Digital Sensors, Analog Sensors, & Radio Frequency

Thanks for the amazing tutorial/breakdown on this stuff, Joe Saavedra!

An object that has an input (factor, interaction, pollutant, sensed thing) and an output (sound, light, data, kinetic movement, color).

Digital vs Analog
Analog Sensors

• Mercury Thermometer
• Button
• Any switch
• Potentiometers
• Analog
• Tilt switch — the ball rolls and happens to connect to poles to each other (conductivity of the balls on some wire)
• by themselves to not interpret or convert input into soft data

Digital

• http://en.wikipedia.org/wiki/Digital
• Require power (generally)
• Take analog (“real-world”) movement and converts it to a numerical value. That value is then passed digitally (1s and 0s) to something else (a microcontroller, computer, phone, etc)
  • This happens with a specific component called an Analog to Digital converter (ADC)
  • the Arduino has a 10-bit ADC. that means it can read discrete between 0 and 1023. (That is 1,024 = 1010 = 10 bits.  discrete values).
  • 1 bit is a ‘1’ or a ‘0’
  • “digital means ‘2’” — 0 or 1
  • 1-bit (101) can hold up to the number 2
  • 2-bit (102) can hold up to 4
  • 8-bit (108) can hold up to 256  ←- 8-bit color can be expressed in HEX (0-255)
• Microcontrollers (chips)
  • Tiny computers that have memory and programmable pins
  • Common Manufacturers:
  • Atmel (AVR)
    • Atmega328 (Arduino)
  • Microchip
    • PIC

Radio Frequency

• General RF Antennaes – transmitting data through high frequency radio waves
  • XBee
  • RFM-12B (22B)
  • RF Link

• RFID
  • 2 types: passive RFID (tag, sticker)
    • Tag = piece of memory, not a sensor
    • Reader = sensor – senses the tag, and reads data
  • active RFID (the reader — the security gates)
  • both are antennaes
  • RFID readers all need to be powered. They send out a signal and listen for a response. They vary in distance 2” – 20’.
  • RFID tags can be passive or active. stickers are all passive. they are an antennae (spiral looking) but at the center is actually a tiny piece of memory. the antenna resonates at a certain frequency (125MHz is what scigames uses), but there are several freqs. When it resonates, the memory (SUPER TINY AMOUNT. like enough to hold a single String of data (maybe 8 – 24 chars).
• NFC
  • a specific frequency of the RFID spectrum
  • 2-way communication. 2 active RFID readers
  • or a passive that can be read AND written to by an active

To learn about memory read about:

• Transistors
• Ray Kurzweil
• Moore’s Law
• Ubiquitous Computing
• M2M
• WiFi
• Bluetooth
• Serial data