Micro Servo with Position Feedback
The FS90-FB is a specially modified version of FEETECH’s FS90 micro 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.
Like the FS90, the FS90-FB works with standard RC servo pulses, providing a running angle of approximately 120° over a servo pulse range of 900 µs to 2100 µs. As with most servos, the pulse range can be expanded to achieve an expanded operating angle, but the limits of this are not specified by FEETECH. The feedback voltage varies linearly over this range, and there is approximately a 1:1 correspondence between the feedback in millivolts and the servo position in milliseconds. For example, the feedback voltage will be around 1.5 V when the servo output is at the position corresponding to 1.5 ms.
The servo signal, power, and ground are provided through an extra-long 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 15″ (38 cm) long (which is almost twice as long as the cables on the standard FS90).