An example injector includes a rotary knob for selecting a function and setting a dosing quantity for an injection, a button located on an end of the rotary knob for initiating the injection, an electric motor, an encoder for evaluating output rotary motion of the motor, and a processor that converts the dosing quantity into a number of encoder pulses and controls operation of the motor based on the number of encoder pulses when dosage is triggered. The injector also includes a transmission coupled to the electric motor to convert a speed of the motor, a threaded spindle coupled to the transmission that moves linearly based on the output rotary motion of the motor at the speed as converted by the transmission, and a punch connected to an end of the threaded spindle. The linear movement of the spindle causes the punch to release medicament.