This machine lets you practice baseball solo, similar to Topgolf

Topgolf has a pretty brilliant business model: let golfers do the fun stuff (driving balls at max power), without any of the complications, time commitments, or logistics of running through a full 18-hole course. Batting cages exist to do something similar for baseball, but Pete LeMaster didn’t want to practice batting — he wanted to practice catching and throwing. That’s why he built this baseball machine called The Fielder’s Choice.

The Fielder’s Choice is a machine that can automatically shoot a ball at any horizontal and vertical angle within a baseball diamond from home plate, for the user to catch. They can then throw the ball back to the machine, which will “catch it” and then shoot it again. That process repeats until the user can’t move their arm anymore — though there is also a mode to gamify the practice sessions, which is more motivating.

To avoid reinventing the wheel (literally), LeMaster started with a pitching machine that feeds balls down a ramp to a wheel spinning at high speed, which then flings the ball. To introduce some variability, LeMaster added pan and tilt motors. A linear actuator does the tilting, while a stepper motor and 3D-printed gearset do the panning. Two proximity sensors act as limit switches for the pan mechanism.

“Catching” returned balls was a bit more complicated and LeMaster achieved that with a net that feeds down into a flexible tube routed to the input of the pitching machine. A proximity sensor and servo-actuated arm prevent balls from dropping into the machine until it is ready for a pitch.

To control those functions, LeMaster used Arduino’s Opta line of micro PLCs An Opta PLC WiFi with an Opta Digital Expansion D1608E module reads the proximity sensor inputs, then controls some of the outputs directly, including the relay that sends power to the pitching machine’s drive motor. Other outputs, like the PWM single for the stepper motor driver, go through an Arduino Nano board, which can maintain timing separately from the primary logic. An interface running on a connected laptop lets the user configure the parameters of games, like the number of balls to pitch.

It all seems to work very well and as long as the user can throw the ball into the net, they can keep practicing indefinitely.