Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: robichgu on May 01, 2010, 07:37:27 PM
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Hello,
I just took an interesting mechatronic class where we got to program a sumovore robot with a renesas MCU. I do not know much about robotic as a hobby although I have a pretty decent background in C programming, sensor interfacing, microcontroller interfacing, matlab, control, etc. I want to know what would be a good robot kit for me to get so that I can keep going and have more fun. I was thinking about getting a Mindstorm Lego NXT but I want to make sure I will not be limited to using the LEGO sensors, servos, motors, etc. Also it seems to be possible to program the robot in C which I find quite interesting. Do you guys think that the lego NXT is a good choice ? Any opinion will help.
Thanks
Guillaume
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Follow the $50 robot tutorial. If you can handle that, it opens up a world of fun stuff.
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Hi,
I was thinking about getting a Mindstorm Lego NXT but I want to make sure I will not be limited to using the LEGO sensors, servos, motors, etc. Also it seems to be possible to program the robot in C which I find quite interesting.
There's a plethora of non-LEGO sensors on the net (made to work with LEGO).
Do you guys think that the lego NXT is a good choice ? Any opinion will help.
Even if I'm from the country of LEGO, I'd advice you to look at Vex (http://www.vexrobotics.com/) as well, as it seems to be a much better system for the purpose (LEGO tends to break apart unless you bond the pieces chemically) and the same stuff about sensors and programming applies equally to both (Vex uses a PIC processor in their "brain".
Either way, you don't need to use the controller made for the set, anything can be made into a LEGO- or Vex controller and you can thus just reap the benefit of a universal mechanical platform that you can alter as needed.
If, on the other hand, you have tools and machines for it, you can make your own from the button up.
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NXT has a better mcu, an ARM7, and a large graphic LCD that comes in handy to display sensor readings or even a Tetrix game. Lego is more flexible, allowing you to create more complex machines, but they will be small or mid size. Vex will let you create bigger and sturdier robots, but there are not as many compatible sensor on the market. But you can make your own for both NXT or Vex using I2C interface. I have learned robotics with Lego RIS set. I am glad I did, but I was also fortunate to find a close by group of enthusiasts that gathered every 3 months to do a new challenge. I have built around 40 Lego robots over 6 years, some of them being improvements of older designs, so I guess only 30 were new designs. I build "sheet metal" robots now (that's how AFOLs call non-Lego robots) but every time I need to prototype something mechanical, I do it with Lego.
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Hi,
NXT has a better mcu, an ARM7,
Fair bit of overkill IMO, as much less would do it, but hey, no complaints over getting the good stuff, just over the fact that they don't really bring out the powers of it :)
As I've learnt over the years, a good programmer can cram the impossible into a very small and slow controller and still get the job done, while a bad programmer just goes for the ultra fast controller with all the bells and whistles to make up for the fact that he's poor at programming.
Just like in modern computers - Once we wouldn't think that 64kB would ever be used to the brim ;D
And since controllers don't use GUIs, there's no real explanation for the wast increase in memory and speed besides sloppy programming.
What LEGO Nxt and Vex are meant for could be done with a baseline controller like the (outdated) AT89Sxx or similar, so when there's so much potential power, it's sad that they don't use it (or at least help those wanting to use it with relevant info - Oh, there is a LEGO developers group acknowledged and supported in some way by LEGO, but Joe Average...).
[...] but every time I need to prototype something mechanical, I do it with Lego.
Yes, the rapid prototyping situations is the strength of LEGO and to some extent Vex, but it is IMO a bit too expensive just getting it for rapid prototyping (LEGO Nxt cost more than the twice the US price here in its homeland >:().
With LEGO, you're more or less bound to using LEGO. With Vex, you can mix it easily with other materials, more like Mecano construction sets, but you have to bolt it all together, so it's not as quick as LEGO to assemble.
Unfortunately, it doesn't seem super strong either (judged from pictures and info found on the web), just like Mecano went downhill on strength somewhere around 25 to 35 years back - the "new" stuff appears to be made of recycled polish biscuit tins or similar, while the old stuff was substantially stronger (I have some from each "period" to compare with).
I recently stumbled over These sets from CapToy (http://www.captoy.dk/products/categories.aspx) on a Danish site. I don't know if this is sold worldwide. It appears to be made in China, but I haven't seen it anywhere else. It's much cheaper than both LEGO and Vex, but it appears to have somewhat crappy motor units.
That said, I wouldn't mind having a load of each, but as nobody just throws it at me, I think that I'll go for some Vex stuff if I ever get myself convinced that I can't live without it - exactly for the late night testing of ideas where you can't run power or air tools (as even a hacksaw would wake up someone).
I wouldn't consider their respective controllers or sensors though, as I can make it better, cheaper and right to the point of what I want it for; Like the sad 4 proportional + 2 digital (on/off) channels that Vex has for a ROV - doesn't go very far and is much too expensive.
Should anyone ever make something full metal (gears and all) and with a broad range of all parts, I'd be their first customer, but apparently, quality and stamina doesn't sell these days ???
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mindsensors: google it, you can buy them of off trossen and other online stories, I have a friend who bought a CMU cam for it which may work for it and there are other sensors