Technical specs and building journal
The elements:
1) 1-lb scale from Staples
2)2 piezo strip sensors from Digikey, part #MSP1006-ND: sensor 1 is the more sensitive kind with the weighted
end, sensor 2 is the less sensitive kind. Piezo 1 has a wire stylus
attached to the head; piezo 2 is linked to indicator lever with
elastic.
3) 1/4" tall ridges made by folding masking tape
4) 1 servo attached to top disc with elastic strip, powered with
9V battery attached to 5V power regulator
5) BX 24 on mini breadboard, powered by 9-V battery w/5V power regulator
6) Speakers with built-in amplifier: Radioshack part # 40-1407 with
4 C batteries in one rigged C battery holder.
7) Super-bright white LED from All Electronics to light up Jello
through hole in center of turntable, mounted on turntable support.
Powering speakers
Speakers powered by batteries cannot be powered by adding all the
batteries together into one circuit. They use one set of batteries
as a ‘ground’ and another as power to create a negative
voltage. The battery case holding the 4 C batteries in the box actually
contains two separate battery circuits running into the amplifier.
The volume can be changed on any speaker by putting a potentiometer
between the signal and the amplifier. Do not put the pot between
the power source and the amplifier lest you set the pot on fire.
Seriously.
Powering servos
Servos burn out quickly when given too much current. My servo
takes 6V OR LESS. Remember this.
Code
The problem with using FreqOut is that it suspends all other chip
operations while it sends signals out. I put my FreqOut command
at the very end of my servo twitching subroutine, hoping that people
would be too distracted by the loud noise to notice that nothing
else would happen while the noise was sounding. Again, if I were
to do this again I might try to work out an alternative to FreqOut.
Jello
For experimentation, make Knox Gelatin with half the amount of water
and substitute salt for sugar, doubling the amount. This makes an
incredibly firm, almost sculptural material that can be used and
reused after being refrigerated.
For presentation, any sweet Jello will do – however, the densities
of the two gelatins will be different, and the Knox recipe is almost
twice as heavy as the same mass of ordinary Jello.
Plastic
For future reference, the pink plastic was from Canal Plastics.
The circle and square were purchased separately from their surplus
bins, but are both the color called Flourescent Light Pink. The
white plastic is from Industrial Plastics, and is Opal White.
I used a drill with a threader and a tap to make the screw holes,
and glued everything together with methyl chloride, which, BTW,
causes nerve damage if you get too much on your hands. Wear latex
gloves.
Organization
For sanity’s sake, I attached everything to the project box
with velcro so that it could be easily removed for programming/re-organizing/recycling
components. The sticky-back stuff from Staples is okay. Also: never
again buy the shrink tubing from Radioshack. It melts.
Sources
Sensors: www.digikey.com
Piezo Film Vibration Sensor part # MSP1006-nd
Plastic: Canal Plastics, Industrial Plastics (both on Bway)
Scale: Staples
Random:
www.sculpt.com for latex
and casting supplies
www.allelectronics.com
for LEDs and motors
Diagrams/Code
circuit
diagram
BX pin assignment
BX-24 code
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