Sensors and Peripherals

Outline
Sensors
◦ Button
◦ Potentiometer
◦ Light Sensor
◦ Temperature Sensor
◦ Distance
◦ Gas Sensor
◦ Digital Sensors
Peripherals
◦ LED
◦ 7 Segment
◦ 74595
◦ LCD
Questions
2

Sensors
3
Image from http://energia.nu/rapid-prototyping-made-easy-with-the-grove-base-boosterpack-starter-kit-from-seeedstudio/

Types
4
Analog
◦ Two pins
◦ There pins
◦ Use pin functions
Digital
◦ Use some digital protocol
◦ Use libraries Two pins
Three pins

Measuring Analog
Voltage divider
We measure the voltage in Vout
We have errors
◦ Read many values and average them
5
Image from https://learn.sparkfun.com/tutorials/voltage-dividers/applications

Button
“Analog Sensor”
Resistance
◦ Infinite if released
◦ 0 if pressed
6

Button Debounce
When the button is pressed
◦ Signal is bouncing
◦ Fast reading results in 0s and 1s
Solutions
◦ Read more values and average them
◦ Use a trigger
7
Image from http://www.engscope.com/pic-example-codes/basic-io-button-debounce/

Potentiometer
Variable resistance
Connect the
◦ middle pin
◦ One Side pin
8

Potentiometer is a voltage divider
Variable resistance
Connect the three pins
◦ One side pin to Vcc
◦ The middle pin the analog
◦ One Side pin to the ground
9

Light Sensor
Photo Resistor
◦ 2 pins
◦ R inverse proportional with the light
Sensor
◦ Photo Resistor
◦ Voltage divider
◦ Three pins
10
Image from https://inventrom.wordpress.com/2014/11/27/the-thing-in-internet-of-things/

Photo Resistor
11
Image from https://inventrom.wordpress.com/2014/11/27/the-thing-in-internet-of-things/

Temperature Sensor
Thermistor
◦ Resistance
Parameters
◦ R25 resistance - 25 degrees
◦ B – constant
12
measuredV = pin
5
1023
TR =
5
measuredV
R
ratio =
1
B
ln( TR
25R
)
Temperature =
1
1
298
+ratio

Temperature Sensor LM35
Temperature Sensor
13
measuredV = pin
5
1023
Temperature = mesuredV *100

Gas Sensor
Gas Sensor
◦ Heats up
◦ Three pins
◦ Vcc
◦ Signal
◦ Ground
14

Distance Sensor
SRF04
◦ Ultrasonic
◦ Sends a pulse
◦ Real time system
◦ Works on microcontrollers
15
Image from http://www.robot-electronics.co.uk/htm/srf04tech.htm

Distance Sensor
Infrared
◦ Analog
◦ Measure voltage
16

Digital Sensors
Use protocols
◦ SPI
◦ I2C
17

SPI
Master / Slave
◦ One Master
◦ Several slaves
◦ Master always initiates communication
Wires
◦ MOSI – Master Out Slave In
◦ MISO – Master In Slave Out
◦ SCLK – SPI Clock
◦ SSn – Slave Select
Speeds
18

SPI
19
Image from http://dlnware.com/theory/SPI-Transfer-Modes

I2C
Master / Slave
◦ One or more masters
◦ Several slaves
◦ Master always initiates communication
◦ Each device has an address
Wires
◦ SDA – Serial Data Line
◦ SCL – Serial Clock Line
Speeds
◦ Standard 100 Kbit
◦ Up to 3.4 Mbit
20

I2C
21
Image from http://opencores.org/project,openmsp430,downloads

Microcontrollers and Computers
MICROCONTROLLERS
SPI
◦ Slave or master
◦ Hardware
◦ Software
I2C
◦ Slave or master
◦ Hardware
◦ Software
COMPUTERS
SPI
◦ Master
◦ Hardware
I2C
◦ Master
◦ Hardware
22

Peripherals
23

LED
LED
◦ Diode
◦ Two legs
◦ Anode (+)
◦ Cathode (-)
◦ Start lighting up if it has more than 0.6V
◦ Infinite resistance up to 0.6 V
◦ 0 resistance when it lights up
24

7 Segment Display
Seven LEDS
◦ Common Cathode
◦ Common Anode
◦ Who many pins do we need for a digit?
25

7 Segment Display
Seven LEDS
◦ Common Cathode
◦ Common Anode
◦ Who many pins do we need for a digit?
◦ Multiplexing
◦ Microcontrollers
26

Shift Register
Serial to Parallel Register
Pins are limited
◦ Use expanders
◦ Shift register
QA .. QH – data stored
OE – enable (if 0)
SEN – Serial input
SRCLK – Serial clock
RCLK – register clock (outputs)
SRCLR – clear
QH’ – shift output bit
27

Shift Register
Serial to Parallel Register
QA .. QH – data stored
OE – Output enable
SEN – Shift In
SRCLK – Shift clock
RCLK – Latch clock
SRCLR – clear
QH’ – Shift out
28

Shift Register
29
Image from http://makeyourownchip.tripod.com/74hc595.html

LCD
LCD
◦ 16 pins
◦ Two data protocols
◦ 4 bit
◦ 8 bit
◦ Microcontroller
◦ I2C version (with an adapter)
◦ How many pins?
30

Arduino
Firmata
31

Standard Firmata
Standard Firmata
https://pastebin.com/uVgsFvD0
32

Questions?
33