  In optical experiments, shutters are devices that open or close a path of
light. They are often used to limit the duration of light exposure onto a
target or onto a detector in order to reduce possible light-induced damage.
Many commercial shutters are available for different applications - some
provide very fast opening and closing times, some can handle large optical
powers, and others allow for fail-safe operation. Many of these devices are
costly and offer limited control options. Here we provide an open-source design
for a low-cost, general purpose shutter system based on ubiquitous servo motors
that are connected to an Arduino-based controller. Several shutters can be
controlled by one controller, further reducing system cost. The state of the
shutters can be controlled via a display built into the controller, by serial
commands via USB, or by electrical control lines. The use of a microcontroller
makes the shutter controller adaptable - only control options that are used
need to be included, and the design accommodates a selection of display and
servo options. We provide designs for all required components, including 3D
print files for the servo holders and cases, software for the Arduino,
libraries for serial communication (C and python), and example graphical user
interfaces for testing.
