Electronic devices with compound planetary gearboxes

A head-mounted device, comprising:

• a head-mounted support structure;
• an optical module in the head-mounted support structure;
• and
• an actuator in the head-mounted support structure configured to move the optical module, wherein the actuator comprises:
• a motor;
• and
• a compound planetary gearbox coupled to the motor, comprising:
• an input gear;
• first planet gears having first diameters, wherein the first planet gears are coupled to the input gear;
• second planet gears having second diameters that are less than the first diameters;
• common shafts to which the first planet gears and the second planet gears are coupled;
• and
• a carrier to which the common shafts are coupled, wherein the carrier is configured to rotate to provide output from the compound planetary gearbox.

An electronic device, comprising:

• a housing;
• and
• an actuator in the housing, wherein the actuator comprises:
• a motor;
• a compound planetary gearbox coupled to the motor, wherein the compound planetary gearbox has a reduction ratio of at least 7:1, and the motor and the compound planetary gearbox have a diameter of less than 10 mm and a width of less than 20 mm;
• and
• a lead screw coupled to the compound planetary gearbox.