gamelan and electronics: relay complete

It works! After replacing the relays with ones that were more robust, everything is working every time.

I wasn’t expecting the new relays to be so loud–too loud for some applications.
But in a musical performance I wouldn’t think they’ll be very audible.
The box came out pretty sharp, and the box itself was only $2.00 at the thrift store.

I taped a breadboard and the arduino against the walls:


And here’s it running from max/msp (you can hear how loud the new components are):

gamelan and electronics: relay

For my gamelan and electronics piece, I wanted to use voltage controlled events that corresponding to what was going on with the pots. Since the slendro scale has 5 pitch classes, I decided to reduce the 12 drum triggers to 5 events and then I have another computer hooked up to 5 relays switching 120v outlets. This part of the piece seemed easy at first, but has quickly proved to be the most frustrating.

I first built a circuit as described on this post and it worked great. I soldered the circuit into a PCB and it was totally fine. The second worked great too. Then, on the third relay circuit, I tested the 5v side no problem, but then when I plugged the extension cord into the wall there was a small pop and tuft of smoke, and my mouse and keyboard on my laptop went completely dead–they had to replace the logic board at the mac store.

The controller I was using (making things) was dead on the output side, and feeling like I wanted to keep moving, I replaced it with an arduino. I think from now on I will only use arduino if for no other reason than the cost. The making things controller I have was $150 versus $30 for an arduino… and I was already feeling weird about dedicating a $150 controller to a single project, but at $30 I could see buying a controller for every project.

Restarting with a renewed fear of relay circuits, I decided to put all the relays on one circuit, but 5 relays were drawing too much power from the arduino and, though it worked for a little while, all the relays broke one after the other. Hooking up external power seemed to solved this, plus I shifted all the digital pins down two pins so that I am using 2-6 rather than 0-4 (I didn’t realize digital out 0 and 1 are serial outs and make relays click really loud) — and I hastily started putting the relay box together, only to find that a few of the relays were already broken again. (Broken relays don’t always act broken, I’m finding). Last night, I bought a new type of relay more like the one found on the post, and I’m hoping that will fix the problem. The relays I’ve been using are the ones they have a Radio Shack and are rated .5 amp at 120V… But the new ones I ordered are 8 amps at 240V. Maybe that will do it?

I look forward to re-posting with pictures of a finished, perfect relay box.

gamelan and electronics: pots

I’m working on a piece for electronics and Javanese gamelan in slendro. As a way to coordinate acoustical events and digital ones (without having to know what those might be) I decided to build a bonang barung out of PVC parts. I wanted to create a player situation that was nearly identical to sitting and playing bonang, so I decided to build 12 instruments that were each a drum trigger and independent sound source. I ordered 6 inch cleanout caps and female fittings and found an electronic surplus selling speakers that would fit inside.

Looking around at tiny amp designs, I tried putting together a basic LM386 circuit, and found that running my Max/Msp patch through it sounded pleasantly distorted and would provide a nice contrast to the cleaner, brighter gamelan sounds. LM386 chips don’t seem to handle polyphony very well, but for a single sampled pot they sound perfect–almost like Konono No. 1, or something. My first tests with a slendro arpeggiator and a big bass speaker are here. I put together all the amplifiers in a few days, and by the last 5 I reduced the circuit to a much smaller footprint by straddling the LM386 across power and ground and then bending pins 2,4, and 6 inward to their respective rails. Similarly, I found putting the big capacitor close to the LM386 allowed me to bend the excess wire sideways and solder it to the chip.

I spent a day filing off all the plastic burs and stamping on the PVC. I even filed down the square edges to round them off a little– they looked too militant or something at first. I then painted the pots matte black, only to discover I needed paint for plastic (it has a solvent in it and was really nasty). I sanded and repainted the pots shiny black and the playing surfaces shiny gold. They will look pretty impressive up on a bonang rack under stage lights.

To mount the speakers inside the pots, I glued lengths of extension cord that I had from building relay circuits that make up another part of the piece. I found that by cutting the cord so that it was barely larger that the inside circumference of the pots, I could hold the weight of a speaker with tension alone. After gluing them in, the mounting surfaces are totally solid.