DC Motor Reflection

Component selection

Since our purpose was to achieve Clino-rotation so components were being selected to fulfill that requirement.
DC motors

To achieve the purpose of rotation in our one axis clinostat we have selected the DC motors because the voltage rating of DC motor is less which makes the system energy efficient, it is easy to procure, small in size plus weight and less in cost. The motor we have selected is RF-370CA-15370. Fig. 3.1 displays the internal cross section of DC motor and shown in APPENDIX F are its basic ratings. Fig.3.1. DC motor

“It converts DC electrical power into mechanical power”
If a conductor carrying some current is placed in a magnetic field it will experience some torque and tend to move. This is the basic

Working of DC motor [9]
In Fig. 3.4, the DC motor is represented with a circle with which brushes are attached. With the brushes the supply terminals are connected. With the supply terminal armature resistance is also connected in series. On the output side a shaft is attached with the armature, these both are coupled to handle the mechanical load.
When an input voltage is applied across the terminals of the motor an electrical current flows across the rotor through brushes. Then due to the presence of magnetic field a torque is produced and because of this torque the armature of the motor is rotated.
Stepper Motor

For the two axis rotation Clinostat along with the DC motors we had to use a stepper motor because it has the ability to bear large loads remaining with in a sufficient voltage range. On the other hand in DC motors, as we increase the load the operating voltage of the motor with a load increases and in turn motor size and weight increases. Another purpose behind selecting the stepper motor is that its RPM can easily be varied by simply varying the delay between each of the step we feed to the motor via microcontroller. The stepper motor we choose is

3.5 displays the detailed cross section of stepper motor and further details about the motor can be seen in APPENDIX G. Fig.3.5. Cross section of stepper motor [10]
“A stepper motor is a synchronous brushless electrical motor which converts digital pulses into a mechanical output.” [10]
In stepper motor each rotation is divided into a fixed number of steps. Each step receives a separate pulse at a time and takes one step at a time. And hence each pulse results in the rotation of the motor at a precise angle. Like DC motor it does not require any feedback mechanism for its control.
When the delay of the pulses is varied via micro controller stepping movements of the motor convert into a continuous rotational behaviour where the velocity of rotation is inversely proportional to the delay between the control pulses.
Stepper motors are evidently used because of their low cost, high reliability, and high torque at low speeds.
Step Modes [10]

There are three basic step modes for a stepper motor; full step, half step and micro step. The step type depends upon the type of stepper motor driver being used. Full