FEETECH High-Torque Servo FS5115M-FB with Position Feedback

This version of the FS5115M high-torque servo from FEETECH is specially modified to provide access to the feedback potentiometer through a fourth (green) wire, allowing you to directly measure the position of the output. This extra information enables more complex robotics applications, such as determining when the servo has reached its target, detecting when the output is blocked, or implementing your own higher-level closed-loop position control.

Key specs at 6 V: 0.16 sec/60°, 215 oz-in (15.5 kg-cm), 60 g.

Overview

The FS5115M-FB is a specially modified version of FEETECH’s FS5115M standard-size high-torque analog servo that provides access to the feedback potentiometer through a fourth (green) wire, which makes it possible to directly measure the output angle. With this extra information, you can determine when the servo has reached its target position (or detect if something is interfering with its ability to get there). This feedback also enables more complex closed-loop control of the servo from your main controller.

The FS5115M-FB is a standard-size analog servo from FEETECH that can deliver more than twice the torque of our standard-size servos with plastic gears thanks to its powerful motor and all-metal gear train (if you need even more torque than this, check out the larger FT5335M giant servo). The output shaft is supported by two ball bearings for reduced friction.

Like the FS5115M, the FS5115M-FB works with standard RC servo pulses, providing a running angle of approximately 180° over a servo pulse range of 500 µs to 2500 µs. The feedback voltage varies linearly over this range by a couple of volts.

The servo signal, power, and ground are provided through a 3-wire servo cable that is terminated with a standard JR-style connector, which is Futaba-compatible. The feedback is accessible through a separate green wire that is terminated like our female premium jumper wires and works with standard 0.1″ male header pins. These cables are approximately 12″ (30 cm) long.

Servo and feedback connectors on the FEETECH servos with position feedback.

For more information about this servo, see the FS5115M datasheet (133k pdf) (please note that this is the datasheet for the standard FS5115M, so it does not include any information about the special feedback modification).

FEETECH High-Torque Servo FS5115M with included hardware (actual hardware might vary).

This servo is also compatible with our Mounting Bracket for Standard-Size Servos:

The picture below shows the all-metal gear train that helps the servo deliver such high torque:

Note that, as with most hobby servos, stalling or back-driving this servo can damage it. This servo can draw bursts of current in excess of 3 A at 6 V, so please make sure you have an appropriate power supply. For comparison, a typical standard-size servo might draw around an amp when straining.

Comparison to the Power HD 1501MG servo

The FS5115M is a lower-cost alternative to the 1501MG from Power HD, which has nearly identical dimensions and similar performance. The two servos should be generally interchangeable for most applications. The picture below shows both the FS5115M and the 1501MG side by side: