Saturday, July 25, 2015

LED Handbell Gloves

This project was quite long in development, more than a year, in fact! I learned a lot about technology design so the process is worth recounting. Two then-juniors I taught in a robotics class, Susannah and Nicki, now graduated, asked me for help with an idea they had. They were members of a handbell group they had played with for 5 years and wanted to make handbell gloves that light up each time they play a bell, unveiling the gloves for one piece in their final concert. We batted around some ideas. They thought about using a Lilypad Arduino and an accelerometer but I thought we
could accomplish the flash of light on each bell strike through simple circuitry.
We went through many iterations. The first used 4 LEDs and a 555 timer to sustain the LED flashes. It was overly complex, though fun to learn about the 555 timer. The second, represented in my poor sketch, had 4 LEDs, a capacitor, and a spring switch I adapted from the idea of the switch in light-up yoyos. LED yoyos only light up when spun hard enough. The mechanism that allows the circuit to close is a metal pole surrounded by a delicate spring. When the yoyo spins and spring bends and touches the pole, closing the circuit. I designed a similar mechanism that had a wire with a screw on the end and another wire that looped around the screw without touching it. The movement of the hand ringing the bell would cause the screw to touch the loop. The capacitor caused the LEDs to sustain their flash.

We tried making a custom PCB by designing this version in Fritzing and getting boards made at OSH Park. They didn't work! We gave up on that approach, deciding we didn't understand Fritzing well enough and didn't have time to learn. Unfortunately that meant we couldn't have 4 LEDs because the jumpers to connect them all would make soldering 10 boards too much work.
This is the next version, much simpler! After some testing we removed the capacitor because the quick flash was actually preferable to a sustained flash with the hands moving so much. This version has a bright white LED that is indeed bright when looking at it straight on.

We realized the bright white LED was barely visible when seen from the side so we replaced it with large, diffused LEDs, half white and half blue (for our school colors).

The big process discovery came when my students had soldered all 10 and hot glued them to the back of handbell gloves. They tried them out in a rehearsal and reported back that the lights barely worked.  It finally occurred to me that I had never actually watched them play! And they were players, not thinking like designers while they played. I went to watch them rehearse and it was clear that their hands moved about so much the spring switch wires got bent up right away, becoming unreliable as contacts.
My friend Steve Lewis had seen an earlier version and suggested using tilt switches, an idea I dismissed then, since the LEDs would light up even when they just reached for a bell. At this point the concert was less than a week away, so I figured swapping in tilt switches would be a more durable solution, if potentially inconsistent.
Here's the final version, and they ended up exceeding everyone's expectations.

The performance was a wonderful experience. They had the lights lowered, quite dark, and the lights appeared to me like fireflies, dancing in patterns that traced the melody of "Eye of the Tiger" in the dark air, making me feel like I was seeing the music as well as hearing it. The video I took of course cannot do justice to the experience, but it gives a sense of it.

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