How to Connect Motors to Your Robot or Electronic Project

Movement differentiates a robot from just another electronic device. Choosing the right size motor, based on voltage, current, efficiency, weight, size, gearing, torque, and speed makes the difference between success and failure.

A small DC (direct-current) electric motor can be easily controlled by a single transistor and diode if you simply want to start and stop it. You can even electronically control motor speed using pulse-width modulation. However, to change directions, you'll need an H-bridge or motor driver chip.

Many builders struggle with attaching the motor to the robot or connecting a wheel to a motor. In fact, I've probably written more articles on making motor couplers than anything else.

Bipolar Transistor H-Bridge Motor Driver
For battery-powered (low voltage, low current) motor operation, the classic discrete-transistor bipolar H-bridge beats most MOSFET and prepackaged motor driver chips for most hobbyists. But, are some of the newer transistors better in this well-known hbridge design over the common 2222, 2907, 3904, or 3906 TO-92 transistors?

Pulse-Width Modulation (PWM) for Motors and LED Displays
Variable duty-cycle PWM is a great method for controlling the speed of a DC motor and the brightness of an LED display. You can make a simple PWM circuit (without a microcontroller) by using off-the-shelf electronic parts such as an inverter chip, diodes, a capacitor, and a potentiometer.

Mounting Motors and Attaching Wheels
Three different ways of connecting wheels to motors and securing motors to robot platforms. Includes drilling a pair of glued LEGO bricks, a solid UHMW coupler rod, creating motor mounts from aluminum angle stock, and a v-groove belt pulley system.

Faulhaber Gearmotor with Encoder and Right-Angle Shaft
A number of surplus sites are selling a compact, low-current motor that is perfect for robotics. The 6V motor includes a 141:1 gearhead, a magnetic quadrature encoder, and a 90-degree output shaft.

DPDT Bidirectional Motor Switch
Controlling a motor in both directions (and on/off) with a single physical switch. You can control a motor without any transistors or chips.

H-Bridge Motor Driver
A wiring diagram, photograph, and movie of an H-bridge dc motor driver circuit implemented with a TC4424A, TC4427A, MAX4427, or IXDN404 dual MOSFET driver IC. Very useful for running small bot gear motors.

Motor Mount Clamp Block
Sometimes, a small electric motor will lack mounting screw holes. Other times, a robot or device needs several things tied to the motor mount. A simple slitted block with screws can securely hold a motor in ways that other mounts cannot.

An Aluminum LEGO Hub Made on a Mill
Because LEGO tires, gears, and axles are great for building robots, I keep coming up with new adapters to connect them to standard motors. This latest method applies to the LEGO wheels that don't have cross-axle holes. Couplers and hubs are best made on a lathe, but this shows that you can create miniature round parts on a mill.

Making a Lego Wheel to Gearhead Motor Coupler on a Lathe
Lego has some fantastic wheels to use on robots. But, Lego doesn't have a wide selection of motors. Here's how you can machine an adapter on a lathe to use Lego tires with off-the-shelf gearhead motors.

Tiny Motors
Miniature motors are wonderful for B.E.A.M. robots or moving small loads. A plentiful source of inexpensive commercial motors are those used as vibrating alerts in pagers and cell phones. But how does one remove the metal offset weight?

Motorizing a Shear for Cutting PCBs
Machining a motor coupler with a round hole and a square hole. Making a motor mounting bracket adapter. Damage assessment of an over-torqued gearmotor.

LEGO MindStorms Crown Gears
There are at least three variations of the LEGO 24-tooth crown gears. Watch out that you don't accidentally mismatch pairs!