First stab at adding bluetooth

I had a go at adding Bluetooth support to the turned speaker I made using an RN-52. It wasn't clear from the datasheet what sort of output I could expect from the RN-52.  All it said was that it was differential.  I tried hooking up one side of the differential pair to the headphone-in of the speaker to get a better understanding.  It worked! (Kinda!)

While audio was playing (with about 12 ohms across the input to ground) it was fine but there were very large pops when sounds started and stopped.  I suspect (but I don't have a scope available to check) the module centres its signal on 1/2Vin but turns off the driver when it's not using it.  That results in a big step signal when it turns its signal on and off, causing a pop.

Thanks to a tip from the AskElectronics subreddit, I now plan to build the headphone out circuit from the datasheet and then find some way to mix that with the existing headphone in, if possible.

Turned purpleheart speaker

I made this turned speaker for my girlfriend's birthday.  It makes use of the boost converter described in my Instuctable.  It was a bit of rushed build so I didn't have time to take pictures but here are the specs:

• 5V input to boost converter from a USB connection, boosted to ~18V.
• That 18V goes as input to a 10+W amplifier module.
• The amp drives a 3" full-range driver for 100-20,000Hz output.
• It's all housed in a purpleheart case that I turned on the lathe.
• After drilling holes for the accessory ports, I filled around them with Sugru for a nice finish.  I also used Sugru to add some rubber feet.

I recently added a thick MDF base (not pictured) with an in-built battery compartment so that she can move it around with her laptop easily.

I'd planned to add a laser-cut grill to the front but, although I cut the grill, I didn't have time to make a lid to house it and then the wood shrank significantly after I turned it making it very difficult to add one at this stage.

Bluetooth is next on the list...

New Instructable: building a boost converter

I recently needed a 5V to 18V boost converter that could source 600mA. I wrote up the build as an Instructable.

Purpleheart bowl

Yesterday's turning project; a bowl in purpleheart. I was pretty pleased with the shape but unfortunately, it cracked slightly while I was finishing it.

Sycamore bowl

I'm pretty proud of the shape of this bowl that I turned from a piece of sycamore. The rim has a slight inward curve, which was a little challenging, and its foot helps it to sit up from the table.  I turned the rim using a very pointy spindle gouge to be able to get the angle, then switched to a stubby bowl gouge and scraper for further down.

500,000 downloads

My Battery Watcher app just hit 500,000 downloads.  The download rate has slowed down quite a lot recently as I've not had any time to devote to updating it but I'm still amazed that it was so successful!

Cherry bowl

Cherry bowl, a photo by fasaxc on Flickr.

Had a good time on the lathe yesterday. I turned this bowl from cherry. My first try at a decorative rim went quite well and I was pretty happy with the shape.

Unlike the previous two bowls that I attempted out of zebrawood, it neither smells bad (zebrawood smells like cheese), nor did it explode and go flying off the lathe!