In our family, we like to sleep with white noise. It drowns out the sound of the city outside (and the creaky floors if someone is up late). We like it so much that I installed two ceiling speakers in our bedroom just for playing white noise.
But I didn’t want to have to futz around with my phone or fiddle with audio electronics each night. And as it happens, our bedroom had one of those outlets that is turned on by a wall switch. This gave me an idea: could I make a simple relay device that would toggle an audio signal based on whether the outlet was switched on or off?
So I built this device. It’s just a two-pole 12v relay switch that toggles between two stereo audio signals from a pair of RCA connectors. The relay switch is connected to the wall outlet via a basic 12v power supply, and when the power is cut (via the wall light switch), the relay switches from one input to the other.
The finished device, hooked up. I've got an Airport Express (for AirPlay) on one input and an old iPod perpetually playing a 12 hour white noise loop on another.
Resources
Let me know if you successfully build this device yourself - I'd love to see it!
Outside the device, I’ve got a few things connected. First, I made a 12-hour track of white noise and copied it to an old iPod nano I had laying around. The iPod is connected to a charger so it never dies, and its output is connected to one of the toggle device’s inputs. The other input is connected to an Airport Express, so I can play music via AirPlay during the day. Finally, I bought a tiny power amp that is connected to the device’s outputs and to the speakers in my ceiling. Like the iPod, the amp stays on always. It doesn’t use much power.
And with that all set up, we’ve got a light switch that turns on white noise when you turn it off! I even had a spare plug in that switch-connected outlet, so it can switch a lamp at the same time.
Oh, and you might ask, “Why don’t you just plug the amp into the switch-connected outlet?”. Well, three reasons:
- the amp doesn’t handle depowering gracefully (you’ll hear a loud pop when it depowers)
- I wanted to be able to toggle between two audio signals, not just turn one on or off
- it was a fun project!
Let me know if you build this yourself!
