Bluetooth Speaker

Recently I was given an old iPod dock for parts. Since I had some spare 3″ speaker drivers lying about, I decided to salvage the circuitry from the dock and make a portable speaker.

First, I had to make an enclosure. I used some scrap oak floorboards that I found in our shed, along with some pine for the front face.

I routed a step into the top of the sides, and joined them with a simple mitre. Then I cut and chamfered the speaker holes from the front face.

Next, I salvaged the amplifier PCB. It was the only part I needed from the iPod dock since the speaker drivers were cheap and very tinny. I added a bluetooth module, a battery management board, boost converter and a pair of Li-ion 18650s in parallel before testing the electronics.

Everything worked great, apart from the fact that I wanted to use a latching switch for power and a potentiometer to control the volume. This was a problem since the amplifier’s only controls were 3 momentary push buttons for power, volume up and volume down. Since the power button would only work when it was pushed and released, I had to come up with a way to simulate that happening, whilst using a latching power switch. In the end I used a relay, resistor and capacitor to create a circuit which simulated pressing the power button for half a second, then releasing it, then holding down the volume up button. This allowed me to control the volume of the amplifier by using a potentiometer at line level on the input.

When first turned on, the relay closes the power switch until the capacitor charges up. When it is charged, the power switch is opened and the volume up switch is closed. When the power is switched off, the capacitor discharges through a bleed resistor.

The electronics assembly inside are rather messy, and use copious amounts of hot glue, but it does the job.

The back has switchable inputs between a standard 3.5mm jack and a bluetooth module. There’s also a micro USB charging jack. 

Overall, I’m fairly pleased with how it turned out. The woodwork is pretty scrappy and could definitely be better, but it sounds pretty good 🙂