And another question, how do I know how much torque I will need for my tracked robot which weighs around 20KG or less? Is the motor located in the link I provided a bit of an overkill for such robot?
At 900+ rpm, you are going to have one quick tracked bot. Below are two h-bridges that might fit your needs.http://www.parallax.com/tabid/768/ProductID/64/Default.aspxhttp://secure.oatleyelectronics.com//product_info.php?products_id=206&osCsid=30093449b694ae247d94c2bcce5d0560
I think there are a number of options on the site that sells the motor $) - have you looked through these? Maybe:http://www.robotmarketplace.com/products/RS-RS160D.html
There isn't going to be any cheap and easy options when dealing with motors with such high stall currents. The site you're getting the motor from does provide a number of speed controllers that operate at those currents and higher, but they start getting pricey. Building a large robot is a pricey endeavor though, no way around that really unless you can hand build virtually every component of the robot, and then you're really just trading financial cost for time cost.As for the appropriate size motor for your robot, that depends on a variety of factors. How fast you want the robot to go. What kind of tire setup you are using. Treaded setups require a lot of torque for differential steering as you are doing a lot of skidding and need to be able to overcome the static friction between the treads and the ground, and even this friction will vary from surface to surface. For the same reason 4 wheels differential steer system will require more torque than 2 wheel setups. 6, 8, and more wheels will all require more torque as well.
Quote from: amanmazleifg on May 31, 2011, 11:54 amAnd another question, how do I know how much torque I will need for my tracked robot which weighs around 20KG or less? Is the motor located in the link I provided a bit of an overkill for such robot?Two questions you need to answer:1) What is the radius of your drive wheels?2) If you tied a rope to your robot and pulled on it, how much force would you need to apply before the robot lost traction and started sliding? Using a hypothetical answer of 10kg of force to slide the robot and wheels of 5 cm radius, then you'd need a motor with 10kg * 5cm = 50kg/cm of torque.
I agree with everything that Aeturnalus said. Furthermore, that stall current value is very questionable. In other forums, people are doubtful of that number. I think that it would be a good idea to measure the stall torque yourself. The method is to simply connect the motor to a power supply with a current meter in the line, and grab the shaft and stall (or attempt to stall) the motor. Of course you would only do this momentarily (for a second or two) to see what the maximum current is.
so what do you guys propose that I do?