This breadboard-compatible module is an alternative to bulky power switches. It uses a small integrated slide switch to control a high-side power MOSFET that can deliver continuous currents up to around 16 A at 4.5 V to 40 V. The board features reverse-voltage protection and also makes it easy to control the MOSFET with an external switch or the digital output of a microcontroller.

This compact, inexpensive plastic gearmotor (brushed DC motor with a 120:1 reduction gearbox) is well suited for use in small robots. While intended for operation at 4.5 V, it should run comfortably in the 3 V to 6 V range.

This compact, inexpensive plastic gearmotor (high-power brushed DC motor with a 120:1 reduction gearbox) is well suited for use in small robots. While intended for operation at 4.5 V, it should run comfortably in the 3 V to 6 V range.

This item is a set of three plastic rollers, a 1″-diameter plastic ball, and a retaining clip that can be used on the front or back ball caster locations on the Romi chassis base plate. The ball is white, and all other parts are red. It is included as part of the red Romi Chassis Kit.

This synchronous switching step-down (or buck) regulator takes an input voltage of up to 40V and efficiently reduces it to 5V with an available output current of around 15A. Typical efficiencies of 80% to 95% along with its high current capabilities make this regulator well suited for powering large loads. Pololu 2881

This synchronous switching step-down (or buck) regulator takes an input voltage of up to 40 V and efficiently reduces it to 3.3 V with an available output current of around 15 A. Pololu 2880

This synchronous switching step-down (or buck) regulator takes an input voltage of up to 40 V and efficiently reduces it to 6 V with an available output current of around 15 A. Pololu 2882

The FS5115M is a standard-size analog servo from FEETECH that has an all-metal gear train and delivers extra-high torque normally associated with much more expensive or larger servos. Servo horns and associated hardware are included. Pololu 3426

The S9V11MA switching step-up/step-down regulator efficiently produces a finely adjustable output between 2.5 V and 9 V whether it is higher or lower than the input voltage, which can range from 2 V to 16 V.  Pololu 2869 

The stepper motor driver with the MP6500 system allows the bipolar motor to be supplied with current up to 1.5 A per phase, without the use of a heat sink. The system can be supplied with voltage in the range 4.5 ... 35 V. Pololu 2966

TB67S279FTG stepper motor controller module supplied with 10 ... 47V voltage and 1.2A working current. The controller allows you to control the motor movement up to 7 different resolutions (up to 1/32 of a step). Pololu 2974

TB67S249FTG stepper motor driver module supplied with 10-47V voltage and working current of 1.7A. The controller allows you to control the motor movement up to 7 different resolutions (up to 1/32 of a step). Pololu 2973