This motor is a small brushed DC gear‐motor with a built‐in metal spur gearbox (reduction) plus an encoder for feedback. It’s designed for low‐voltage operation (typically 3 V), low output speed (~50 RPM), compact size, and is often used in robotics, small mobile platforms, automation projects, hobby builds, or situations where you need both mechanical reduction and feedback (for position/speed).

Its small size, metal gearbox and encoder make it a good match for micro robots, actuator tasks and embedded systems. However, because of its size, it is limited in torque and precision (encoder resolution) and should be used within its design envelope.

Features :

• Encoder: Built‐in encoder giving pulses per revolution (PPR) on the output shaft or motor shaft (depending on variant). Example: an encoder with ~7 PPR (pulses per revolution of the motor or output) was stated in one datasheet.
  • Encoder interface: may have wires for encoder + motor power. For example: motor power wires + encoder Vcc, GND, A phase, B phase.
• Very compact size and low voltage (3 V) makes it ideal for battery‐powered mobile/robotic projects.
• The gearbox gives low output speed (50 RPM) which often means higher torque at output, useful for driving wheels or mechanisms.
• Having an encoder built‐in provides feedback for speed control, position tracking, closed‐loop control (e.g., with microcontroller).
• Metal gear version increases durability compared to cheaper plastic gearboxes.
• Many variants available (different voltages, speeds, gear ratios) so flexibility and parts availability in hobby/DIY context.

Specifications :

• Rated voltage: ~3 V DC. Some vendors state “Rated Voltage: DC 3V” for the 50 RPM version.
• Output speed (no‐load or approximate): ~50 RPM (for the gearbox output shaft) at rated voltage. 
• Gearbox reduction ratio: implied by speed vs motor raw speed; e.g., datasheet mention “When selecting 12 V version 200 RPM = 3V version 50 RPM” for one variant. 
• Dimensions / size: Typical motor body ~12 mm diameter (“N20” size), length varies; e.g., one listing shows length ~36 mm. 
  • Shaft: ~3 mm diameter output shaft (often “D-cut” type for better coupling) and ~10 mm length in many specs.
• Typical performance / currents:
  • No-load or low load current might be small (tens of mA) for the geared version. Example: ~10 mA no‐load for 3 V 50 RPM version.
  • Stall current will be much higher; for example one listing shows stall current ~1 A for 3 V version. 
  • Output torque will depend on gearbox reduction; some values given in kg‐cm in vendor specs. (For example: rated torque ~0.2 kg-cm, stall torque ~1.6 kg-cm in one listing) 
• Weight: Approx ~11 g for some gearbox+motor variant. 
• Shaft output speed / compatibility: Because the gearbox output is slow (50 RPM) the motor is suited for applications needing low speed and decent torque.
• Voltage flexibility: Some sellers note that although rated 3 V, the motor may run at higher voltages, but that will increase speed and stress the motor. For example, one listing for 12 V version says for 3 V target speed you select 12 V 200 RPM version.
• The motor body diameter is ~12 mm (hence N20). The gearbox is metal (metal spur) in many cases, giving durability and better torque than plastic gearbox versions. 
• The output shaft is ~3 mm diameter with a “D-cut” profile for locking wheels/pulleys. The shaft length is typically ~9-10 mm. 
• The motor has two main power wires for driving it (brush DC motor). Separately there are encoder wires for feedback signals.
• The encoder: often a Hall or magnetic encoder, providing A/B phase outputs (quadrature) so you get directional information, not just pulses. Example: A and B signals with enabling 3.3-5 V supply for the encoder electronics.
• For wiring: One vendor lists: Red = motor +, Black = motor –, Yellow = encoder signal A, Green = signal B, Blue = encoder VCC (or GND) etc. 
• Gearbox ratio: Varies by variant; for this 50 RPM version the ratio is likely high (to reduce speed to ~50 RPM). One listing mentions gear ratio ~200:1 for 3 V 50 RPM version. 
• Mounting: The motor and gearbox are compact, often with mounting holes on the gearbox housing or simple front output shaft for coupling. Check the specific variant for mounting hole pattern.

Applications :

These geared motors with encoder are widely used for small robots (wheel drives), precision positioning, smart lock actuators, automation modules, hobby projects, micro vehicles, etc.