I picked up an old intercom from an antique mall in Austin for about $20. After about a day of thinking of what to do, I landed on installing a Raspberry Pi Zero with Amazon's Alexa voice service installed on it.
After opening it up, I found that the electronics were incredibly simple. The knob on the front was connected to a 2 position rotary switch. Lift the knob up and it would switch the speaker to a microphone. This is the sort of intercom that would sit on someone's desk.
I decided to wire the speaker to a 1/8 audio jack and the switch directly to the Raspberry Pi Zero GPIO pins.
There are two indicator LEDS (green for Alexa listening, red for Alexa responding). I wanted these to be as low profile as possible to keep the entire thing looking like it did when I bought it.
Raspberry Pi Zero wired up. The wiring is pretty simple, LEDs and switch into the GPIO. I modified the USB hub to a USB micro to keep the size to a minimum inside the case.
The USB Hub has both a WiFi card and a USB audio card attached (along with a small microphone).
Hot glue is your friend. The USB hub is mounted in the back of the unit and the microphone sits directly behind the speaker. Press the switch and speak towards the speaker and the microphone right behind it will start listening.
The RPi Zero is mounted on the side of the case.
Overall I'm extremely happy with how this build came together. It only took about a day to put it together and most of that time was spent messing around with the programming.
It even got some love from the Raspberry Pi Foundation.
NavaSpirit - Alexa Pi
Raspberry Pi + Alexa Voice Service
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