Arduino buy help

Hi, I'm planning to buy an arduino kit. I'm participating in the robocup competition so my need from the arduino board are: Reliable (it's very important the the robot will preform consisted and won't do any unusual movements or even worse won't work suddenly), enough storage for large programs (I really don't know how much stroage will our program eventually take, but I believe that the 32 kb version is smaller). I would also need to connect it to 4 DC motors and 10 servos (and of all that system will run from a battery).

I believe that I need the mega, but from where? should I buy the original or are there's 3rd party sellers who sells even better boards and even in lower prices? Please consider that I need to buy a full kit with resistant, cabels etc. (lcd isn't important)

Thanks for your help.

I think the problem here is that you are talking about a project that is relatively advanced, advanced enough that to tackle this project you would normally already be able to answer these questions yourself. So, in general, good luck and start working early on it.

No Arduino from any vendor is going to be able to be a mission critical board, at least not without some additional work. I think with all these motors in the mix you are going to have to get familiar with optoisolators. Too many people have too many problems with Arduinos (and other microcontrollers) when using them in high current draw/inductive environments like this. Optical isolation between the logic and the power electronics helps a lot.

In terns of getting a larger number of outputs, I think your idea of using a mega is a good one. In terms of program space, you simply cannot know that until you have written your program and have some idea if it is going to fit or not. It may not even fit on the Mega. It's hard to say without knowing anything about your requirements. Though having 256KB of program memory is a tremendous amount of space for most embedded apps.

I have no idea what you mean by buying a full kit. I don't think you are going to find it. Cables in this case is probably just a nice big spool of hookup wire. Resistance may be needed in some places, but if you are limiting current to the motors via resistors you will kill your batters very quickly. Using some sort of motor driver that limits current intelligently via PWM is probably a better call.

Look at current Arduino robotic projects and base your hardware needs on what a similar project uses. Use Google to locate articles, such as this search.

I will warn you now that 4 motors and 10 servos can not be prototyped from a single kit... kits are for experimenters wanting to know basic concepts, one-by-one.

You may want to team up with a local robotic group if you can locate one in your area. This IS NOT a project to cut your teeth on.

Ray

JoeN: No Arduino from any vendor is going to be able to be a mission critical board, at least not without some additional work.

There is a thing called a "Ruggeduino" if you are reasonably paranoid.

JoeN: I have no idea what you mean by buying a full kit. I don't think you are going to find it.

The "starter kits" are unlikely to be useful for this, and rarely represent particularly good economy in any case. Possible a ready-made robot kit if it matches your expectation. Beyond that, you need to determine what you actually need and chase up those parts.

Whereas a Mega may be good for the program memory and RAM, a servo shield using purpose-designed hardware would be more appropriate for 10 servos.

Paul__B: There is a thing called a "Ruggeduino" if you are reasonably paranoid.

I'm aware. I was going to suggest it but the Mega version is not available as the page you link clearly points out and it sounds like he really will need that many outputs if not the memory. Even with the Ruggeduino, I would still totally suggest optoisolation, and if a good job is done isolating it then he probably doesn't need the Ruggeduino anymore anyway except perhaps for bragging rights or "defense in depth". He may not fry a Ruggeduino without good isolation, but I wouldn't be surprised if it still wasn't 100% resistant to restarting with all those motors running. New users tend to freeze/restart their Arduinos with only one motor going half the time.

I'm happy though that I am getting replies instead of the OP as would be more appropriate here. It makes me feel special.

Optoisolation for what? Servos don't need that, they are only supplied a control signal. Motors are controlled via transistor (one direction) or H-bridge (two direction) so the transistor provides the isolation from the Arduino. I believe if the grounding is done well, all going back to one point, being the power supply, a lot of problems are prevented.

JoeN: ... the Mega version is not available as the page you link clearly points out ...

If they have them in October, not much worse than ordering something from China ...

Paul__B:
If they have them in October, not much worse than ordering something from China …

I’d love to have someone order one now and report when it actually comes. I may be a cynic, but I have a boatload of past experience that justifies it. We need a better eye-rolling emote for these circumstances.

I’d say China delivery times are inconsistent rather than bad, though they are usually bad around Christmas and Chinese New Year. I just got this delivered, Nanjing to Chicago and I can’t complain about the delivery speed:

ChinaDelivery.png

JoeN:
<…>
I’d say China delivery times are inconsistent rather than bad, though they are usually bad around Christmas and Chinese New Year.

Every since I switched from eBay to AliExpress, the orders are being delivered on or before the projected date… sometimes, I am surprised by a really fast order until I look and see that it was mailed from a U.S. based “associate.” But, in the past 18 months, absolutely no disappointments due to delivery. An additional plus, no PayPal… just my bank card which manages all of the weird-stuff that used to pass-through PayPal.

Ray

The only problem I have with AliExpress is that for some reason, their checkout system simply does not work!