1. CBC Fundamentals
Lecture is based on material from Robotic Explorations: A Hands-on Introduction to Engineering, Fred Martin, Prentice Hall, 2001.

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CBC Features
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CBC Sensor Ports
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CBC Digital Input
47K for CBC digital port
15K for CBC analog port
WARNING: Mechanical switches BOUNCE!!!!!
A few milliseconds.
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Digital Function Call
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Analog Input
47K for CBC digital port
15K for CBC analog port
The 15K resistor can be disabled!!!
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Analog Signals
An analog voltage can take on any value between 0 and 3.3 Volts. An Analog-to-Digital Converter (ADC) within the CBC, however, will quantize the analog signal. The CBC’s ADC is 10 bits wide.
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Quantization
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Sampling Theorm
In order to avoid a non-linear phenomenon known as aliasing, an electrical signal must be sampled at a rate of at least TWICE the highest frequency component present in the signal.
Fs > 2 * Fh
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Complex Signals
Complex signals (like square waves) are actually linear combinations of sinusoids.
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Bandlimiting
Once a sampling rate has been determined, the input must be bandlimited. This means that the incoming electrical signal is filtered so that all frequency components above one-half the sampling frequency are removed!
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12. Analog Input Function Call
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Using Motors & Servos
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14. How do you connect motors to computers?
Computers operate at constant voltage and very low current
Motors draw high current and their speed and direction depends on the voltage
Robot controllers use:
H-Bridge circuit to handle current and direction
PWM to control speed
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15. H-Bridge - Separate Logic Current from Motor Current + + V - Pulse On
SF1
SR2 +
+ V -
Motor -
SR1
SF2
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16. H-Bridge (reversed) - Separate Logic Current from Motor Current +
Pulse On
SF1
SR2 +
- V +
Motor -
SR1
SF2
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17. Pulse Width Modulation
Pulse motor at fixed frequency
Maintains voltage level supplied to motor
Duty cycle governs speed
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Back EMF
XBC can measure EMF generated back from spinning motor
BEMF is proportional to actual motor speed
from acroname.com
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Wheel Encoders
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Servos
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CBC Servo Ports
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CBC Servo Ports
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