Photodiode and Arduino to measure the speed of a projectile
You need to determine if you want your detector to operate in photovoltaic or photoconductive mode. If the former, simply get rid of R1 and reverse your PD.







simulate this circuit &ndash; Schematic created using CircuitLab

If the latter, reverse the postion of R1 and the PD, like so







simulate this circuit

In theory, photoconductive is faster than photovoltaic, since the 5 volts will act as a bias voltage on the PD, reducing the PD capacitance. However, the large 1M combined with op amp input capacitance acts as a low-pass filter, and with no capacitance figure on the op amp data sheet, and no data sheet for the PD, I have no idea which effect will dominate.