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This 4 in 1 design is for the Advanced
Builder, I have a new
Ultimate RS
Theremin for the Average
Builder
How Does the 4 in 1 Work?
First you build a
Limited RS Theremin board which is strictly for volume
control. The TLC555 is in the exact location as in the Unlimited RS
Theremin so converting an Unlimited into a volume control should be
straight forward. Added to the design is another TLO82 U5 which is
used to amplify the signal. This beefed up signal is used to trigger
the TLC555 U4 into outputting a very narrow pulse through LED-2.
A short burst of LED energy is picked up by the Solar Cell and creates
an average voltage in the 1 uf capacitor C22. If you were listening to
the circuit you would hear very few pulses per second at low
frequencies and many at the higher frequencies. This
average voltage is used to control the bias on transistor Q19, controlling
its on or off transition . Using the hand capacitance
generated pulse will give you up to a 12" window of working
volume control. This solar cell approach creates a larger control
window than can be achieved using a FET Transistor.
Note: On
the Limited Board used with this volume control, place an extra
100 pf capacitor in parallel with C2 & C8 to lower the oscillators
operating frequency to 700 Khz. This prevents the pitch and
volume oscillators from interfering with one another.
The Malibu Super-Bright yellow LED tip is positioned 3" from the
solar cell surface in a dark enclosure,
giving optimal spread of the beam.
The right side of the
schematic is an enhanced version of the original Optical Volume
Control. Build this on a separate generic circuit board. By itself this right side circuit could be used as a stand
alone optical volume control using normal room lighting. The ability to
reverse the direction of the volume control on hand approach is
accomplished by using the bias battery V2. The battery will last its normal shelf life, something like 10 years or more! The battery drain is
only a few micro-amps.
R27 is for bias balance.
When you flip the direction DPDT switch, you readjust the potentiometer,
turning it to the opposite side.
The 4 in 1 Volume Control Components
LED's
LED 1 Super Bright LED
Cat # 276-309
$1.49 USD
LED 2 Super Bright Yellow, I removed
it from the Malibu sun-powered yard light
below.
Do not unsolder the LED,
just solder your wires to the LED board.
Solar
Cell
Lowe's Hardware Store - I removed
it from a Malibu sun-powered yard light -
Model LZ1 D
$8.98 USD
Unscrew the extra hardware and solder on your own wire lengths. (cool
- you get a bonus of 2 new ni-cad batteries.)
Integrated Circuits
U5 = TLO82 - Dual OP Amp
Cat #
276-1715 $1.89
USD (use with the extra 8 pin IC socket)
U4 = TLC555 - Schmitt Trigger/Timer Cat #
276-1718 $1.69
USD (use with the extra 8 pin IC socket)
IC Socket
8 pin "Purchase 1 package
of 2" Cat #
276-1995 .59 USD
Transistors
Q19 = 2N2222 Radio Shack has a pack of 15 Cat #
276-1617 $2.49 USD
(you should test them to avoid grief)
Resistors
R22 = 100 ohm (brown - black - brown - gold)
R25, R28 = 1K ohm (brown - black - red
- gold)
R18 = 4.7K ohm (yellow - violet - red - gold)
R19, R20, R21, R24 = 10K ohms (brown - black - orange - gold)
R23, R26 = 100K ohm (brown - black - yellow - gold)
(The above resistors are found in the the
assorted pack 271-308)
R27 = 1 Meg ohm potentiometer Cat # 271-211
$2.79
USD
Capacitors
C19 = Ceramic .01 uf or 103 marking Cat #
272-1065 .99
USD
C20 = .022 uf Cat #
272-1070 .99
USD
C21 = .1 uf Ceramic capacitors .1 uf or 104 marking Cat #
272-0109 $2.49
USD "5
pack"
C22 = 1 uf Tantalum capacitors Cat
# 272-1434 $1.49 USD
C23 = 1 uf non-electrolytic Metalized-Film
Capacitor Cat #
272-1055 $1.49 USD
Switch = Double
Pole Double Throw Cat
# 275-626
$3.99
Any
easy flipping DPDT switch can be used.
Audio In/Out Cord
The J4 Audio Out works best when fed into
a amplifier with a higher input impedance.
I cut apart a 36" Shielded phono extension cable. Cat
# 420-2361 $2.99
USD
Battery = 1 - 1.5 volt AA.
Holder = Cat
# 270-401 .99
USD
Last Update 11/24/03
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