[RyanCahoon]

Originally Posted by smartkid

To what RyanCahoon said, "you're probably going to want motors along the lines of what's used in FIRST [...] a lot of the low-current motor controllers would fizzle and die" Yes, the computer power supply uses 12V and 5V leads so the car battery we hope to use for power later on and the motors will all be 12V.

The design calls for 4 12V DC motors to move the bot in an omni wheel system

...

The question that comes to mind though is do I really need to buy 4 $100+ speed controllers? I've worked on our teams FRC bot, what we're hoping to do is about 1.5 times smaller then that and shouldn't need quite as powerful motors.

Originally Posted by dtengineering

There are a number of sub-$100 options. You could check out www.robotshop.ca or a number of other on-line robotics suppliers for options. Or you could take a look at building your own. Here are some links that might help, the first one is truly worth checking out:

http://www.mcmanis.com/chuck/Robotics/
http://www.barello.net/Papers/H-Bridge.pdf
http://www.armory.com/~rstevew/Publi...d/h-bridge.htm

There is also an online collaboration to create an "open source motor controller", or try googling robotics clubs such as the Seattle Robotics Society. They have some excellent information and links on their web site.

The general answer is you need to check the amp draw on your motors and compare it to the max current rating of the motor controller you're considering. I was just warning against using something like this to power a decent sized motor. I pointed out the Victors because you'd be hard pressed to find a 40 Amp controller for a better price. If your motors are less, than feel free to use a less expensive controller. I looked at the robotshop.ca page Jason referred to, and there are several 25A controllers for under $100, but you'll still be paying at least $75 per unit. I haven't looked at the open source controlleres; you may be able to get the price down if you build one yourself.

On the topic of USB vs. Serial: On the PC end of things, USB really depends on how the device is set up. I noticed on the Pololu board that they're basically running a little USB-Serial module and it just looks like another serial port on the computer anyway. The one advantage to using USB over pure serial is USB is, of course, more modern and (in my experience) is less finicky with connection settings - no baud rate, stop bits, parity, etc to deal with.

Hope I've helped some instead of just muddying the waters.

--Ryan