DFRobot
ST3215 Serial Bus Servo 19.5kg.cm 7.4V 360° Encoder
· MPN: SER0069
Built for demanding multi-axis robots, this smart serial bus servo combines high torque, absolute position feedback and simplified wiring over a TTL serial b...
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Built for demanding multi-axis robots, this smart serial bus servo combines high torque, absolute position feedback and simplified wiring over a TTL serial bus. It is suited to projects such as robotic arms, educational robots, quadrupeds, humanoid robots and small-scale sorting systems.
The servo uses a 12-bit magnetic encoder for true 360° absolute position sensing, with 4096 steps and 0.088° per step resolution. It also supports ±7-turn multi-turn absolute positioning for movements beyond a single rotation.
Control is via half-duplex UART, allowing up to 253 servos to be daisy-chained from a single host I/O port. Each servo can be assigned its own ID, reducing cable clutter in complex robotic builds.
The package includes one ST3215 Serial Bus Servo, a servo horn screw accessory kit and a 3-pin servo cable.
Features:
- Serial bus control: TTL serial bus interface for controlling up to 253 servos from a single port
- Magnetic encoder: 12-bit high-precision magnetic encoder for 360° absolute positioning
- High resolution: 4096 steps with 0.088° per step
- Multi-turn positioning: ±7 turns absolute positioning
- High torque: 19.5kg·cm stall torque at 7.4V
- Gear train: 1:345 gear train made from copper and aluminium
- Housing: High-strength PA+GF housing
- Operating modes: Angle Servo Mode, Speed Closed-loop Mode, Speed Open-loop Mode and Stepping Mode
- Feedback: Real-time feedback on position, speed, load, input voltage, current and internal temperature
- Protection: Built-in protection against over-stall, over-current, over-voltage and over-heating
Specifications:
- Operating voltage: 4-7.4V
- No-load speed: 0.238s/60° (42RPM)@6V；0.192s/60° (52RPM)@7.4V
- No-load current: 130mA@6V；150mA@7.4V
- Stall torque: 16.5kg.cm@6V；19.5kg.cm@7.4V
- Stall current: 2A@6V；2.5A@7.4V
- Standby current: 6mA
- Rated load: 4kg.cm@6V；5kg.cm@7.4V
- Rated current: 500mA@6V；650mA@7.4V
- Motor resistance: 2.5Ω
- Torque constant (Kt): 8kg.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
- 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.
- 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: 60±5dB
- Storage temp: -30°C to +80°C
- Operating temp: -20°C to +60°C
- Max update rate: 1ms
- High-level voltage: 2-5V
- Low-level voltage: 0-0.45V
A strong fit for robotics builds that need compact wiring, position feedback and programmable motion modes over a UART bus.
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.
- 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.
- 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.
- TTL serial
- A simple serial data connection that uses microcontroller logic-level voltages (typically 3.3 V or 5 V) rather than the higher, inverted voltages of computer RS-232. When a device lists TTL serial, it can usually wire straight to a microcontroller's UART pins or to a USB-to-TTL serial adapter, but it needs a level converter before connecting to a true RS-232 port.
- 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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