parallax doesn't. Specifically, I needed a few rotary quadrature encoders for position control, and I really didn't feel like trying to print my own encoder wheels. A little GOOG led me to these...

http://www.vexrobotics.com/products/accessories/sensors/276-2156.html

Note that if you like those encoders, you'll need some of VEX's square matching shafts to drive them. They seem to be in more of a no soldering Boy Scout mode; they've built an Erector Set style system by which everything can be put together kit style, and without soldering for the electronics. They're more expensive than Parallax on almost everything that both companies build, but they've invested heavily in plastic injection molding and have some neat things (like my rotary encoders) that are quite hard to find elsewhere. In particular they have some nice gears, wheels, and general purpose metal shapes, and a couple of other sensors which would save a lot of work in some cases.

OTOH Parallax has them hands down in control logic (duh, Propeller?), power (Li-Ion?), other sensing (their version of PING requires the uC to do the pinging), and even motors; it will be parallax continuous rotation servos driving my VEX quadrature encoders. Still, I have VEX bookmarked for the day I find I really do need to build a rack and pinion actuator.

Franklin

I've used VEX in the past. For mechanical parts they have a lot of useful parts and assemblies. http://www.vexrobotics.com/products/accessories

ElectricAye

The nearby high school uses VEX for their "robotics" competition, but the "robotics" appeared more like radio-controlled teleoperators to me rather than robots. So I'm not sure what really defines robotics. One of the high school mentors mumbled to me something about switching to LEGO stuff, however, because LEGO competitions emphasized autonomous operation rather than this radio-controlled approach, and he thought the LEGO approach was more educational than the VEX approach. Either way, the kids get involved with machines and electronics and reality, so I don't want to split hairs. I'm guessing where VEX is really "behind the times" compared to Parallax and LEGO is in the sensor department.

localroger

VEX only offers two options for autonomous control, their ARM-based Cortex controller which is $250 and probably sucks battery like a toaster oven, and a PIC based controller that costs $150 (W.T.F.?) and probably can't walk and chew gum at the same time. It doesn't surprise me that a VEX competition would come out looking like an episode of BattleBots because their real strength is in the stamped and molded parts used to build the robot; for control logic they are spinning wheels.

W9GFO

The Vex robots are primarily operated by the students but there is a 20 second autonomous mode at the beginning of each match. Most of the work is in designing robots to accomplish the tasks required for the competition. It is not so dependent upon programming however there is plenty of opportunity to use clever programming for both the autonomous portion and when under control of students.

ElectricAye

W9GFO wrote: »

The Vex robots are primarily operated by the students but there is a 20 second autonomous mode at the beginning of each match.....

Just curious: is this part of the match heavily dependent on sensor usage? Or is it more of a blind set of programmed motions?

W9GFO

I'm sure there are many different ways to do it. The simplest being dead reckoning. It is common to use encoders, bump sensors and pots.

Peter KG6LSE

Vex is not in the same market . IMHO the BOE bot is Very cool but is not in the same class as far as mech Engineering as the Vex ... its a EE dream to hack but the frame is rather fixed . so for kids to make bot that is for overalll robotics games that is full of Mech adaptability ..
the $!50 Vex brain is C based and is TWO PIC s 32 bit . there are 3 levels of SW ...MP LAB to easy C ..
again more ROI as the same kit can teach "real dirty C "as well as drag and drop icons ..


the ASM and SPIN on the prop come close but are not here as a full BOE kit yet sooo ...

the VEX brain can be programmed over WIFI for years . I fact the college kids EG my team were the beta testers for VEXnet at the dallas world VEX games
.. it was SO handy !
sensors .. its a fixed competition so they ( VEX) make the challenge doable with the stuff they have ...

VEX FIRST and LEGO are for competitive team robotics... I would say the parallax stuff is for more task based and sensor and CODE robotics

As for the price .... Like parallax you pay for the convenience and the support of easy PBASIC . same with VEX .. its HUGE in HS and college . more users Of the same age and more is done to Fix things student to student ....

http://www.vexrobotics.com/products/accessories/logic/276-2170.html

http://www.vexrobotics.com/products/accessories/logic/276-2194.html
the prop comes close ....but again the EASY C is way more friendly then SPIN . for Kids

the headers are keyed ... batts are keyed .... the PIC brain used a PTC for motor protection .. IOs have series Resistors .....
the BOE is not protected to the same level. you can fry pins and Pooof stuff easy ..

Its for Mech design and Problem solving with a Fixed set of parts ...


my team MTSAC won the 2009 Excellence award for college VEX in 09.. and UNI robotics used a VEX brain for the master brain and it we won the gold at the ATMAE national conference Last weekend ! ( BTW parallax was a sponsor )
I chose the VEX as the main as a prop would have not had the super short programming lead time and the BS2 is not multy tasking .
I did the code in less then 6 Hours the night Before we left Iowa ..

localroger

Good info, Peter. I got the impression scanning the VEX website that their products are heavily weighted toward making it possible to do the builds without soldering or power tools. That's kind of a niche with a certain built-in market thanks to the schools, but it's also a dead end in that you always reach the limits of a system like that. Great for intro and for young people, but very limiting once you reach the edge of the VEX universe.

I see the main difference in capability is that Parallax started out doing practical controls (BS1) and branched out into sensors and hardware, and VEX started out with a major investment in mechanical manufacturing (including injection molding) and has mostly done standard electronics with little innovation except that they are well packaged and hardened against abuse. VEX can sell me a quadrature encoder for $10 because they do injection molding. Parallax can sell me an 8-core 32-bit IC for eight bucks because they made their own CPU.

Searider

I tried using the VEX system before moving to the propeller. My primary robot platform uses Vex for most of the mechanical stuff but I use a Prop for control. They have a great inventory of gears, wheels, structural parts etc that is very handy for modifiations and quick builds. Now that I have a machine shop in my garage, I don't seem to be using them as much but I still see VEX as yet another place that has some parts that are very usefull and hard to get other places. No reason not to integrate them into your system.

ElectricAye

I helped out at a Vex competition last weekend, first time I've ever seen the Vex stuff in action. I was impressed by what the kids were doing with the stuff, and the competitions look like great training for ER nurses and doctors - robots are always breaking and the kids might have only 30 minutes until their next competition, so they need to work fast. Everyone was either in a competition or always in the act of fixing their robot. I like the way the Vex stuff is modular. Also, they have a "Programming Skills" portion of the competition wherein the kid's robot runs a course and scores points using only its program (no joystick control). They have a number of sensors that can be integrated into it, too. I have no idea how fancy the Vex brain is, but it's surely overpriced, I think ($250).

Frankly, I don't see why you couldn't build a Propeller-based controller and use all the mechanical hardware to run some competitions of your own.