Quote:
Originally Posted by msimon785
Can I suggest that instead of spending upwards of $65 (that seems to be a minimum for motor controllers, you build an H-Bridge. They're a simple, intuitive, and fairly cheap
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the darlington transistor
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The problem with these methods is simply the amount of current that the controller needs to handle. Most of the pages you'll find on the Internet describing these circuits are targeting small ~3-5W "hobby motors," whereas something like the RS-550 will pull hundreds of Watts at stall (the specs cite a 85A stall current) (hopefully you'll never get there if you just want a robot "that you can experiment with) and even unloaded, they'll pull 30W.
It is possible to build your own controller that can handle these kinds of loads (the
Open Source Motor Controller project comes to mind), but as squirrel says, you may end up spending as much on parts if you're only building a couple, and this depends on much you trust your electronics skills (nasty things happen when that much current goes places it shouldn't). It would be a fantastic learning experience, but I would suggest tracking down an electronics mentor from your friendly neighborhood robotics team to help you with the project.
If you're more interested in the programming side of things, it's probably easier to buy a pre-built motor controller if you're looking to use motors that powerful. Something you may ask yourself is what the objective of your project is, and if you actually need that powerful of a motor. Honestly, you'll be pretty hard pressed to find a better price than $60 for a motor controller that can handle 45A. If you're concerned about dropping $60 on a motor controller, keep in mind that you're spending that much for each of the gearboxes as well.
Unfortunately, building robots can be an expensive hobby...
Speaking from experience, the more difficult exercise than assembling your control system is designing and fabricating a chassis to hold the parts. Your robotics team may be able to help you with this, but, again, it depends on how much you're interested in the design and construction versus the programming. Again, evaluate what your objectives are for the project. Something to look into may be some of the
kits available that specifically target Arduinos as control systems.
--Ryan