Hi all I don’t have any experience in robotics but I’m hopeful someone here might give me some guidance. I have made a baseball pitching machine out of an old treadmill. I am using foam softball sized balls and have the actual throwing mechanism finished but need help with making a ball feeding mechanism. The balls will be held in a container above the “throwing wheel” I would like to be able to feed them at a variable rate into a conduit where they will drop onto the throwing wheel. My thought is to maybe have a small wheel that slowly rotates against the upper surface of a ball. This is where as sergeant schultz would say " I know nothing" 
Maybe I could have a small dc motor with a controller that has a dial on it too select the motor speed? I am gleaming from my reading that this might be a relatively simple solution ?
Would anyone have any specific suggestions for a motor and controller? Perhaps there are other simple options ? I can provide more information/description if it is needed. Thanks in advance for any help Rick
Hey Rick,
Welcome to the community!
I have drawn a quick sketch of what I believe you would need.
First of all you will need a small motor with slow RPM. (geared motor)
The best place to find this is here: https://www.robotshop.com/en/gear-motors.html
You will probably also want to add a hub to the shaft of the motor, this will allow you to install all kind of device or mechanical track to the motor: https://www.robotshop.com/en/hubs-couplers.html
Tracks: https://www.robotshop.com/en/gears-belts-pulleys-tracks-sprockets-chains.html
To control the speed of your motor, you can use a transistor with a variable resistor at the base of the power transistor.
The voltage applied to the base of the transistor would control the speed of the motor. This could be done with a potentiometer and a MOSFET.
Or you could also use a DC motor driver: https://www.robotshop.com/en/brushed-motor-controllers.html
I know this can be a lot of information but do not hesitate to ask if you have any more specifics questions and show me any update on your design.
Hi Pjutras First… thanks a lot for the response. I will check those things out.
I was thinking I would post a couple of pics of my project. There is an element that I didn’t put in my original post because I thought i might be complicating things trying to incorporate it. It involves using a gear reduction mechanism that I have.
this pic shows the gear reduction sitting beside the pipe where the balls will drop. I was thinking of cutting a slot in the interior radius of the conduit so the rotating rubber sleeve protrudes to the inside of the conduit and comes in contact with the upper surface of the ball. I put a drill on the gear reducer and took this video as the ball is moved forward. It takes about 15 seconds to move the ball forward
https://1drv.ms/v/s!AmFt3IOfS6hkkkJhJjoyfvySR4EL
i think the rpm of the drill is approx 1500… maybe i need a motor that will drive the reducer?
maybe 500 to 2000 rpm ? Im just guessing here thanks in advance if you have any thoughts or suggestions
I am having a bit of trouble trying to pick out a motor and controller combination. I guess I just don’t understand the best route to take here. If I proceed without using the gear reduction unit I have above I would need some small motor/controller combination capable of a variable slow rpm range of somewhere between 2 to 8 or so rpm.
If I use the gear reduction above I would need a variable speed motor/controller combination capable of say 1000 to 2000 rpm output. Again its the marrying of the motor controller combination that I don’t seem to be able to figure out. If someone had a specific suggestion on this it would be much appreciated. Thanks in advance Rick
Sorry for the delay.
You would be best using a DC geared motor that output around 2-6 RPM.
The torque will be pretty high and than you can use a single DC motor driver for the control.
thanks I was thinking of using this motor
…would you be open to suggesting a dc driver that I could purchase with this motor that would allow me to vary the speed down to say 1 or 2 rpm? I looked at the controllers you linked to previously but didnt see any with a rotary dial or slider that could be used to change the speed. Thanks much for contributing …its much appreciated Rick
This might suit your need. Please check it out
you know yuan this looks perfect… thanks alot i will get these ordered again thanks to both you guys for the help