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Project Help and Ideas » extending the Robotic Xylophone capabilities

December 01, 2010
by Hilarious
Hilarious's Avatar

Excellent project. The only thing it lacks is variation in volume of a note. By that simply put, a soft or hard note. To extend the project would it not be possible to create a stronger voltage to produce a stronger and louder note. A lesser voltage across the solenoid or a greater voltage would soften or harden the note. Then there's dampening the bars. Like a piano used peddles to clamp down on a string to give that string a clear note and the clamp is then released to sustain that note. Could you not incorporate a second set of solenoids mounted inside the bar mount, it would only require one side to be fitted so the top end of, what is now a screw, retainer be used to clamp the bar. As you pointed out in you nice video the bars need to be mounted so as not to restrict that bar from vibrating. Also I would suggest that felt be used to support the bars rather than rubber as rubber dampens the sound much quicker as it is a more dense material. Look at even the most modern instrument and they still use felt.

Keep up the good work and keep the idea's flowing Hilary

December 02, 2010
by hevans
(NerdKits Staff)

hevans's Avatar

Hi Hilarious,

The xylophone as built actually can vary the magnitude of the note. Since we are using a digital "on"/"off" idea to drive the coils from our MCU we can't necessarily vary the voltage we pump through the coils, but we can vary how long we leave the coil on for. The longer we leave it on the bigger the bang. There are limits to this since once the slug strikes the bar leaving the coil on for longer only serves to muffle the sound. And if you don't leave it on for long enough the slug wont strike the bar at all. In our test we could vary the duration of the "on" time from about 6 milliseconds to about 20 milliseconds which resulted in a pretty big volume variation. Taking advantage of this would only require changes in code, and I really hope somebody tries it =).

You are right that felt would probably be a better solution, but I doubt it would be a very different sound. The rubber washers are already so close to the modes they mostly serve to prevent the bar from rattling against the plastic spacer.

Thanks for your input, and I hope to hear more about your projects here on the forums!


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