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.


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