# Introduction to Robotics/Sensors/Lecture/Students

Name:_________________________________

Date: 10 / 17 / 2019
Sound Waves

Speed of sound
${\displaystyle D=Ct}$
D is the distance, measured in meters.
C is the speed of sound in air, measured in meters per second.
t is the amount of time the wave travels, measured in seconds.
At 72°, sound travels at 344.8m/s.
Convert to Centimeters
We convert to centimeters because they are more useful, and it helps to remove fractions from our calculation.
${\displaystyle D=Ct\times {\frac {100cm}{1m}}=100Ct}$
For the BoeBot
${\displaystyle D={\frac {100CT}{2}}}$
Because the sound wave must travel to the object and back.
The BoeBot measures t in "clock cycles", which are each 2μseconds. We must convert the equation to use seconds instead of clock cycles:
${\displaystyle D={\frac {100Ct}{2}}\times {\frac {2}{1,000,000}}={\frac {Ct}{10,000}}=0.03448t}$
Fractional Math
The BoeBot can do some limited math with fractions.
The "**" operator is used as follows:
${\displaystyle A**B=A\times {\frac {B}{65536}}}$
We calculate that:
We can use the following code to convert time to distance:
Distance = Conversion ** time
Finding the Conversion Constant
${\displaystyle Conversion=0.03448\times 65536=2260}$