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INTRODUCTION. The aim of this application note is to provide a solid foun-dation for understanding and comparing the fundamental properties of speed sensors that are valid not only for Allegro products but for speed sensors in general.
- Review
- Today
- Voltage
- Current
- Parallel and series components
- Ohm’s law & power law
- Thevenin equivalent circuit
- Digital devices
- Input components
- Other input components in your kits
- Output components
- Optocouplers
- Summary
- Digital I/O
- Modeling analog devices
- Linear and Affine Models, Range
- Noise
- Mutex
- Time-triggered
- Digital to Analog Converter (DAC)
- Pulse Width Modulation (PWM)
- Digital Signal Processing (DSP)
- These things are not perfect
- Types of interrupts
- What if multiple interrupts happen?
- Interrupts can happen at any time
- Why do we care?
- Summary
Embedded systems are everywhere, have specific purposes, and unique challenges Microcontrollers (MCUs) have CPU, I/O, memory on one chip In lab you began working with an MCU and embedded hardware In homework you previewed sensors, actuators, I/O
⬢ Sensors and actuators ⬢ I/O ⬢ Interrupts “ Why would we as software engineers care about circuits, analog components, how I/O works, etc? Ideas
Difference in electric potential Measured between two points (or one point and implicit ground) We say we measure voltage across a component Voltage across resistor
Rate of flow of charged particles through a circuit Convention in circuits: imagine particles flowing from positive to negative terminal We say we measure current through a component Current through resistor
Series Current is the same through both components Voltage: ??? Parallel Voltage is the same across both components Current: ???
Ohm’s law: V = IR (SI units: volts, amperes, ohms) Power law: P = IV (SI units: watts, amperes, volts) Useful for: Computing values needed to build circuit Figuring out the limits of what you can attach to your microcontroller Writing down accurate math for modeling your system
Any linear electrical network containing current sources, voltage sources, and resistors can be replaced by an equivalent circuit with one voltage source and one resistor
Leds are digital output devices Things like push buttons are digital input devices (When connected correctly) are driven by or produce a high/low signal “ Can you give some examples of analog (produce/are driven by a continuous signal) peripherals?
Your book talks about: ⬢ Accelerometers (measure acceleration of displaced mass) ⬢ Anemometers (air flow for velocity) ⬢ GPS (satellite for position) ⬢ Gyroscopes (gimbals and modern) ⬢ Microphones ⬢ Engine controllers, thermometers, cameras, chemical sensors, etc
⬢ Photoresistor - resistance changes based on light ⬢ Potentiometer - outputs voltage based on rotation of the dial ⬢ Tilt sensor - Metal bearing completes circuit Image source
Your book talks about: ⬢ LEDs ⬢ Motors (DC) Your kits have: Image source ⬢ LCD screen (controlled digitally) ⬢ Servo motor (controlled by lengths of high/low pulses) ⬢ Piezo speaker (electricity displaces film to make sound) “ How do you control a DC motor that requires an external power source?
⬢ Control one circuit using another, but they are completely electrically separate! Image source Motor driven using mosfet and optocoupler
Laws of physics help us compute properties of circuits, for design, understanding, and modeling Devices can be driven/read with digital or analog signals, can be inputs (sensors) or outputs (actuators)
Microcontrollers are digital How do we read in analog input? How do we produce or simulate analog output?
Useful to have a mathematical model of sensors/actuators for verification and understanding
Map physical value at time t x(t) to sensor input Approximate with linear affine function, saturate if outside range [L,H]:
Error of measured value Comes from: Quantization Sensor imperfections What is the noise of our photoresistor?
Up to individual task to check for ADC to be free and then ask for sample
ADC runs in background and converts for all possible sources, storing the latest for each in a buffer “ What tradeoffs do you see between mutex and time-triggered ADC sharing? ADC sharing Mutex Time-triggered
Divide voltage based on digital number Actuator driven by DAC has similar quantization error to ADC Some MCUs don’t have DACs Expensive Fewer applications Unlike ADC, cannot share
Rapidly switch digital pin on and off Creates perception of analog output Increasing/decreasing duty cycle increases/decreases perception of power output level Many microcontrollers provide PWM peripherals Image source
ADC/DAC/PWM combined with computational power of an MCU has enabled the explosion of digital applications ⬢ Audio, video, robotics, medical... MCU lets you take in an analog signal, do computations on it, and produce a new analog signal DSP is a cool area but (mostly) beyond the scope of this course
Quantization, non-linearity, error in components all contribute to imprecision DSP can help alleviate some sources of error Design and models that take sources of error into account are vital for some applications
Software interrupts - function is called or some bits are set in a specific memory location to tell the software to go to an interrupt service routine (ISR) Hardware interrupts - external trigger (voltage change on pin) tells software to go to an ISR Exceptions - internal trigger (like writing to a protected memory location) triggers a fault
Often interrupts are prioritized Higher priority interrupt is allowed to interrupt lower priority interrupt Ties broken by position in vector interrupt table Programmer configures this when setting up code
Subroutine call: you know exactly when in the code you call it Interrupt: can happen at any point, even “inside” of a command Even x = x + 1 is made up of multiple machine instructions (load x from memory, increment x, write value back to memory) Atomic instructions: values being read/changed in atomic instruction cannot be read/changed by anyone e...
Physical devices (sensors and actuators) obey the laws of physics Can be controlled by digital or analog signals Can model this conversion using math Conversion between digital/analog: ADC, DAC, PWM Interrupts allow us to detect changes in inputs instead of just polling for them
Physical devices (sensors and actuators) obey the laws of physics Can be controlled by digital or analog signals Can model this conversion using math Conversion between digital/analog: ADC, DAC, PWM Interrupts allow us to detect changes in inputs instead of just polling for them
Searches related to define din speed sensor in computer science pdf
Sensors are required according to applications of different types of sensors such as: speed sensor for synchronizing the speed of multiple motors; temperature sensor used for controlling the temperature; ultrasonic sensor for measuring the distance, etc.
Revision notes on Sensors for the CIE IGCSE Computer Science syllabus, written by the Computer Science experts at Save My Exams.
Introduction to Robot Sensors. The three main pillars of robotic autonomy can broadly be characterized as perception, planning, and control (i.e. the “see, think, act” cycle).
Sensors are advanced devices that are often used to sense and react to electrical or optical signals. A sensor translates the physical characteristic into a signal which can be calculated electrically.
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Jan 1, 2023 · A sensor is defined as a device that receives a signal or stimulus and responds to it by generating an electrical signal. The output signals correspond to some forms of electrical signal, such as current or voltage, which can be easily measured.
