Motor selection for tennis ball launcher

Other Hardware Motors, Mechanics, Power and CNC
1

Hi, I'm new to the world of arduino/coding and have some questions regarding motor selection and power.

The project that I started with is creating a tennis ball launcher that my dog can use on her own. I had bought an Elegoo Smart Car Kit, built it quickly and didn't do much with it so I wanted to repurpose those parts. So I'm currently working with an Arduino Uno with an expansion board that has a TB6612FNG motor driver, a TT DC motor, and a 7.4V lithium battery pack.

I had a feeling that the motor wouldn't be powerful enough for this application, so I made a test prototype to check (for other project reasons, I can only use 1 motor to drive both wheels).

image
image743×991 73.6 KB

Sure enough, the ball either comes out very slowly or jams the motor. So my questions are:

  1. What motor spec should I be paying most attention to for selecting a new motor? Voltage? Current? Both??

  2. If I understand correctly, my delivery to the motor is limited by the driver and power supply. The driver can output 15V, 1.2A average / 3.2A peak. So I guess I'm currently limited by the 7.4V battery pack?

  3. Since the driver has a max output voltage of 15V, would there be no point in getting a DC motor with higher voltage capacity?

  4. Would I have to wire this externally instead of connecting to the arduino expansion board?

Thanks for any and all help!

1 Like
2

Maybe something that uses a spinning wheel or compressed air?
Or swings a weight on an arm that takes seconds to raise?

1 Like
3

Your problem is not the motor, but the inertia of the whole design. Mix up some redimix concrete and fill the wheels to give some weight to the wheels! Then try it again. Will take a bit of time to spin up the wheels.

1 Like
4

Great idea, I'll try that first - thanks! Also I'll add here for clarity that by "launcher" I really mean just a quick roll across the floor since this will be indoors.

5

I like the swinging arm since this will just roll across the floor - might resort to that if I can't get things working :slight_smile:

6

At industrial scale, our turret punch used a flywheel with electric clutch,

on a smaller scale, use a pump to compress a few liters of air not greatly to do what a beer can mortar uses lighter fluid or hair spray to launch tennis balls wayyyy too hard for your use -- a tennis ball fits a standard soda or beer can near exactly.

7

Push the ball into a downwards directed plane. When launch time, release time, comes push a ball onto the plane and let gravity give the ball its speed.

8

A quick roll? Long ago Dad told us that our dog took the ball up the stairs and threw it down to chase when we boys were in school.

Air time adds excitement!

For your needs... a DC motor with a cam is all you need to kick that ball!. It will build momentum just bringing the high spot around.

Or kick a linear solenoid. Lots of Watts for a very short burst, a small bank of capacitors can do that!

PS -- getting the dog to reload the thing and then triggering it might be the hard part!

1 Like
9

Have a look at how the ones you can buy work

2 Likes
10

Hahaha our dog does that at other peoples' houses, but our apartment unfortunately doesn't have any stairs.

Spent some time last night reading through other peoples' ball launcher project questions and came to the same conclusion about the cam - that might be the direction I go in.

And yeah, training is definitely going to be the hard part unfortunately, but I'm hoping her love of tennis balls motivates her

image
image659×879 134 KB

11

Did just this and most operate with two motors and flywheels. Might buy a nerf ball launcher to disassemble too - for science, of course

12

Once she sees it as a toy, what you do should get copied.. when you don't make it go!

13

Lots on tube Here !

14

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.