Bottom view of FEETECH FS90R micro continuous rotation servo (V2.0) showing middle-point adjustment potentiometer.

Overview

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; just throw on a pair of wheels and your robot is ready to roll!

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.

The servo has a 10″ (250 mm) lead that is terminated with a JR-style connector and includes additional servo horns and mounting hardware. The following picture shows an example of the hardware that might be included (actual hardware could vary):

This robotics servo, which is a continuous rotation version of the FEETECH FS90, is compatible with our servo controllers. If you are looking for a similar servo that is capable of limited-range position control as opposed to continuous rotation speed control, consider the FS90, which has identical dimensions and uses the same motor, or the Power HD micro servo HD-1900A, which has almost the same weight, speed, and torque as the FS90.

Note that, as with most hobby servos, stalling or back-driving this servo can damage it.

Wheels

If you want to use this servo as an actuator for your miniature robot, you will need a wheel to go with it. Fortunately, we carry compatible servo wheels for micro servos (21T, 4.8 mm spline):

60 mm and 40 mm Pololu Wheels for Micro Servo Splines on FEETECH’s FT90R and FS90R micro continuous rotation servos.

The 60×8mm wheel allows for a top speed of around 42 cm/s (1.3 ft/s) at 6 V.

Continuous rotation servo comparison

Continuous rotation servo size comparison. From left to right: SpringRC SM-S4303R, Power HD AR-3606HB, FEETECH FS5106R, Parallax Feedback 360°, Parallax (Futaba S148), and FEETECH FS90R.

	6 V		4.8 V		Weight (g)	Size (mm)	Direction vs pulse (1ms → 2ms)	Digital?	Feed­back?	Price
	Max speed (RPM)	Stall torque (oz·in)	Max speed (RPM)	Stall torque (oz·in)
SpringRC SM-S4303R	54	71	43	46	41	41.3 × 20.7 × 40.2	CW→CCW			$14.95
SURPLUS SpringRC SM-S4303R 2-Pack	54	71	43	46	41	41.3 × 20.7 × 40.2	CCW→CW			$19.95 for a pair of servos
FEETECH FS5106R	95	83	75	67	43	40.8 × 20.1 × 38.0	CW→CCW			$15.95
Parallax Feedback 360°	140	35	–	–	41	40.0 × 20.0 × 37.2	CW→CCW			$27.99
FEETECH FT90R	135	21	108	18	9	22.9 × 12.1 × 26.5	CW→CCW			$8.95
FEETECH FS90R	130	21	100	18	9	22.5 × 12.1 × 23.4	CW→CCW			$5.95

People often buy this product together with:

Micro Maestro 6-Channel USB Servo Controller (Assembled)