Play Ball!

Baseball didn’t come to be known as America's national pastime for nothing. People love everything about baseball, from the crack of the bat to the smell of hot dogs and fresh-cut grass in the summertime. And as a team game, playing a few innings of baseball is a great way to get out and socialize with friends. But if you want to get out on the diamond for a little practice on your own — well, let’s just say that trying to throw the ball to yourself doesn’t work out so well.

But that’s nothing that can’t be solved with technology, says YouTuber Pete LeMaster. He wanted to build a machine that could turn a solo baseball outing into a Topgolf-like experience. To make that happen, he designed and built what he calls the Fielder's Choice. It may not be much to look at, with its rough wooden frame and cobbled together components, but it does a great job of not only playing catch, but also gamifying the experience.

The main functions of the Fielder's Choice are to catch and throw a baseball. Catching is relatively easy; LeMaster picked up a second-hand batting practice net to make catches. A stretch of dryer vent hose was attached to an opening at the bottom of the netting to guide the ball into the throwing mechanism.

As far as the throwing mechanism is concerned, it is built around a commercial pitching machine. But LeMaster wanted to be able to control when the ball is thrown, so a custom, 3D-printed enclosure was attached between the hose and the intake of the pitching machine. A gate in this enclosure, which is controlled by a servo, holds the ball in place until a signal is sent telling it to throw the ball. An infrared proximity sensor lets the system know when a ball is in place and ready to throw.

Throwing the same pitch time and again wouldn’t be very much fun, so a linear actuator was attached to the base of the Fielder's Choice to control its elevation. A stepper motor and set of gears were also attached to a pole, on top of which the pitching machine is located, to allow for rotational adjustments.

An Arduino Opta micro PLC handles supplying each of the components with the proper voltage, and turning them on and off as needed. An Arduino Nano was also included in the build to generate PWM signals to control the servos.

To complete the build, LeMaster programmed the Fielder's Choice to play three user-selectable games. The first is just an infinite game of catch. Another game, called “around the horn,” will get the player running all around the infield as it launches a mix of line drives and grounders between first and third base. The final game, called “field your position,” will throw a variety of pitches to a particular spot in the infield for those that want to work on their position-specific skills.

The Fielder's Choice may sound like a complicated build, but the individual components that make it up are relatively simple. If you get started now, you could easily have your own robotic baseball buddy ready before next spring rolls around.