An ultrasonic surgical device comprises a handle assembly, a shaft assembly, and a removable transducer module. The transducer module includes a waveguide, a locking mechanism, and an electronics assembly including at least one button. The handle assembly includes a trigger assembly configured to actuate the button(s) of the electronics assembly when the transducer module is coupled with the handle assembly. The shaft assembly engages the waveguide of the transducer module and is disposed at the distal end of the handle assembly. The distal end of the shaft assembly includes a harmonic blade. When assembled with the handle assembly, the transducer module is capable of providing ultrasonic energy to the harmonic blade.