Smart; Dumb Doorbell

With Rasberry Pi

Derek Carter aka "goozbach"

Goozbach Infrastructure Solutions LLC

how does a doorbell work?

• AC => AC transformer 120v to ~16v
• buttons close circuit
• electromagentic actuator hits chime

Hardware

• Raspberry Pi Zero W
• Some sort of relay board
• Doorbell chime with transformer
• Conduit box with plug

software

• RPi.GPIO library – managed GPIO pins from the Pi
• Urllib library – Send events to other URLs
• Flask library – Simply create REST interface

Wiring

• Connect chime to relay board
• Connect relay board to Pi GPIO pins
• Connect doorbell buttons to Pi GPIO pins
  • Be aware of lighted buttons (AC vs DC issues)
  • Add resistors!
    • “Pull Up”
    • “Pull Down”

Hardest part of this project?

Reading resistor codes

Step One – Ring the chime

• Create a REST interface which rings the chime.
• Wrap rest interface in testing HTML/AJAX

Step Two – Get button presses

• Event handler for buttton presses
• Don’t forget to wire properly
• Debouncing

Step Three – Connect button press events

• Use some sort of IoT like software
  • Pico-Engine
  • NodeRED
  • Lambda
• Going to leave this as an exercise for the reader

Lessons Learned

• It always takes longer than you think.
• Don’t put your GPIO ribbon cable on backwards
  • Female header is better (you can plug right into breakout board)
• Don’t over-torque your transformer’s plastic threads
• It’s hard to fit a USB plug, lightswitch, transformer leads and big wire nuts into a 2-gang conduit box
• 12Ga Solid copper wire WILL cut you!

Thank You!