DFRobot
DFRobot ST3215 12V Serial Bus Servo - 30kg.cm, 360° Encoder
· MPN: SER0070
The ST3215 is an intelligent serial bus servo for robotics and automation projects that need strong torque, position feedback and tidy wiring. It runs from a...
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The ST3215 is an intelligent serial bus servo for robotics and automation projects that need strong torque, position feedback and tidy wiring. It runs from a rated 12V supply and delivers 30kg.cm stall torque through a coreless motor and metal gear train.
A 12-bit magnetic encoder provides 360° absolute position feedback, with 4096 steps and 0.088° resolution. Because it uses non-contact sensing rather than a traditional potentiometer, it is designed for longer service life and repeatable positioning.
Control is via a TTL-level, half-duplex UART serial bus, allowing up to 253 servos to be daisy-chained from a single port. The bus also returns real-time feedback including position, speed, load, voltage and temperature, which is useful for closed-loop robotic systems.
In the box you get the ST3215 Serial Bus Servo-12V 30kg 360° ×1, a servo horn screw accessory kit ×1 and a 3-pin servo cable ×1. A 2D dimension document is also provided by the supplier.
Features:
- 360° high-precision magnetic encoder: 12-bit absolute position feedback over a full 360° range.
- 4096-step resolution: Control accuracy of 0.088°.
- Non-contact sensing: Eliminates physical wear compared with traditional potentiometers.
- One-click midpoint calibration: Set any position within the 360° range as the new centre point.
- High torque: 30kg.cm stall torque for demanding loads.
- Durable gear design: 1:345 gear train constructed from copper and aluminium.
- Robust housing: PA+GF casing for reliability and longevity.
- Angle Servo Mode: Precise 0-360° absolute positioning with configurable acceleration and deceleration.
- Speed Closed-loop Motor Mode: Functions as a DC motor while maintaining constant speed under changing load.
- Speed Open-loop Motor Mode: Functions as a standard DC motor where speed is proportional to voltage and decreases under load.
- Stepping Mode: Incremental motion from the current position with continuous rotation support.
- TTL-level UART serial bus: Half-duplex protocol for simplified multi-servo wiring.
- Daisy-chain support: Up to 253 servos on a single port.
- Bi-directional communication: Real-time feedback for position, speed, load, voltage and temperature.
- Configurable acceleration start/stop: Smoother motion profile with reduced mechanical shock.
- Electronic protections: Built-in overload, overcurrent, overvoltage and overheating protection.
Specifications:
- Rated working voltage: 12V
- No-load speed: 0.222s/60° (45RPM)
- No-load current: 180mA
- Stall torque: 30kg.cm/417.35oz.in
- Stall current: 2.7A
- Standby current: 30mA
- Operating voltage: 4-14V
- Rated load: 10kg.cm
- Rated current: 900mA
- Motor resistance: 1Ω
- Torque constant (Kt): 11kg.cm/A
- Dimensions: 45.2×24.7×35mm
- Housing: PA+GF
- Gear material: Copper
- Bearing: Ball bearing
- Sensor: 12-bit magnetic encoder
- Rotation: 360°
- Connector: 3-pin (Black-GND, Red-VCC, Blue-Signal/TTL)
- Cable length: 15cm
- Weight: 55±1g
- Output shaft: 25T/OD5.9mm
- Gear ratio: 1:345
- Gear backlash: ≤0.5°
- Output shaft screw: M3×6
- Motor type: Coreless
- Signal: Digital
- Protocol: Half-duplex UART (8-bit, 1 stop bit, no parity)
- ID range: 0-253
- Baud rate: 38.4kbps-1Mbps (default: 1Mbps)
- Control algorithm: PID
- Midpoint: 180° (2048 steps)
- Resolution: 0.088°
- Rotation direction: Clockwise (0→4096)
- Feedback: Load, position, operating speed, input voltage, operating current, operating temperature
- Electronic Protection: Overload, overcurrent, overvoltage, overheat
- Overload: Triggers when stalled torque exceeds 80% of stall value for 2s; cleared by sending new position command. Customizable torque threshold/duration.
- Overcurrent: Disables output when current >2A for 2s; cleared by sending new position command. Customizable current threshold/duration.
- Overvoltage: Activates when voltage >7.4V or ＜4V; auto-recovery within normal range. Customizable voltage range.
- Overheat: Disables torque output when temperature >70°C.
- Operating Modes: Mode 0, Mode 1, Mode 2, Mode 3
- Mode 0: Angle Servo (default; 0-360° absolute positioning)
- Mode 1: Speed Closed-loop Motor (maintains speed under load)
- Mode 2: Speed Open-loop Motor (speed drops under load)
- Mode 3: Stepping Mode (incremental motion from current position)
- Multi-Turn Mode: ±7-turn absolute positioning at maximum precision (turn count not saved after power loss).
- Center Calibration: One-click midpoint setting at any 360° position.
- Load lifespan: >100,000 cycles
- Motor noise: 45±5dB
- Servo noise: 65±5dB
- Storage temp: -30°C to +80°C
- Operating temp: -10°C to +60°C
- Max update rate: 1ms
- High-level voltage: 2-5V
- Low-level voltage: 0-0.45V
Suited to robotic arms, educational robots, quadruped robots, humanoid robots and small-scale sorting systems.
Jargon buster
Plain-language definitions for the technical terms used above.
- baud
- Baud is the signalling rate of a serial connection, often used as the speed setting for UART communication. Matching the baud rate matters because both connected devices must use the same setting for readable data.
- DC
- DC means direct current, where electricity flows in one constant direction, as supplied by batteries, USB ports and many plug-pack power supplies. When a product specifies DC, it runs from a DC supply rather than mains AC, so you need to provide the correct voltage and polarity.
- encoder
- An encoder is a sensor that converts the rotation or position of a shaft, knob or dial into electrical signals, reporting movement as incremental steps and direction, or as an absolute position. It is used to track how far something has turned, which matters for precise positioning, speed control, repeatable movement, or using a rotary knob as an input.
- GND
- GND is the ground or reference connection (0 V) for a circuit. When connecting two devices together, their grounds must be joined so both agree on what counts as a low or high signal.
- potentiometer
- A variable resistor usually turned with a knob or shaft to create an adjustable electrical signal. It is often used for inputs such as volume, brightness or position, so it helps beginners learn how a microcontroller reads changing values.
- servo
- A servo is a motor with built-in position control, usually told to move to a specific angle by a control signal. It matters when you need repeatable movement, such as steering, arms, flaps, or linkages, rather than continuous spinning.
- Stall torque
- The maximum twisting force a servo can produce when its output is held still and cannot move. It helps you judge whether the servo is strong enough for a robot joint, steering linkage, or other load.
- Torque
- A twisting force that causes something to rotate, usually measured in newton-metres or kilogram-centimetres. It matters when choosing motors, servos, gears, and tools because higher torque is needed to lift heavier loads, turn larger wheels, or move mechanisms without stalling.
- UART
- UART is a simple asynchronous serial interface that sends data over separate transmit and receive wires, usually labelled TX and RX, with both ends set to the same baud rate. It is a common way for microcontrollers and other serial devices to exchange data.
- VCC
- VCC is the positive power-supply connection on a chip or module. Connecting it to the correct supply voltage is needed for the part to power on and helps avoid damaging the electronics.
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