Cheap Powerful Electric Gearmotors

Bought 2 powerful motors for a mini sumo from Ebay for $11 each.

12V 1000RPM Torque Electric Gear Box Motor

Specifications:

• Static Torque: 1.5 N*cm
• Voltage: 12V DC
• RPM: 1000RPM
• Diameter: 25mm
• Length: 52mm
• Shaft diameter: 4mm (D-profile)
• Weight: 76g

Measured parameters:

• Inductance: 0.9 mH
• Resistance: 2.5~3 Ohm
• BEMF or Torque constant: 0.112
• Inertia: 1.071e-4 kg*m^2
• No-load Current: 0.11 A at 12V
• No-load Torque: 1.232 N*cm
• Electromagnetic time constant: 0.36 ms
• Mechanical time constant: 21.34 ms

By connecting a signal generator to a motor with a resistor in series to measure current with an oscilloscope.

Image from DSO203

Measure Time Constant of a dynamic process and multiply it with Full active resistance in series, to find out the Inductance.