Week 5 Lots of Stuff

1
Week 5 Lots of Stuff

• Sensors and sensing, mostly.

2
All of Todays Stuff

• Start Passing Wires Around
• printf() / just a few words /
• Serial Terminal
• Sensors and Sensing
• Voltage Divider Circuit
• Photocells
• Photovores
• Wiring

3
Start Passing Wires Around

• Youll need four 2½ long wires of different
  colors, stripped ¼ at both ends
• Red (5 Volts)
• Black (Ground)
• Blue (Pin C4)
• White (Pin C5)
• Also, two 1 long blue/yellow striped wires,
  stripped ¼ at both ends

4
printf()

• printf() is a formatted print function in C.
• It takes a variable number of arguments
• 1 printf(Hello, world!\n)
• 2 printf(This is an integer d\n, nameofint)
• gt2 printf(3 ints d, d, d\n, a, b, c)
• See analogbutt.c on Blackboard.

5
Serial Terminal

• No monitor hooked up to your robot!
• Buzzer
• LEDs
• RS232
• TeraTerm
• A (free!) terminal emulation software
• http//hp.vector.co.jp/authors/VA002416/teraterm.h
  tml
• StartgtRun Q\tt

6
Sensors and Sensing

• Sensors tell a robot one simple thing about their
  environment
• Temperature, distance, pressure etc.
• A digital sensor returns a 0 or a 1
• Example bump sensor
• An analog sensor returns a value from a range
  based on the voltage level.
• Examples photocell, ultrasonic ranger

7
The Voltage Divider
This is a battery. It supplies electrical
current at a constant(ish) voltage.


8
The Voltage Divider
This is a battery. It supplies electrical
current at a constant(ish) voltage.


6V
9
The Voltage Divider
This is a resistor. It blocks the flow of
electrical current.
10
The Voltage Divider
This is a resistor. It blocks the flow of
electrical current.
11
The Voltage Divider


V
R1
R2
12
The Voltage Divider

• a V
• c 0 (Ground)
• b (a-c)(R1/R1R2)
• V(R1/R1R2)

V
R1
R2
13
Photocells
Photocells are variable resistors. Current flow
is proportional to incident light.
14
Photocells
Photocells are variable resistors. Current flow
is proportional to incident light.
15
The Voltage Divider with a Twist

• a 5V
• c 0V
• R1 4.7k ohms
• b (a-c)(4700/4700R2)
• 5(4700/4700R2)
• 3k lt R1 lt 11k claimed
• 300 lt R1 lt 500k actual

V
R1
R2
16
Photovore

• A photovore is a robot that is attracted to
  light.
• Grey Walter created the turtle robots in 1948
  it is unknown how they worked, but they were
  among the first photovores.

17
Photovore

• Braitenberg published a paper (1984) on a simple
  method of controlling a photovore.

18
Next weeks demo

• Your task to create a photovore
• Things to keep in mind
• Light levels vary depending on time of day
• Your photocells will NOT be identical, nor will
  they return the same values for similar light
  levels
• Hint you may want to compare both of your
  photocells for light intensity and drive in the
  direction of the greatest light intensity. Just a
  suggestion there are many ways to do this.

19
Photovores
20
A Quick Note about Breadboards
21
To Ffly C4
To Ffly C5