For a controls lab using an arduino, thermistors and fans, answer the following

Question

For a controls lab using an arduino, thermistors and fans, answer the following questions:

Explain in 25-100 words. Which fan (2, 3 or 4 pin) is the best for variable speed control using an external fixed voltage? Explain in 25-100 words. Why are we not able to drive the 3 pin fan to the max speed using the Arduino Uno? Explain in 25-100 words. Why are we able to drive the 4 pin fan to its max speed using the Arduino Uno? Explain in 25-100 words. How is the way we control a 4-pin fan similar to how we control a servo motor? How is it different? Explain in 25-100 words. What are the advantages of using a PWM signal over voltage control?

Explanation / Answer

3. Fan 4 is best for variable speed control as it consists of a specialized PWM pin which can be driven from an Arduino using a small signal NPN transistor, a small signal N-channel mosfet, or even just a diode.2- and 3-pin fan speeds can only be changed by altering the voltage supplied to them.

4. Because the 3 pin fan doesnt have a specialized PWM pin for speed control (please see answer 7 and add part of it here)

5. Because the 4 pin fan has a special pwm pin for speed control due to which we can drive it to maximum speed or 100 % duty cycle.In PWM control voltage supplied to the motor is the full +12VDC for some of the time.PWM has a lower value of form factor accounting for heat dissipation making it possible to drive motor at higher speed.(Please see answer 7 and add part of it here)

6.Like 4 pin fan, Servos are also controlled by sending an electrical pulse of variable width, or pulse width modulation (PWM), through the control wire.In servos, PWM sent to the motor determines position of the shaft, and based on the duration of the pulse sent via the control wire; the rotor will turn to the desired position.In 4-Pin fan PWM is used to control the speed

7.In a voltage control mechanism the switching power dissipation will be higher as voltage pulses are continuously switched for Speed control in a Fan. Whereas pulse width modulation results in a smaller losss in switching power of transistor as the transistor either remains on or off .Thus switching transistor will have a much reduced power dissipation due to which motor will possess a linear type of control and better stability overall

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