Feetech SM40BL 12V 40kg.cm RS485 Serial Bus Brushless Servo

The Feetech SM40BL is a 12 V smart servo that pairs a brushless motor with a steel gearbox in an aluminium alloy case, controlled over an RS485 serial bus. Use it for robotic arms, positioning systems and robot joints that need 40 kg.cm of stall torque with 4096-step position control across 360°.

Key features

• 40 kg.cm peak stall and 12 kg.cm rated torque at 12 V, drawing 2.5 A at stall

• 0.153 s/60° (65 RPM) no-load speed

• RS485 half-duplex bus with IDs 0–253, so many servos share one cable run

• Reports load, position, speed, input voltage and temperature

• Aluminium horn on a 25T 5.96 mm spline, two ball bearings

Specifications

• Operating voltage: 12 V

• Stall torque: 40 kg.cm at 12 V

• Rated torque: 12 kg.cm at 12 V

• Stall current: 2.5 A at 12 V

• No-load current: 200 mA

• No-load speed: 0.153 s/60° (65 RPM)

• Position range: 360° (0–4095)

• Control: RS485 bus, half-duplex asynchronous serial

• Motor: brushless

• Horn spline: 25T, 5.96 mm

• Dimensions: 46.5 × 28.5 × 34 mm

• Lead length: 150 mm

• Weight: 100 g

• Operating temperature: -15 to 70 °C

RS485 is a differential bus suited to longer cable runs and electrically noisy machines. You need an RS485 servo controller or USB-RS485 adapter; a PWM receiver or TTL bus board will not drive it.