Page 131 - Build Your Own Quadcopter_ Power Up Your Designs with the Parallax Elev-8

110 Bu il d Y o ur O w n Q u a d c o p t e r

numbers, as you can see in the figure. In this screenshot, I started with 0 and then entered 1,
2, 3, and 0. The demo program is designed to start with 0% power so that you don’t get
startled when you press the space bar. That is all that is needed to run this experiment, and
in the next section, I will both show and discuss the results.

Experimental Results
Timing measurements were based on the waveform diagram shown in Figure 5.22. The
pulse width is T1, and the spacing between pulses (period) is T2, as shown in the figure.
In Table 5.3, you see the combined results of running the motor with and without the
propeller. Obviously, no thrust readings were possible without the propeller attached, but it
was possible to capture all the timing readings. Some results, such as those for power, are
computed from other table values.
The x's in the Table 5.3 indicate which measurements were not taken because of excessive
vibrations or because the limits of the measuring instruments were exceeded, or both.
Nonetheless, I was able to record a reasonable set of performance figures for low- to medium-
speed operation. Figure 5.23 shows a chart of thrust versus power level, which appears to be
a reasonable curve based on my research.
Figure 5.24 shows a chart of r/min versus thrust, which is a common method used to
assess the performance of a propeller and is discussed in a following section. I also added
an additional data point that I estimated from the trend of the actual data points. This
estimate reveals that 860 grams of thrust will be generated when the propeller is spinning
at 7000 r/min.
Figure 5.25, which shows the power consumed versus propeller r/min, is the final chart
that I will show. I added an additional data point that I estimated from the trend of the actual
data points. This estimate reveals that 150 watts (W) of power will be required to spin the

Figure 5.22 Waveform measurements diagram.