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.
PCB Motor Mount
If you don't have a home machine shop or 3D printer, you can make a motor mounting bracket from a PCB.
Printed circuit boards are strong, lightweight, precise, and are easily manufactured.
The PCB bracket can then be attached to your project using screws, straight solder, right-angle headers, or dual-row headers.
The video in the article shows you the process step-by-step, including how to make the board non-rectangular and how to place screw holes at angles.
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.
Sturdy Attachment of a Lego Wheel to a Gearmotor
Nothing is more pathetic than a robot that has lost a wheel.
Couplings based on the standard mating cross axle have a habit of sliding off.
But, the peg holes present in larger wheels provide opportunities to securely attach the hub with screws.
Using a lathe, milling machine, digital readout, magnets, PVC plastic, and a carefully-drafted layout can produce a rugged Lego coupler.
Ah, an article on math and machining; what could be more universally appealing?
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!