DC motors

A DC motor is designed to run on, what do you know, DC electric power! There are by far two common kinds of DC motors, the brushed and brushless types. However, these two types use certain forms of commutation, internal and external respectively, which create an oscillating AC current from the DC source.

Two pole DC motor:

A simple DC electric motor. When the coil is powered, it generates a magnetic field around the armature, which is the bit in the centre that is rotating. The left side of the armature is pushed away from the left magnet and the right side is pushed away from the right magnet.

Armature continues to rotate.

The commutator reverses the direction of the current through the coil, reversing the magnetic fields. The process repeats itself.

However, DC motors are designed with more than two poles and can start at any position. Current flowing through the coil will also definitely start the motor moving.

So as we see from above, the DC motor can operate in quite a simple manner. Connect voltage to the terminals of the motor, and the motor shaft spins. Since the motor is non-polarized unlike the solenoid that was mentioned in the previous post, it can spin in the opposite direction. Just reverse the wires connected to the motor. Now to spin the motor at a slower speed? Just lower the voltage connected to the terminals. Spinning faster would require more voltage. But what if I want to know exactly what voltage a motor should get? What’s the difference between 48V and 12V?

Voltage

Typical motors used in hobby robotics are rated at about 6V to 12V. Larger ones used in heavier hobby robotics are usually rated at about 24V or more.

So why do motors operate at different voltages? We know that voltage that a motor runs at affects the motors torque, so more voltage, more torque. However, you definitely should not be running your motor at voltages way above the recommended ratings like running a 12V motor at about 120V. This is dangerous and could melt the coils in the motor. A DC motor’s rated voltage is the voltage at which it runs the most efficiently. Keep it safe, and try to apply voltage as close to the recommended voltage as possible.

Do keep in mind that if you want to use a 24V or more motor on your robot, your robot must also be able to carry a battery that can supply that amount of voltage (which are heavier, bulkier and bigger). So unless you really need the torque to power your robot, stick to the 12V motors.

Will have more information on DC motors coming up in this post as soon as I find the time to write :)