When you want to make any electronics project that uses motors there are a couple of problems. What motor configuration will I use, how big, how strong, what kind, what rotation speed and power supply is needed for my type of motor are some of those problems.
First we need to decide what motor configuration we use. For example if we use wheels here are some possible configurations:
2 wheels connected to one motor for propulsion and another 2 wheels to a second motor for steering (like a real car);
2 wheels each with its own motor and another wheel for balance (configuration also called differential drive, for example used by tanks);
2 wheels using two motors but no third wheel for balance. (used for pendulum like robots).
There are three standard types of motors generally used for DIY electronics projects: brushed DC motor, servo motor and stepper motor. Each has its own pluses and minuses.
Brushed DC motor
They are easy to find and they come in many sizes and shapes. This kind of motor has a high rotation speed, that way if you want to get a high torque you need a gearbox. Also it needs a supply voltage from +3V and above. DC motors are hard to mount on wheels and use high current for higher torque. To control this type of motor you will need to know how to use the PWM and also you may need a motor controller (for example a double H bridge for both clockwise and counterclockwise). Brushed DC motors are expensive and are best used for powerful robots or for robots that need a very high torque.
Stepper motor
It’s a brushless DC motor that can make a full rotation in a certain number of steps. There are different sizes and shapes of this type. You can precisely control and position them. To command such a motor you will need a stepper motor controller (for example you can even use a simple H bridge). But this kind of motor has some more disadvantages. The stepper is a big, heavy motor, which uses a lot of current but doesn’t have a great torque and is hard to mount on wheels. The stepper motor is best suited for DIY electronics projects that need a very accurate control of low weight movement.
Servo motor
Basically it’s a brushed DC motor that has a control circuit, a potentiometer and a gearbox. But a big difference is that the standard servo can be positioned by sending the right signals to a specific angular position. To control this type of motor you need to send pulses every 20 milliseconds with width of 1.5 ms for 90 degrees, 1.25 ms for 0 degrees and 1.75 ms for 180 degrees. Servos are the most common motors used in DIY projects because servo motors are cheap, light and easy to mount on wheels or other mechanical structures.
This kind of motor uses a power supply from +4,8V to +6V, and they have a medium current use. That’s why they are usually connected to battery packs. Servo motors have 3 wires with different colors, depending of the manufacturer, but with the same use: power, ground and control wire. The motor can be modified to make a 360 degrees full turn. This is very useful because you will need only one control pin and not two like the dc motor. Servos are best used for low weighted projects like small robots or even robots that use legs for locomotion.
