A surgical assembly for use with and for selective connection to a robotic arm includes an electromechanical instrument and an instrument drive unit. The instrument drive unit includes a motor and a feedback assembly. The motor is configured to effect rotation of the electromechanical instrument. The feedback assembly includes control circuitry and first and second annular members. The control circuitry is configured to sense a change in a condition of the motor. The first annular member has a surface feature projecting therefrom. The second annular member is disposed adjacent the first annular member and has a first surface feature projecting therefrom, circumferentially aligned with the surface feature of the first annular member. Upon a threshold amount of rotation of the first annular member, the surface feature of the first annular member abuts the first surface feature of the second annular member to change the condition of the motor.
