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Lecture 4 - Sensors and Peripherals
- 2. Outline Sensors ◦ Button ◦ Potentiometer ◦ Light Sensor ◦ Temperature Sensor ◦ Distance ◦ Gas Sensor ◦ Digital Sensors Peripherals ◦ LED ◦ 7 Segment ◦ 74595 ◦ LCD Questions 2
- 4. Types 4 Analog ◦ Two pins ◦ There pins ◦ Use pin functions Digital ◦ Use some digital protocol ◦ Use libraries Two pins Three pins
- 7. 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/
- 9. 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
- 10. 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/
- 12. 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
- 13. Temperature Sensor LM35 Temperature Sensor 13 measuredV = pin 5 1023 Temperature = mesuredV *100
- 14. Gas Sensor Gas Sensor ◦ Heats up ◦ Three pins ◦ Vcc ◦ Signal ◦ Ground 14
- 15. 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
- 18. 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
- 20. 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
- 22. Microcontrollers and Computers MICROCONTROLLERS SPI ◦ Slave or master ◦ Hardware ◦ Software I2C ◦ Slave or master ◦ Hardware ◦ Software COMPUTERS SPI ◦ Master ◦ Hardware I2C ◦ Master ◦ Hardware 22
- 23. Peripherals 23
- 24. 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
- 25. 7 Segment Display Seven LEDS ◦ Common Cathode ◦ Common Anode ◦ Who many pins do we need for a digit? 25
- 26. 7 Segment Display Seven LEDS ◦ Common Cathode ◦ Common Anode ◦ Who many pins do we need for a digit? ◦ Multiplexing ◦ Microcontrollers 26
- 27. 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
- 28. 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
- 30. LCD LCD ◦ 16 pins ◦ Two data protocols ◦ 4 bit ◦ 8 bit ◦ Microcontroller ◦ I2C version (with an adapter) ◦ How many pins? 30
- 33. Questions? 33