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

Copyright Prentice Hall, 2001 CBC Features Copyright Prentice Hall, 2001

Copyright Prentice Hall, 2001 CBC Sensor Ports Copyright Prentice Hall, 2001

Copyright Prentice Hall, 2001 CBC Digital Input 47K for CBC digital port 15K for CBC analog port WARNING: Mechanical switches BOUNCE!!!!! A few milliseconds. Copyright Prentice Hall, 2001

Copyright Prentice Hall, 2001 Digital Function Call Copyright Prentice Hall, 2001

Copyright Prentice Hall, 2001 Analog Input 47K for CBC digital port 15K for CBC analog port The 15K resistor can be disabled!!! Copyright Prentice Hall, 2001

Copyright Prentice Hall, 2001 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. Copyright Prentice Hall, 2001

Copyright Prentice Hall, 2001 Quantization Copyright Prentice Hall, 2001

Copyright Prentice Hall, 2001 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 Copyright Prentice Hall, 2001

Copyright Prentice Hall, 2001 Complex Signals Complex signals (like square waves) are actually linear combinations of sinusoids. Copyright Prentice Hall, 2001

Copyright Prentice Hall, 2001 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! Copyright Prentice Hall, 2001

Analog Input Function Call Copyright Prentice Hall, 2001

Copyright Prentice Hall, 2001 Using Motors & Servos Copyright Prentice Hall, 2001

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 Copyright Prentice Hall, 2001

H-Bridge - Separate Logic Current from Motor Current + + V - Pulse On SF1 SR2 + + V - Motor - SR1 SF2 Copyright Prentice Hall, 2001

H-Bridge (reversed) - Separate Logic Current from Motor Current + Pulse On SF1 SR2 + - V + Motor - SR1 SF2 Copyright Prentice Hall, 2001

Pulse Width Modulation Pulse motor at fixed frequency Maintains voltage level supplied to motor Duty cycle governs speed Copyright Prentice Hall, 2001

Copyright Prentice Hall, 2001 Back EMF XBC can measure EMF generated back from spinning motor BEMF is proportional to actual motor speed from acroname.com Copyright Prentice Hall, 2001

Copyright Prentice Hall, 2001 Wheel Encoders Copyright Prentice Hall, 2001

Copyright Prentice Hall, 2001 Servos Copyright Prentice Hall, 2001

Copyright Prentice Hall, 2001 CBC Servo Ports Copyright Prentice Hall, 2001

Copyright Prentice Hall, 2001 CBC Servo Ports Copyright Prentice Hall, 2001