We didn’t get the lanterns finished on Wednesday, so we scheduled a finish-up work party for Saturday afternoon. We set up an assembly line and sent lantern parts down one by one: first Leah, Jordan, and Maja picked out color clusters and glued them onto the lantern bases, then Becky, Ellery, and I wired up the LEDs, then Richard, Mellington, and Barry soldered them together… with some switching of positions, and some coming and going, of course. We crunched through 34 of them before I had to leave, and the rest of the crew finished off the remaining six. Forty finished multicolored LED lanterns, with (mostly) waterproof cases and ground-stakes and switches and everything! So satisfying. They are bright and will make a beautiful, unusual accent for Barry & Maja’s wedding.

After soldering, I picked up Ava and we went to see Jerboa Dance perform “continuum”. Being a modern dance piece, I wasn’t actually expecting to understand it, and was astonished to find that it had a clear story arc with individual characters who developed relationships with each other of the course of the performance. All through motion and expression. Really well done, enjoyed it, would go see it again.

The PGA2310 / PGA2311 are 8-bit stereo volume control chips. They use a three-wire serial interface, and can make volume changes on zero crossings to eliminate clicks.

Three big boxes of parts arrived today: switches, resistors, and battery holders for the path lanterns, which we’ll build at the workshop on June 2nd; a couple of boards onto which I will build the bloom light controllers; and a pair of big plastic bowls which will serve as diffusers for the bloom lights. Not enough here to start actually building yet, but it’s fun watching it come together.

I’ve had a cold for the past couple of days. It’s mild, but I’m going camping this weekend out on John & Holly’s property in eastern Washington, and I’m not enthused about the idea of camping while ill. Oh, well, I’ll just have to rest and drink a lot of tea and hope for the best.

The Swinger is a little Python app that time-stretches an existing recording, adding shuffle to its rhythm. With examples: “Money for Nothing” and “Enter Sandman” are particularly awesome with a swing beat.

While browsing through Value Village’s collection of wall-warts looking for another 9V power supply, I happened to spot a Palm Portable Keyboard with a $5 sticker. Having randomly run across a description of the interface pins a few days before, I wasted no time snapping it up. It’s a great little unit: a full-size QWERTY layout, plus arrow keys and a handful of special-purpose function keys, and it folds up Transformer-style into its own little 3 1/2″ x 5″ carrying case. Now, what to do with it?

I’ve decided to run a little workshop evening for the LED lanterns. I’ll describe the circuit, explain how to extend it for other projects, then show how to assemble the device. We’ll build a few of them; I’m not sure how many we’ll make but I am guessing each person will be able to build a couple. This will be held on June 2nd. Location to be determined based on the number of responses. Let me know if you are interested in attending.

Instructable: how to assemble your own Arduino-compatible microcontroller board. It’s generally worth it to me to spend an extra $11 on one of Sparkfun’s Arduino Pro boards, but this is a really well laid out tutorial, and maybe I’ll want to build a whole lot of really cheap microcontroller-driven devices some day….

How to make round bacon, using a scary-sounding substance called transglutaminase, aka “meat glue.” With pictures.

More percussion circuits: these are nice and simple, and it looks like they will run on 9V, too.

Instructable about converting an ’82 Yamaha to run on electric power. 70 mph, 15-20 mile range, six moving parts including wheels.

Have I posted this before? From Roland’s ‘The Synthesizer’, Practical Synthesis for Electronic Music v2, Chapter 3: Rhythm and effects. It is a series of block diagrams for synthesis of standard percussion sounds using modular synthesizers.

Another interesting reference, albeit brief, is the block diagram for the Mungo dDS drum synthesizer. Clavia’s Nord Modular book has a chapter on percussion synthesis, with discussion that reminds me of the comprehensive Sound-on-Sound series [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11].

Circuit diagram for a synthesizer percussion module. It’s a basic ringing oscillator design, using trigger voltage as a pulse generator; it has an interesting adjustable-harmonics feature. It does not appear to be particularly adjustable; there’s no decay envelope or pitch control. Still, nice clear explanation.

This gadget works. It does exactly what I had imagined it would. The finish is a little rougher than I’d hoped for, but the functionality is spot on, and I’ll do a better job on the enclosure next time. It’s a lot of fun! I have it sitting on my music table plugged into the Electribe, and it happily thumps away, making completely plausible and often rather interesting percussion loops.

What to make next? Perhaps the walkie-textie.

A MIDI master sequencer keeps its slave devices synchronized by sending clock messages, 24 times per beat. The slave can use this to measure the current tempo, and might respond by playing some note, or by updating an internal timer used to drive arpeggiators or LFOs. If it is a sequence-oriented device, like a groovebox/drum machine, it will also use these clock messages to update its song pointer – the bar and beat it is currently playing.

The system works reasonably well, but it has one significant flaw: there is no provision for resynchronizing song pointers, and so the clock tends to drift over time. If an error occurs somewhere along the chain, and a clock message gets lost, all downstream devices remain out of alignment until the performance stops and starts again.

In general this is not a big problem. Errors are rare, and are not likely to cause perceptible drift in a 5-minute song. For people doing soundtracks, there’s a separate timecode system that provides absolute position. Further, many people do all their sequencing in software now, which solves the drift problem (and introduces many others, of course!).

My performance style, unfortunately, happens to live right in the sweet spot for this problem. My setup includes four tempo-synced devices, and I play continuously for 60-90 minutes, in a “thru-mixed” style which leaves few natural breaks where I could stop and restart the clock without creating an audible glitch. As a result, I run into synchronization problems in almost every performance. Sometimes I can work it out, but sometimes I just grind myself into a trainwreck.

Flush with success from my rhythm robot project, I’m thinking of building a custom MIDI clock device that will solve this problem for me. I imagine a straightforward black box with a big tempo knob, play/pause and stop buttons, a tap tempo button, and a “synchronize” button. Big LED readouts would advertise the current tempo and bar/beat song pointer. The back panel would have three or four parallel MIDI outs so I could run multiple slave chains, reducing latency.

But how to implement the synchronize button? MIDI does include a “set song pointer” message, but a sequencer is not supposed to send it while a performance is running – you’re supposed to pause first, set the position, then continue. Otherwise, maybe the slave device wouldn’t update itself quickly enough, and it’d miss a clock message! Oh no! … but how, exactly, is this any worse than staying out of sync? And this may have made sense thirty years ago, but I would be surprised if any of my modern gear has any trouble swallowing an extra message every now and then. Perhaps they ignore it, though; in that case, I’ll try sending a very quick pause/position/continue triplet. And if even THAT doesn’t work without causing a glitch, I’ll fall back on the fact that everything I do is aligned to groups of 4/8 bars, and the “synchronize” button will simply wait til the next 8-bar break, then send a “start” message, rolling everyone back to the beginning of the loop.

It should be pretty easy to test this out before I actually build the box. I’ll just rig up an arduino, a midi-out port, and a push button, and have it send clocks at some fixed rate, then see what happens when I send a song-position message.

I went to go ride my bike today, for the first time since the crash. This is the shiny new bike, which I chose specifically because I was tired of having to worry whether the machine would start; tired of having to be ready – at any time – to tinker with the machine until it was ready to go.

It doesn’t start.

Thank you very much, anonymous person who ran the stop sign.

The rhythm robot ought to be finished by now. I spent most of Sunday routing holes and fitting circuit boards, and the result is pretty sweet. I will really have to use a dremel tool next time instead of cutting all the holes by hand with an x-acto knife, though. I will also have to exercise a little more patience next time I try to de-solder the pins on my LCD unit; I ended up mangling the connector edge to the point of stripping copper traces off the PCB, and now the LCD is basically junk. Bummer. I hope to receive the replacement part tomorrow.

In the meantime, it looks pretty cool. I made little embossed labels for all the controls in red tape; it makes a delightfully retro contrast with the black case and silver knobs.

I ordered one of those cute old-school Dymo label embossers, to see if it would be a good way to make captions for the rhythm robot controls. Ava is having entirely too much fun with this device; the phrase “HEY, BABY.” just appeared on my monitor frame.

Git Sucks: a blog post by someone whose experiences with the New Hotness in version-control systems appear to have paralleled mine.

I spent yesterday evening working on the rhythm-robot, and have completed its main control panel. I am really happy to see it coming together. I have a clear image in my head of the instrument I want to play, and it feels good to see steady progress toward it.

Only after powering the board up did I discover I’d misread the datasheet for the PCF8574 port expanders: they’re advertised as having “latched outputs with high current drive capability for directly driving LEDs”, but this only works when you drive the pins LOW (logical false) – the chip can sink current but can’t source it. Of course I’d laid everything out the opposite way, since I want to turn the lights on by setting their pins HIGH (logical true)! Grr. Half a dozen NPN transistors solved the problem, but fitting the new components into the board and splicing them into the logic lines added almost two extra hours to the project.

Hevisaurus is a Finnish metal band whose members are all dinosaurs. They perform totally rocking tunes with a kid-friendly sensibility that is simultaneously adorable and awesome. Go Finland!