[sdiy] The Story of the Theremin

[Paddock, Toby]

Michael Bacich wrote:
> 
> In a message dated 10/17/04 6:05:09 PM, tpaddock at seanet.com writes:
> 
> << Nope, I can't nail it on an accelerometer either.  :)
> I haven't heard the song lately, but I don't think it would help.
> 
> http://www.seanet.com/~tpaddock/public/g_vib.mp3 (230KB mono) >>
> 
> OK, that was funny.  However, I'm now feeling a little seasick.  Now you
> need
> to learn to play the theme from "Lassie".  Originally it was performed by
> somebody whistling, but a Theremin would be even cooler -- Kind of like
> "Lassie,
> come home... To MARS!"
> 
> BTW, I think you need a name for your gizmo.  I respectfully submit The
> Accelerometin  (or maybe The Acceleromotron).  Or, if you're an egomaniac
> (like
> me), you could call it The Tobytron...
> 
> Are you going to publish your design for all of us DIY geeks?
> 
> Michael Bacich

Oh yeah, an "accelerometin", I like it. I can't quite remember the Lassie
theme. Almost, but my brain keeps sliding off to the Andy Griffith show and
a part of Tubular Bells that I can't quite pin down. Need to find Lassie on
a tv theme website. 

There's not much to publish, It's just some Analog Devices accelerometers
and buffers. 9v battery, 5v regulator, a ADXL203 +/-2g 2 axis accel for the
2 horizontal axes, a ADXL105 (I think) +/-5g 1 axis accel for vertical, cmos
rail-rail quad opamp (TI TLV2474 I think) for buffers. 

Now it needs changeable gain and offset. The VCA is pretty happy with 0-5V,
but the VCF wants MORE RANGE!, and the VCO wants +/- instead of 0/+. And the
VCO really wants more range too sometimes for crazy noises.

Next time I'd use ADXL202 (like Harry did) for the horizontal axes because
it also has PWM output. I used the ADXL203 because I was helping someone
test a tilt sensor with them. 

For vertical, gravity is pulling a 1g offset and with a 2g part, that only
leaves 1g for shaking. Maybe that's OK for easy shaking.

Or for the vertical axis, maybe one half of a ADXL210 +/-10g and boost the
gain. 

Using 2 different parts means getting twice as many free samples  :)
And then get header boards for them at 
http://www.sparkfun.com/shop/index.php?shop=1&cart=107674&cat=71&
http://tinyurl.com/53eq2
who also have some interesting looking rf link modules.

There's some other choices
http://www.analog.com/en/subCat/0,2879,764%255F800%255F0%255F%255F0%255F,00.
html
http://tinyurl.com/3ogtk
What is a CP-16 package? Sounds too small for me.

I'm going to try mounting to a larger heavier thing to try to damp out the
coffee jitters.

Here's another quick sample with the 3 axes controlling VCO, VCF, and VCA of
a minimoog. Tilting and shaking only, no knob twisting. 

http://www.seanet.com/~tpaddock/public/accel1_128.mp3 (1.4MB 128kbps)
http://www.seanet.com/~tpaddock/public/accel1_48.mp3 (0.5MB 48kbps)

Toby