Lecture 3 - Input and Output Devices Flashcards
What are analog devices and how do they operate?
1) Smooth operator; it works in a continuous and flowing manner, the same way in which they deal with information
2) These devices operate using analog signals
3) To interact with them in a Raspberry Pi environment, they first have to be converted into digital signals through the use of an external ADC
What are digital devices and how do they operate?
1) Digital devices break everything into steps making them more precise and easy to manage
2) They operate by using digital signals which come through a built-in ADC
Input Devices
Hardware or an external device which is used to send information to a computer; allows users to communicate whether it is direct or indirect (communicating refers to the ability to input data or commands), they convert physical data/information into computer signals
What are examples of input devices?
Keyboards, mouse, microphone, etc
Output Devices
Opposite to an input device: sends out information/data (from a computer to a different device or user)
What are examples of output devices?
Screen, displays, printer, etc
What can be said about the solderless breadboard protortyping technique?
1) Non-permanant connection
2) Relatvely fragile
3) Most typical way to arrange systems
What can be said about the stripboard prototyping technique?
1) Each row is an electrical connection
2) Robust method of implementation
3) Can have things soldered to it for a permanant electrical/mechanical technique
What can be said about the printed circuit board prototyping technique?
1) Most complexe version
2) Designed specifically for a specific function (custom made)
What is soldering?
A process in which two or more metal items arre joined together by melting and then flowing a conductive metal between the joint; it is a technique used to form permanant mech/elect connections between components
Name all input devices that have been taught in this course
1) Push Button
2) Light Sensors
3) Temperature Sensors
4) Strain Gauges
5) Pressure Sensors
6) Sound Sensors
7) Distance Sensors
8) Accelerometer
9) Pi Camera
Name all output devices that have been taught in this course
1) LEDs
2) Buzzer/Beeper
3) LCDs (Liquid Crystal Display)
4) DC Motor
5) Stepper Motor
6) Servo Motor
Sound Sensors
(What is it and how it works)
1) Senses sound levels
2) Translates the amplitude of an sonor volume into an electrical voltage for sensing sound level
What is the role of the diaphragm in sound sensors?
Generates an electrical signal when it vibrates
Push Button
(What is it and how it works)
1) Used as an input device; tells the computer when it has been pressed
2) Acts as a switch; when pressed = the voltage matches on either side of the button
Light Sensors
(What is it and how it works)
1) Used to detect the amount of light striking it
2) LDR: Can be used as an analog light sensor
3) Resistance increases when light decreases
4) Resistance decreases when light increases
Temperature Sensors
(What is it and how it works)
1) Detect their surrounding environment’s temperature
2) There are two types of thermistors: NTC (Negative Temp Coefficient) and PTC (Positive Temp Coefficient)
3) NTC = Temp sensor/inrush current limiter
4) PTC = Protection against overcurrent conditions and resettable fuses
Strain Gauges
(What is it and how it works)
1) Measures electrical resistance changes in response to the strain applied on the device
2) Takes advantage of the electrical conductance’s dependance on the conductors’ geometry
What are the two non-neutral states of strain gauges?
1) Tension: Area narrows + resistance increases
2) Area thickens + resistance decreases
(Grid is patterned in such a way that there is a linear change and electrical resistances when strain is applied in a single specific direction)
What is the formula to calculate strain?
Strain = (change in dimension / original dimension) = (change in resistance / original resistance)
Pressure Sensors
(What is it and how it works)
1) Used to measure the amount of pressure applied
2) Produces output signals directly proportional to the amount of pressure applied
What is an Absolute Pressure Sensor?
Measures pressure relative to perfect vacuum
What is a Gauge Pressure Sensor?
Measures the pressure relative to atmospheric pressure
What is a Differential Pressure Sensor?
Measure the difference in between two pressures
What is a Sealed Pressure Sensor?
Measures pressure relative to a fixed pressure value
What are the 4 different types of pressure sensors?
1) Absolute Pressure Sensor
2) Gauge Pressure Sensor
3) Differential Pressure Sensor
4) Sealed Pressure Sensor
What are the different designs for these pressure sensors?
1) Piezoresisitive Strain Gauge
2) Capacitive
3) Electromagnetic
4) Piezoelectric
Define a piezoresisitive strain gauge design for pressure sensors
Uses piezoresisitve resistance changes as pressure deforms the material
Define a capacitive design for pressure sensors
Variable capacitor detects strain due to applied pressure; capacitance then decreases as the pressure deforms the diaphragm
Define a electromagnetic design for pressure sensors
Changes in inductance allows the measuring of the displacement of a diaphragm
Define a piezoelectric design for pressure sensors
Uses the piezoelectric effect in select materials where electric charge accumulates in certain solids in response to applied mechanical stress
Distance Sensors
(What is it and how it works)
1) Uses sound to determine the distance between the object and the sensor
2) Emit a sound waves at a frequency outside of the hearing range that reflect and are then received back by the sensor; the distance is calculated based on the time between the sending and the receiving signal (Time of flight)
Accelerometer
(What is it and how it works)
1) Detects changes in acceleration
2) Analog version: A variable voltage caused by applied acceleration is converted into an equivalent acceleration
Pi Camera
(What is it and how it works)
1) Takes high-definition pictures and videos
2) Camera Serial Interface (CSI)
3) Attaches itself with the use of a ribon cable to the CSI port on the raspberry pi
LEDs
(What is it and how it works)
1) Emits a narrow bandwidth of visible light (different wavelengths = different colors)
2) Two terminal devices: Cathode (Shorter probe/ notch = negative) and Anode (Longer probe = positive)
What is a diode?
A type of electronic component which allows current to flow in one direction only
Buzzer/Beeper
(What is it and how it works)
1) Audio-signaling device (can be one of three types: mechanical, electrical, or piezoelectric)
2) Piezo type: Piezo vibration within a molded case. Emits sound when an applied voltage causes the piece inside to vibrate
LCDs
(What is it and how it works)
1) Uses liquid crystal to produce a visible image
2) 16 character/line
3) 5 x 7 pixel matric for each individual character
DC Motor
(What is it and how it works)
1) Direct Current (DC) Motor
2) Two-wire (GND and power) continuous rotations motor
3) Speed is controlled by PWM (Pulse Width Modulation); limits the rotations compared to it’s default 100% (when it’s completely on)
Stepper Motor
(What is it and how it works)
1) Same as the DC motor with the difference being they move in discrete steps
2) Coils are organized in “phases” (groups); energizes each group in a sequence hence, rotation is done one step at a time
3) Computer controlled = Precise position/speed
Servo Motor
(What is it and how it works)
1) Rotary/linear actuator which allows the control of the following: position, velocity, acceleration
2) The motor is coupled to a sensor for position feedback
3) Limited to 180 degrees of movement
4) Angular positioning can be controlled with a coded signal in the form of a PWM wave
How can one get these devices to communicate with the Raspberry Pi?
“Straightforward” approach would be through binary words another approach would be PWM
What is an actuator?
An actuator is a mechanical or electronic device within a system that receives signals from a controller and converts them into physical action or movement, enabling the system to perform a specific task or achieve a desired output.
