~ Different types of motor and their uses ~
If you want your project to have some form of movements, linking a motor to some mechanism is one effective way of achieving the purpose. Whether it is to rotate a platform, or to swing a door, or to manipulate a lever, a motor can be the power source to operate the mechanism. However, you have to select thecorrect type of motor to match the job. Using the wrong motor would result in under-performance and in the worse case, the project ending in a complete failure. The following is an introduction to the different types of motor and their applications.
1. DC Motor
This is the most common type of small battery-operated motor that can be used for a variety of projects. The main advantage is their smallsize and they do not require complicated control. It can be connected directly to the rated battery voltage for simple functions. Straight from the box, a typical DC motor spins in excess of 15,000 rpm (revolution per minute), which is way too fast for most applications. To be useful, it must be geared down to the appropriate speed. Another reason for gearing down a DC Motor is to increase thetuning torque (turning power) which is required to do useful work.
Because of their small sizes and easy control, DC motors find many uses in modern appliances. They can be found cooling power supplies and CPUs in PCs and operating CD ROM drives. Printers use a few of them in each unit to feed paper to the print head. As a result, they can be found easily in used equipment and modifiedto for use in a project. However, it is important to note that DC motors are not very precise in their operations. Their speed can vary quite a bit even under the same operating condition. This is especially the case when they are under load.
When selecting a DC motor, ask yourself the following questions:
What is the load it is expected to bear? This is the turning torque ofthe motor and is measured in kg.cm. If the expected load is higher than the motor’s rating, it would heat up very quickly when in use and will soon breakdown. This is a very common cause of motor failure in projects. Always cater for some extra allowance in your selecting the power rating. For example, if your project requires 3 kg.cm force, then choose a unit that gives 6kg.cm force. This wouldprevent motor failure in the event of the mechanism becoming jammed, which is quite common in the development stages.
What speed is the motor expected to turn at? Motor speed is measured in rpm. In applications where the speed is an important factor, it would have to be reduced by a series of gears. Some motors are sold with gear box with user-selectable ratios. These allow the user to select thegear ratio by interchanging the positions of the gears to arrive at a suitable speed for the output shaft. Further speed refinement can be done with an electronic speed controller.
DC Motor Control
Some kind of control circuit is required if you need the motor to do more than just spinning. An example is when a motor is used to slide a tray open and close. The motor will need to turn in onedirection to open the tray and stop. This is followed by turning in the opposite direction to close the tray. The control circuit would have to accept a signal to turn the motor in one direction and reverses it when a second signal is received to close the tray.
The example cited above is relatively easy. It can be accomplished by means of some switches connected together. For more complicatedmovements, an intelligent controller would be required. These may include movements that return the output shaft to the original position or one that requires several stops in one revolution.
2. AC Motor
AC motors are complicated electrical equipment. They are mentioned here just so that you know that there is such a type of motor. Unlike DC motors, they cannot be powered by batteries and requires...