The SparkFun BOB-09322 is a breakout board design to fit a photo transistor GP1A57HRJ00F.
A simple breakout PCB for the GP1A57HR photo interrupter. This PCB has three connections for PWR, GND, and Signal.
When the gate is clear, SIG will be high (>4.9V). When the gate is blocked by a finger, writing utensil, food pellet, or anything else - SIG will go low (<0.4V).
Assembled picture is for reference only, board comes bare; photo interrupter and the 220Ω (330Ω, works as well) current limiting resistor are listed below.
Note: The GP1A57HR has a plastic tab which gets in the way. You can cut it off and it will fit flush in the board.
Schematic design BOB-09322