I was thinking, what christmas present i can send a friend, which really annoys him.
It should automatically starts when he unpacks it, so an idea for a light-sensor came up.
So i collected some garbage and soldered around. The result is:
- 10 Watt active loudspeaker
- 12,6 V / 10 Ah li-ion cells from an old laptop
- Photodiode for light-detection
- WAV-Player with SD-Card (based on http://elm-chan.org/works/sd8p/report.html)
- Standby-Current: 7 µA for 8 seconds, then a few mA for a few ms to check for light, in a loop.
By using 1,5 hours sound from a 18-rated "sports-"movie, it should not only be annoying but also really bad embarrassing for him, when his parents hear that sound from his room
To switch it off, he has to press the power-button 200 times, so it takes a bit
The package is still on the way to him - When it arrives i'll keep you updated if we are still friends anymore...
How it was looking before:
Building Battery-Pack from old Laptop:
Connecting the amplifier with bypassed volume-pot:
Building Wav-Player and Light-Sensor logic:
Ready for shipping
Schematic, Source, HEX-Files....