Download Fan Transfer Function Lab Report

Fan Transfer
Function Lab
Report
Elec 320-03
Andrews, David L.
Abstract:
Using the voltage sweep labview vi, it is possible to measure the effect a change in
voltage has on the speed of a fan. Two graphs are generated by the voltage sweep
program; the first measures Voltage vs. fan speed, another measures the sensitivity to
voltage.
Introduction:
The method by which the fan speed is measured introduces a new type of circuit;
an infrared transmitter and receiver.
Experimental Procedure
Set Up:
1. Four pre-assembled fan circuits are provided. Two graphs are generated for each
2. Hook up the labeled ports to their respective wires; Ground, DMM, etc.
Procedure:
1. Using the given “Voltage Sweep” labview program, sweep the voltage going
through the circuit from 5 to 12 volts.
2. Observe the change in
Illustration of set up:
Shown below is the circuit used for this experiment. The circuit itself is prearranged on the shown breadboard, with the fan permanently fixed in place. An
infrared LED and phototransistor are positioned so the fan blade interrupts their
connecting light. The infrared LED can be seen in front of the fan below. Appropriate
hookup points (DMM, 25v, etc) are listed on the breadboard.
Results
For this experiment, three different fans are used; alpha, beta and gamma. Below
are the voltage sweep and sensitivity graphs for each fan.
Voltage sweep graphs: the x-axis is voltage, the y-axis is the fan speed.
dy/dz graphs: the X-axis is voltage, the y-axis is the fan sensitivity to voltage, units of
Hz/V
Fan Speed
α Alpha fan voltage sweep
Voltage
Voltage Sensitivity
α Alpha fan voltage sensitivity
Voltage
Alpha Fan
Fan Speed
β Beta fan voltage sweep
Voltage
Voltage Sensitivity
β Beta fan voltage sensitivity
Voltage
Beta Fan
Fan Speed
γ Gamma Fan Voltage Sweep
Voltage
Voltage Sensitivity
γ Gamma Fan Voltage Sensitivity
Voltage
Gamma Fan
Discussion
Each fan is designated two graphs, voltage vs speed and voltage vs.
voltage sensitivity (Hz/V). For the Voltage Sweep Graphs, the linear
increase in speed shows
The labview program in use performs a controlled voltage sweep from
5 to 12 volts through the DC motors. At the same time the fan speed is
measured by how often the connection path between the infrared LED and
a photocell is broken by a fan blade. This process shows the relationship
between fan speed and applied voltage. When finished, the program graphs
out the voltage vs speed as measured in Hz by the LED and photocell.
Fan
Three Schematics: The Setup, The Circuit diagram, and the resultant signal.
The same program also displays the derivative of the first graph,
dF/dv. This derivative shows the DC motors sensitivity to voltage in Hz/V,
is almost constant over the range of voltages. This fact agrees with DC
motor theory.
This lab is also an example of a phototransistor circuit. As the fan
blade repeatedly cuts off the connection between LED and Photocell, a
square wave is created.
Each fan has a linear dependence on voltage, however each rings out
at a different final speed at 12V.
Fan Speed @
12v
Slope of line
Sensitivity to
Voltage dy/dv
Alpha
300 Hz
Beta
225
Gamma
235
25.7
22.5
22.14
16.5
23.57
22.5
The full controller interface created in labview is shown below.
Conclusion
The voltage sweep of each fan showed that the fan speed does have a
linear dependence on the voltage. The voltage and fan speed may always
hold a linear relation, however each fan has slightly different slopes and
final values. The fastest fan is Alpha, reading 300 Hz at 12v.