View Full Version : Help on choosing parts

08-11-2009, 11:31 PM
Hi Adrenalynn,

I'm addressing you directly because you are exceptional.

I'll describe my project before asking my questions.
I'm trying to build a remote controlled ball to serve as a toy for my cat! :)
The ball is a 5 inch diameter plastic ball weighing 2.95 oz.
The ball is 2 cm thick.
The design is a simple one; one actuated wheel (1.26 inches diameter) will use two gear motors for two degrees of freedom; one motor for yaw and one motor for pitch. Another identical wheel (but unactuated) is used as a stabilizer. This is how control of ball direction and speed is accomplished.
The drive mechansim from top to bottom is (crudely) depicted below.
O <--Unactuated wheel rolling against one side of the ball.
= <--Spring for suspension
NN <--Plate that holds 2 channel reciever, batteries (and microcontroller??)
M <--Geared motor to actuate bottom wheel for yaw (to change direction of ball roll)
OM <--Actuated wheel (to change speed) with gear motor for pitch rolling on opposite side of ball with respect to the unactuated wheel.
There is a backbone to attach all parts that isn't depicted above.
The drive mechanism will fit inside the ball.
Do I really need a microcontroller for this or will a remote control transmitter/receiver setup be enough to control two motors to rotate the the bottom drive wheel in the yaw and pitch directions?

Do you believe I can get all the necessary parts small enough to fit in the ball?
Do you recommend any specific parts/brands based on your experience? (RC Transmitter/receiver?/Wheels/batteries/etc.)

I hope all is going well for you.
Your advice is cherished,

Thank you,


08-12-2009, 08:49 PM
There used to be an RC toy ball that I really wanted. It had a pole mounted through the center line, and a motor with a weight attached to it...probably the battery mounted below the pole. The motor ran in reverse which moved the weight out of the center of gravity causing the ball to roll. The weight was mounted on a servo so it could move from side to side when the ball was supposed to change direction. I think it was sold by sharper image.

There is also this:


08-13-2009, 08:17 PM
Hi Sam,

Lots of smart people here!

Sure, you could do it with an R/C setup. You'll need some kind of motor controller though. Maybe a little sabertooth?

I'm partial to the HiTec stuff for bang-for-buck. If you want a new 2.4, then look elsewhere, but if you want just straight up cheap working forever - HiTec is the way to go. Make sure you get ground (75Mhz) frequency rather than Aircraft!

But, yeah, motor controller, R/C receiver, motors. Sounds you have your mechanics figured out. You'll need at least 6v worth of battery, preferably 7.2v. That will be the only problem that I see - swinging the battery weight around.