Having to choose between “too loud” and “too quiet” sucks. Unfortunately the Spotify web UI has an annoyingly short volume slider. Fortunately that’s easy to fix with a bookmarklet.
Drag this bookmarklet to your browser bookmark bar, and click on it to expand the volume slider. The code is pretty straightforward, it just changes the CSS slightly.
This small MP3 player is triggered when the ultrasound sensor notices someone nearby for a longer period of time (must be closer than 70cm for >0.9s). The hardware uses:
Arduino Uno R3 (archive.org) Seeed Studio Music Shield v1 (archive.org) and micro-SD card with a MP3 file (shop (archive.org)) HC-SR04 ultrasonic distance sensor (eg shop (archive.org), they’re cheap) Breadboard, speakers, jumper wires Optional: LED, 330 Ohm resistor (to show that it’s still running) I hacked the Music Shield to include risers for some of the pins.