Lecture 2: Bits, Bytes, and Intro to the Galumphing Robot Project Professor Carr Everbach Course web page: http://www.swarthmore.edu/NatSci/ceverba1/Class/e5/ 10 Years Ago   A moment of silence and reflection…
Remember…   Wizards available Tuesdays/Wednesdays 7:00-10:00 pm (Hicks
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213) for Engin and Sundays/Tuesdays 7:00-9:00 pm Physics &
Math
Thursday 9/8 – your personal web page is due
Friday 9/9
  Tennis Ball Drop starts at 3:30 pm. Choose one person to
describe your design in about a minute (for the video).
  Engineering Department Picnic starts at about 4:30
  Add/Drop period ends
Next Thursday 9/15
  Tennis Ball Report (on website) is due
  Short response essays on Fork and Mirrored articles due
Shop class (not required – only if you are interested). Starts
9/16 (Friday). Sign up is in Engineering Department Office.
Also…   Paolo-­‐Alexander Debuque left his iPod touch in this room on Sunday. Anyone see it?
The Big Picture The next 7 weeks we will be building and programming
one-armed robots. You will also be learning Matlab™,
and will be individually responsible for completing the
assignments. Solutions should be uploaded to Moodle,
so please log in to check.
Today we’ll review basic concepts of digital
representation and control. In lab this week, we’ll visit
the Machine Shop and play with servo motors. Next
week, I’ll start teaching Matlab, but you can start
reading Chapter 1 of the Palm text now.
Bits, Bytes, and Words   Basic unit of digital information is a “bit.”   TTL: zero volts vs. 5 volts   CMOS: -­‐3 volts vs. +3 volts   Coming soon: Memristors   Each Bit uses approximately 1 transistor in silicon   Byte = 8 bits (MB = 1 million bytes = 8 million bits)   Densities ~ 100 MB/cm2 in VLSI   Memristors ~20 GB/cm2   CD example CD example   1 bit = 2 possibilities   2 bits = 4 possibilities (00, 01, 10, 11)   N bits = 2N possibilities   On CD, 44,100 samples/second, 2 channels   16 bits/sample (2 Bytes) = 216 possible voltages = 65,536   How many bytes on a 70-­‐min. CD? 2 bytes • 44,100 samples/sec • 60 sec/min • 70 min • 2 channels 740,880,000 = 740 MB Genome Example   Human genome has 3 billion nucleotides   Each nucleotide can take one of 4 possible values: Adenine, cytosine, guanine, thymine   How many bytes is this?   3 billion nucleotides • 2 bits/nucleotide = 6 billion bits   6 billion / 8 bits = 750,000,000 = 750 MB DNA density: 1 EB/mm2 Servo Motors (1)   Output shaft of motor turns to angle specified by input pulses.   We send a stream of pulses to servo through wires connected to it.   Width of pulses defines angle of output shaft. http://www.lynxmotion.com/images/Products/Full/hsr-5980.jpg
Image adapted from: http://www.electronicsteacher.com/robotics/images/pulsewidthdiagram.gif
9 Servo Motors (2) Relatively precise, but not accurate
Images adapted from: http://www.lynxmotion.com/images/data/ssc-32.pdf
10 Controlling the Servo   Open a serial port connection
  Send a string of characters to the I/O board
  The I/O board controls the motors by
varying the width of pulses sent to the servo
11 Control Format #<ch>P<pw>...#<ch>P<pw>T<time><cr>
  <ch> = channel number (0-31)
  <pw> = pulse width in microseconds (500-2500)
  <time> = time in milliseconds for move (optional)
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<cr> = carriage return
http://www.youtube.com/watch?v=Pp2IJIk5qvc
12 Control Format Examples #<ch>P<pw>...#<ch>P<pw>T<time><cr>
  Sending the string:
‘#1P1500T200<cr>’
  ch=1, pw=1500, time=200
  This will set the pulsewidth on motor 1 to 1500
microseconds, and will make the change over 200
milliseconds. (1500 ms ≈ 0°)
13 Another Control Format Examples #<ch>P<pw>...#<ch>P<pw>T<time><cr>
  Sending the string:
‘#1P900T300<cr>’
  ch=1, pw=900, time=300
  This will set the pulsewidth on motor 1 to 900
microseconds, and will make the change over 300
milliseconds. (900 ms ≈ -45°)
14 Control Format Example Again #<ch>P<pw>...#<ch>P<pw>T<time><cr>
  Sending the string:
‘#1P1200#5P2100T1500<cr>’
  ch=1, pw=1200
ch=5, pw=2100
time=1500
  This will set
  the pulsewidth on motor 1 to 900 microseconds,
  the pulsewidth on motor 5 to 2100 microseconds,
  and will make the change over 1500 milliseconds.
15 Servo motor demo Ball Drop Teams Dana-­‐Hallowell
Parrish and off-­‐
campus folks Wharton
Mertz
Alice Paul-­‐ David Kemp
Mary Lyons
Hicks 303
Hicks 301
Hicks 310
Hicks 309
Hicks 312
Hicks 308
Willets Hicks 314