[time-nuts] time-nuts Digest, Vol 69, Issue 30

Dave Baxter dave at uk-ar.co.uk
Wed Apr 14 03:51:53 EDT 2010

> I will try Joe's idea of using a doorbell buzzer to introduce 
> vibration.  
> It's not easy to generate 1KHz vibration without professional 
> (and heavy) equipment :)

Use a small loudspeaker (of the type found in small portable radios, or
old PC monitors) with as large a metal nut as practical (so you don't
distort the diaphram/cone) glued to the center of diaphram/cone.  Excite
with 1kHz (sig/gen/PC and small amp) and the frame will vibrate as well.
(Every action has an equal an oposite reaction, Newton's law's etc.)

Then, with a rod (knitting needle or similar) attached to the back of
the speaker, you can "inject" releaively repeatable vibrations exactly
where you want, while holding the rim of the speaker very lightly.

No EMI issues to cloud the results, unlike doorbell buzzers.

Works well for clicks and tap's too, where you can accurately control
the polarity of the "disturbance"!

Best Regards.

Dave B.

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