Continuous Rotation Servos, Stepper Motors, Gearmotors, StepperMotor Drivers

Hey there everyone,

I’m new to this sub and excited to be here! I’ve been a hobbyist for a while now but I never delved too deep into the whole motor game- I usually could rely on simple singular servo controls. Feel free to tell me I’m an idiot, I already suspect it.

Now, I’m trying to get two continuously rotating servos to sync up. Essentially what I have is a ball sitting on a hole cut out of some acrylic, and the two servos sitting just under the ball so that the wheels, which I’ve lined with rubber bands for grip, can push the ball from under it, making it spin in place. I want to be able to rotate it up, down, left, and right. This means that the servos need to be in sync when spinning in the same direction, or in opposite directions. If they spin at different speeds at all, the ball starts rotating in ways I can’t predict or control.

How can I make these two servos sync up? I’ve looked at stepper motors, but I suspect they’re not necessary for my needs, as I don’t need to know position- just speed. I understand they can control that better as well, but I’m just skeptical that I need it. I’m looking at stepper motor drivers which I can see could be used on continuously rotating servos, but I’m still not totally certain of what they even do. Fine tune control? Do they make sure two servos sync up? I don’t think so.

I received some advice from a hobby shop that a y-harness jumper would do the trick, and when I mentioned the servos spinning in opposite directions as well, he mentioned something about an aileron, which just completely confused me.
Can anyone help me grasp this concept a bit more clearly? I can do all the googling in the world for days but some things are just easier to understand through dialogue.

Thanks everyone

I don't think it would be possible to make any two DC motors (which is what a continuous servo is) move at the exact same speed without the ability to measure the speed and adjust it automatically. That is certainly possible with an Arduino but if extremely close co-ordination of the movement and speeds is required it will be complex.

Standard servos are designed to provide position control (for example ailerons on model aircraft) and it is certainly possible to sync the position and to have servos move to opposing positions. But continuous servos don't have that sort of control. And for regular servos the speed is usually irrelevant as long as they are sufficiently responsive.

The speed of a stepper motor is determined by the time interval between step pulses so it is easy to control. But stepper motors don't move smoothly like a DC motor. Microstepping can greatly reduce the jerkiness but it won't eliminate it.

Every motor needs a motor driver between it and the Arduino. In the case of servos the driver is inside the package.

Have a look at these links for extra background info Stepper Motor Basics Simple Stepper Code