Got a request to build a sensory board and figured I’d share it here. It’s one of my few woodworking projects that needed to have a good fit and finish and I feel that it came out pretty nicely. It’s an assortment of fabric materials and touchable items that are good for children to explore for sensory experience. The board itself is a piece of cabinet grade maple ply, with a red oak banding. I went with rabbeted corners on the banding because I don’t quite trust my current setup for doing miteres, something in my saw is getting sloppy. Anyhow, I think it turned out not too bad.
I like to have some tunes on when I’m out riding and the way I’d been doing it was to squeeze a set of headphones under my helmet, run a cable down to my phone in my pocket, and control volume and track by pressing the side buttons through my jeans. Not the best solution, and often when wearing gloves it was next to impossible to tell where the buttons were.
My answer was to try out one of these ebay bluetooth modules. For around 7$ these things can pair with your phone to provide audio output as well as a way to hook up custom play/pause/back/next buttons. The version I got was called a XS-3868 but they all seem to be based on the OVC-3860 chipset. My idea was to stick one of these in a project box and hide it somewhere on the bike, then run wires up for a place to connect the headphones and come up with some sort of handlebar switches for changing tracks.
The schematic is nothing special, the only notes are that the regulator section was replaced with one of these modules. On ebay they can be had for under 2$ a piece and they just simplify voltage sourcing so much. Last time I ordered some I got a 10 pack 🙂 The other note is that some filtering had to be added to the switch inputs. The GPIOs on this board only draw about 40 microamps at 1.8v, it’s awfully easy to pick up stray voltage that’ll trip those once you have a cable attached of any length. So there are 1uf caps in parallel with 4.7k resistors close to the module to help filter out unwanted inputs.
So the schematic looks all well and good, and the module looks pretty, but they came together to make something much much uglier…
I did attempt an an etched PCB layout for this board but the fine pitch on the module made it very difficult to get it soldered down without shorts, so that was abandoned and instead the module was stood off from a piece of copper clad board and fly wired down to a set of pads that I cut out with a dremel. It started off crude, and got even worse when I realized that the extra filtering was required for the switches. Cramming those in was not easy.
But the project box hides all sins, and even the project box will be hidden under one of the bikes side covers, so that’s good enough for me.
For the control switches, I’ve taken the smallest die cast aluminum project box I could find and put three push button switches in it. I used two black zip ties pulled through holes in the rear of the box to attach it to the handle bars, it actually came out alot cleaner looking than I expected.
I also routed the audio connection under the tank to a spot that I could connect my headset to but I since it turns out that all of the controls work whether the headset is plugged into the phone or into the bluetooth module, so I’ll likely just leave them plugged into my phone. It’s audio quality is better anyhow, and it’ll reduce the chances of me ripping something off when I inevitably forget to disconnect before getting off the bike.