I would appreciate if I could get some recommendations on the selection of motors and batteries for use with the Arduino Uno R3 & Arduino Motor Shield R3. We are attempting to build an autonomous robot to play a soccer game.
Scale: The scale of the robot is weight 2.4 KG max and about 8 inches round, 8 inches high. We will be using 2 drive motors.
I understand that in general that we can independently drive two motors with a voltage rating of 5-12 volts, and amperage of 2 amp each motor max.
Can someone recommend some motors that would be suitable for this small scale project? Hopefully motors that you have some past experience and know would work well in this project.
Any recommendations on batteries would also be appreciated.
The most important thing to look at when selecting a motor is the stall current vs the current that your motor driver can handle. Some motor drivers say they can handle 2A when but can only do so for a short amount of time without cooling. I tend to be cautious and buy a controller that can handle a sustained stall current, just in case the robot gets stuck. Pololu has a variety of motor controllers that would be appropriate. You can also build your own h-bridges for a cheaper option.
For batteries, I would recommend either LiPo or Nimh. LiPo can provide more power and has a higher energy density (will run longer) but also requires careful charging and monitoring. Nihm are easier to work with but not as powerful. Whatever battery you use, I would suggest separating your logic circuits from you motor power. Back emf from the motors spinning can cause interference with the other electronics. Also I've seen so many people burn out arduino boards because they see a motor rated at 5V and think they can power it off of one of the pins.
Its unwise to start with a motor driver board and a set of mechanical requirements - the
latter determine the size of motor which in turns determines the requirements on the
motor driver.
There are many factors to consider, but from the mechanical side you need figure out
the speed, torque and power you want - this will help select the right power of motor
and gear ratios. Then look for (gear)motors of that sort of rating, allowing a generous
safety margin (have you considered acceleration loads, friction, etc?).
The Arduino motor shield can't source very much current at all (1A is really pushing it,
the advertised 2A isn't attainable without adding heatsinks and forced air cooling with
the L298 chip.
I'd suggest you go for higher voltage supply, 12V or even 18 or 24, since
the L298 is more effcicient which higher voltages and you'll get to be able to control
more power with limited current. (Remembler the L298 can waste 2.5V to 4V)
That weight would allow for small SLA 12V battery or NiMH's or a 3S LiPo (11.1V).
Of course the latter would allow lighter weight and reduce demands on propulsion
system.
Choice of motors for small robots is rather bound up with choice of wheel as there are
a variety of wheel+gearmotor assemblies available at reasonable cost around.
Do you have any idea what maximum speed, maximum acceleration and wheel size
are ?