Saturday, November 19, 2016


It's cold out. Rainy also.

Good day to spend inside prop-making. Where I'm chasing down cold solder joints. Perhaps I need to scrub my PCB's before I start soldering on them. Or on the revised board (which I thought was complete until I thought of adding pins for a "talking" version), increase the annular rings on some of the critical pads.

No failure yet on any surface-mount component. But the hand soldering has thrown up two USB jack errors and even a couple of loose joints on the LEDs.

Oh, yeah. Talking. There's an Adafruit board that will trigger 10 consecutive (or random) sound files when a single pin is held low. Unfortunately they discontinued the version with an on-board power amp, which means I need to find space on the Holocron for two additional circuit boards. This, and even more ribbon cable, is so aesthetically displeasing I don't really feel like making this a standard option. After all, this is why I went through all the effort to make a single stand-alone board that combines charge management, USB hosting, and LED controller:

Also aesthetically displeasing is the sound. I experimented with the drivers I had lying around, and I needed to pump up to three watts into a quality driver before it could push its way out of the acrylic box and sound half-way decent. I've gone and ordered another of the surface mount transducers that failed me on the raygun project --

-- because anywhere else would create at the least a nasty shadow and possibly require a hole in the box as well. Besides, sound coming from a hole sounds like sound coming from a hole. It is a better effect if it sounds like the box itself is making the sound.

Pity I happen to know a little acoustics (and cabinet design). Because what this really calls for is a ported enclosure:

But that totally changes the look of the Holocron. And this is not a time to think outside the box. I've spent way too long refining on this particular box. It is time to brave the rain, visit the lasers and cut enough pieces to start shipping complete Holocron kits. (I have just enough to make one complete kit now, and I might assemble it myself just as a final check of the latest round of adjustments).

Or solder up the last of the current run of circuit boards. I stopped dead when I ran into odd USB behavior, but now I know what was going wrong and can fix it. I should probably solder up a complete "talking" Holocron before I order the version 1.1 boards, though. There's just barely space to put a couple more terminals for that...

(Oh, yeah; there's alternates. Best is go with Teensy and the Adafruit audio adaptor daughterboard for it. Skip USB hosting and in-place recharge and just put a string of Neopixels in for lighting. The Teensy does the heavy lifting of not just sound playback but DSP to equalize it. But that's costlier, still messy, takes up even more space, and requires I spend time programming.)

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