Garage Stereo II

An expensive but durable hands-free Bluetooth stereo for the garage.

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I first started building a cheap garage stereo when I got a Chinese-made amplifier intended for boat stereos. I built a stereo for my garage out of leftover car speakers hole-sawed into a hardware store plastic toolbox, and ran a line-in cable out of it in order to plug in any device.

My next step was to add wireless - after buying a cheap Bluetooth speaker on closeout from Best Buy, I dismantled it and transplanted the guts into my existing toolbox setup. Now I could connect to it from my phone and - while in range - control it and listen to music.

Now I want to add some logic to the toolbox stereo, so that I can mount buttons on it and interact with it instead of getting my phone greasy while working on a car. This will need a Bluetooth-compatible microcontroller that can understand A2DP for audio and the Bluetooth Audio/Video Remote Control Profile (AVRCP) so that I can control my phone from the playback device.

The intent of the project was always to spend as little money as possible. As such, many of the parts have been scammed out of friends' stockpiles of old car parts and assorted electronics junk.

Key scammed parts include:

  • The Chinese boat amp at the heart of the project - This is normally a $5 piece of junk from Amazon or eBay, but I managed to get one of these for free from a friend who was cleaning out his storage unit. That's what started this whole mess.
  • The low-profile, fanless PC ATX PSU that powers everything was pulled from a pile of junk destined for electronics recycling at my office.
  • All wiring comes from junkyard cars with expensive-looking aftermarket stereo installs, and was free (the you-pull-it junkyard I use doesn't bother charging for a meter of speaker wire if you're already there for more expensive parts).
  • The speakers come from friends who do expensive-looking aftermarket stereo installs, and were free. And they sound like it.
  • The plastic Skil toolbox which houses the unit was on Canadian Tire sale and was originally bought for a different project. Let's say it was free.
  • The Bluetooth speaker was on post-Christmas close-out sale at Best Buy for $5 and represents the only real money I've spent. Bonus: it has line-in, preserving the original implementation of the unit.
    • It also has a USB-rechargeable battery, the recharge port for which is hard wired into the PC ATX PSU. The battery is still there, but obviously the speaker is no longer fully cordless.
  • The first-gen Airport Express that used to power this was scrapped because the power supply had failed. After a little creative wiring, it ran off the PC ATX PSU just fine. It's remarkable that I haven't burned my house down yet.
  • I have two free Atmel microcontrollers that came in bags of leftover electronics parts from friends cleaning out their apartments; an atmega328p and an atmega168. Since I don't have any sockets or a programmer to use with them, these might be fairly limited in their applications.
  • I paid actual money for solder and butt connectors. But I didn't like doing it.

  • 1 × Chinese boat/car amp These things are all over Amazon. Just don't believe the wattage, because none of them are actually 500W. Hell, mine is lucky to have 5. Some of them even decode MP3 from SD cards.
  • 2 × 3.5" car speakers This is an uncommon size, especially if you want *speakers* and not just tweeters. Try looking in 80s German cars with small doors.
  • 1 × Plastic Skil toolbox on Canadian Tire closeout sale It doesn't have to be Skil. I just like to say it. Skil, skil, skil...
  • 1 × PC ATX PSU I found a low-profile fanless one but you can probably adapt any PC ATX PSU to serve this duty. Just short the green pin to ground and the PSU will always stay on while it's plugged in. You could also, you know, add a switch, but where's the fun in that?
  • 1 × Standalone Bluetooth speaker Just crack the case open. This one was held together with screws but others are held together with glue. You'd be surprised just how little is inside these things.

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  • How I would add a Teensy-LC to this mess

    Mike05/08/2015 at 03:06 0 comments

    This project needs a free Teensy-LC.


    • It's free. Look above and see why I like free stuff.
    • I've never had a teensy before.
    • It could help me build a programmer to flash the Atmel microcontrollers listed above.
    • If I came across a free Bluetooth serial module I'd be set.
    • It would be really nice to use to build an RF remote with.
    • 8KB should be enough for anyone.
    • It could drive a two-line character LCD to tell me what song is on.
    • According to the Teensy website it can drive a cool string of LEDs. People throw out LEDs all the time, and I would love to add blinky lights.

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