Friday, September 29
Shadow

Designing a cool smart doorbell for my house

Introduction

Our doorbell’s button stuck in the pressed position and caused the electromagnets coils to melt. I decided to use this project as an opportunity to design my own door bell using off the shelf hardware for the electronic and custom wood / acrylic case. I was also looking at a small project to try resin coating wood in order to get some experience for my upcoming computer desk project.

Requirements:

  • Fit with the decor – approx 10” x 5” x 2”
  • Play a mp3 / wav file when the doorbell button is pressed
  • Include addressable led strips for lighting effects
  • Use off the shelf component for the electronics
  • Easy to program so my kids can help
  • Use existing wiring (2 wire power + 2 wire button)

Hardware

Raspberry PI 3b + Raspian OS

I wanted to use an old RPi 1 or 2 that I have lying around but I also needed to have a Wifi connection and not have to use a USB dongle. The RPi3 is overkill for this project but makes it easier to work with

WS2801B Led strip (60 leds / m)

I wanted fully addressable LEDs and have good experience with the WS2801X so far. I went for a 60leds/m strip as I wanted diffused led where you couldn’t make out each individual leds

ESP32 + WLED

I have a drawer full of ESP32 Node boards so this one was an easy pick. I also used WLED in the past and like the simplicity of it

12V – 5V DC-DC converter

The original doorbell was powered by 18Vac over a wire that is about 50′ long. In order to avoid issue with voltage drop and high-amp over such a small wire, I power the system with 12Vdc which is then switched down to 5Vdc locally. I used two converters to keep the audio / led systems separate

3W Audio amplifier

The Raspberry can only drive headphones so I added a 3-12V 2x3W strereo amplifier along with 2 x 4ohms 3W speakers

Case

I designed the case in inventor / Fusion 360 so I could easily make changes, extract outlines for laser cut and export to Fusion for wood milling CAM

Acrylic

I used 3mm black acrylic and 4mm clear acrylic for LED lightpipes

Wood

I used a 1/2″ plank of maple for the front panel. I milled the panel then coated it in epoxy for a clean durable finish. I only applied one coat as I didn’t deem a mirror-perfect was required for this project

LEDs

I cutted the led strip to length for the 4 sides and then proceed to join them using short lengths of bare wire. I made sure to connect the power of both ends in order to avoid the brightness dimming due to voltage drop. I double checked all connections and let the leds on for the night to ensure no premature failure as the led won’t be accessible once the epoxy coat is poured

Epoxy coating

I decided to use an epoxy coat to finish the wood on this project. This allowed me to try epoxy coating on a small scale project. The only downside of using the epoxy was that the wood panel, clear acrylic and acrylic backplate would be permanently joined thus preventing access to the led strip

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