Aspects of the present disclosure are presented for a circuit design that provides automatic ultrasonic energy activation for a modular surgical system. In some aspects, a control circuit in an ultrasonic surgical instrument may be connected to a modular energy system that allows therapeutic energy to pass from a generator to the ultrasonic surgical instrument after automatically activating the ultrasonic functionality based on some threshold criterion being satisfied. In some aspects, the ultrasonic instrument may include a capacitive touch sensor that sends a signal to automatically activate the therapeutic ultrasonic energy when the touch sensor contacts appropriate tissue.
