The FS90R is a micro-sized servo that has been built by FEETECH (formerly known as Fitec) specifically for continuous rotation.
At 6 V, it has a maximum rotation speed of around 130 RPM (no-load) and can produce up to 21 oz-in (1.5 kg-cm) of torque.
The servo can be controlled using a direct connection to a single microcontroller I/O line without any additional electronics,
which makes it a great miniature actuator for beginner robotics projects.
The FS90R continuous rotation servo converts standard RC servo position pulses into continuous rotation speed.
The default rest point is 1.5 ms, but this can be adjusted by using a small screwdriver to turn the middle-point adjustment potentiometer.
Pulse widths above the rest point result in counterclockwise rotation, with speed increasing as the pulse width increases;
pulse widths below the rest point result in clockwise rotation, with speed increasing as the pulse width decreases.