Developed high torque stepper motors in the world's smallest size !

Oct. 2, 2006

Stepper Motor SM3.7-20 series
Stepper Motor SM3.7-20 series

FDK Corporation has developed the world's smallest stepper (stepping) motors, the SM3.7 series. The motors will be exhibited at CEATEC JAPAN 2006 (Booth no. 6E104) to be held from October 3-7, 2006.

Although these stepper motors are only 3.7mm in diameter, they turn a full circle in 20 steps. Compared with the SM4.3 series developed in June, 2005, which were the smallest stepper motors at that time, the new series of motors are 30% lighter in weight, just 0.27 grams) and 25% smaller in area (3.7mm diameter × 5.1mm in length). Regarding pull-in torque, the permanent magnets we developed for this series have the maximum constant torque for a synchronous motor and succeed in minimizing torque loss even though the motor size has been reduced.

FDK's new SM3.7-20 stepper motor series enables manufacturers to reduce the size, weight and power consumption of electrical and electronic equipment. The series complies with the RoHS Directive, which is the EU's directive on the restriction of hazardous substances in electrical and electronic equipment.
This space-saving high torque SM3.7 series is expected to be adopted for mobile phones and any other devices such as optical pick-ups of Blu-ray discs (next generation DVDs) as the demand continues for these products to be downsized and there is a requirement for precise measuring of a motor's rotor position.

*1 The world's smallest size in diameter (researched by FDK)

For more information visit our website at

Product name Stepper Motor SM3.7-20 series
Dimensions (mm) 3.7 (diameter.) × 5.1 (length)
Shaft diameter (mm) 0.6
Weight (g) 0.27
No. of steps (step angle) 20 (1 step angle=18)
Coil resistance 22 ohm/phase
Voltage between terminals 3V
Pull-in torque 0.045mN.m (2 phase.500pps hour)

Contacts: FDK Corporation
Corporate Communication Office


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