Thx Ken.  Correct me if I am wrong, but it sounds like it only detects
on/off, rather than impact strength.  I wasn't aware that the piezo's put
out that high of a voltage.  hmmmmm.........

It does give me some evidence that the piezo will do the job, however.  I
still want to try out the accelerometers, also.

Good stuff!

--Joe Jansen

pic microcontroller discussion list <PICLIST@MITVMA.MIT.EDU> wrote on
03/30/2004 10:20:36 PM:

> Joe Jansen wrote:
>
> > Thanks for any suggestions!!!!!
>
>
> Hi Joe,
>
> I still have my E-mu Systems Drumulator drum machine (I love the '80s!).
I
> never bought the pad programmer for it, but here is some information
that
> might be useful to you regarding their piezo interface:
>
>
>
> From E-mu Systems Drumulator Pad Programmer manual:
> ---------------------------------------------------
>
> {
> Pad Programmer - Theory of Operation - Revision of 2/27/84
> The Pad Programmer consists of four independent trigger sensors with
> appropriate
> circuitry, with a common housing and power supply.
> The power supply is a simple three terminal regulator +5V supply. The
input
> voltage is
> between 8 and 25 VDC and the current requirements are small enough
(around
> 40 mA
> when an LED is firing, less quiescently) that heat sinking is not
required.
> The plug in
> wall unit supplies nominally 10V DC, which is filtered and regulated.
> The sensor is a piezo-electric crystal mounted in a housing designed to
> transmit
> pressure from a vertical strike by a drumstick, and attenuate vibrations
> conducted by the
> housing. This assembly is glued together and tested at the factory.
Service
> on these
> assemblies will generally be by replacement, as repairs are difficult to
> accomplish and
> will frequently be unreliable.
> The sensor produces a substantial voltage spike (10 to 100+ volts),
which is
> loaded by a
> parallel capacitor and resistor, and rectified by a full wave bridge.
The
> resulting positive
> voltage is attenuated and applied to one terminal of a comparator. The
other
> terminal of
> the comparator is adjusted for the desired sensitivity threshold. The
trim
> range is set to
> stay within the common mode range of the comparator. Positive feedback
> around the
> comparator is provided to minimize marginal switching. The comparator
output
> triggers
> a one-shot which will both swallow any comparator oscillation or
multiple
> triggering, and
> provide sufficient pulse width for the LED amplifier and for the output
> trigger pulse. Both
> of these signals are buffered from the one-shot output.
> For information on adjusting the sensitivity trims, refer to the earlier
> section.
> }
>
>
> Best regards,
>
> Ken Pergola
>
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