The electronics for this project are now available as a kit from Jameco electronics! Includes a blank PCB and all components/connectors required to build this project.
DISCLAIMER: Batteries can be dangerous. They can deliver high current if shorted out and start fires. If they are improperly charged it is possible they can explode. Please do not attempt anything that you are not familiar with and do not feel safe doing, and double-check your work. I am not responsible for any damage or injury due to misuse of these instructions.
Portable audio is a pain. Its either a huge boombox that eats D batteries like M&Ms, a bad-sounding iPod dock, or a virtually silent mini speaker set. None of these will do for a true music lover. Those who are so inclined and adequately skilled can build one that meets their exacting demands with relative ease. Now you'll be all set for a trip to the beach or camping.
A couple years ago while building an amplifier project I accidentally burned out the main driver from a set of Minimus 7 bookshelf speakers. Radioshack has sold this pair of speakers in various forms for over 30 years, and they are well known for their great sound and low price. I was quite bummed out that I was left with only one, collecting dust in my storage room, unlikely to ever be of use to me as a Hi-Fi speaker again.
Then I was inspired to turn it into a portable Hi-fi speaker by installing a rechargeable battery, charger circuit and amplifier. I had most of the parts needed lying around and managed to put the device together for only $15 additional costs. A thrifty shopper could probably do the project for around $60. Great value indeed!
In this guide, I will show you how I converted this speaker into a battery powered portable mini Hi-Fi system. It works great!
Step 1: Parts and Materials
- A bookshelf speaker. You're going to want something that will work well on only 10-20 watts of power, otherwise the battery life will be very, very short.
- Sealed Lead Acid battery. I know these are heavy, but they're also cheap and very easy to charge.
- Circuitry. The full bill of materials is on Step 3. The circuit is based on the reference design for a TDA2003 10 watt audio amplifier IC and a generic lead acid charging circuit using a LM317 variable voltage regulator, used to control charge current for the battery.
- 18V laptop power supply. It is important that it is 18V. The lead acid battery charger circuit needs 18V and the amplifier doesn't like continuous operation above 19V. Hopefully you can find one of these for cheap or free. 2A or more is plenty of current for this.
- Sheet metal. Something to fill the hole in the back of the cabinet to make a new control panel out of.
- 2.1mm DC input jack. For the input power from the laptop supply.
- 3.5mm stereo jack. For your audio source input.
- Toggle switches. For switching between wall power (charge) and battery power modes, and for on/off control.
- Potentiometer (optional). To control volume, if you want the ability to control it separately from your device. Controlling it from your device will save on your device's battery power, though. The TDA2003 only uses the power you hear so there is no waste of power having it at maximum volume all the time.
- Chip heatsinks. Definitely a good idea to add some small heatsinks for the ICs.
- Handle. Something to make it easy to carry.
- Rubber feet. To protect the wood and make sure the device doesn't slide away.