Transistor Drum Sound Simulator
This project a transistor
drum sound simulator from 1989 is interesting
because there is no processor in sight - it's all done with
transistors. No software pseudo-random-noise generator...
...No, No, No - the real deal - Real noise from the junction of a diode
(one leg of transistor disconnected).
In fact the whole thing is transistor based from the noise generator,
envelop shaper and audio amplifiction.
The Drum sticks do not use accelerometers just an arrangement of
physical mechanics to detect the drum hits - could be the first "air
drum kit".
Executive Summary of the Transistor Drum Sound
Simulator
A portable drum sound simulator, especially suitable for carrying by
the user, includes a pair of drumsticks containing electrical switches
which are actuated by change in motion. The switches are connected to a
trigger circuit which initiates operation of a drum sound generator
every time a switch is closed. The drum sound signal after
amplification drives a loudspeaker. The circuits and loudspeaker are
all contained in a small portable case. In an alternative embodiment, a
radio receiver is included, whereby the simulator is selectively used
as an independent radio, an independent drum sound simulator, or
combining the radio signal with the operator produced drum signals.
This design relates generally to a drum sound simulator of the type
which electronically produces a drum-like sound each time a drumstick
connected to the simulator taps against a surface, and more
particularly to a drum sound simulator which is portable and operates
without need for an actual drum. Drum beats are part of most music,
from very primitive native music to sophisticated classical
compositions and drums are often played in solo passages as part of an
overall orchestral or modern music performance.
Electronic keyboards are now available which can produce sounds claimed
to be similar to every known type of instrument including classical
instruments and more popular devices. New sounds are synthesized. These
keyboards, while transportable and perhaps considered in a sense to be
portable because they can be readily moved, are not in constructions
which an individual would carry during a performance. The keyboards
presently available generally attempt to suggest a piano keyboard and
the operator or user thereof sits at a bench or chair as would a
performer at a paino. A prior art device is known in U.S. Pat. No.
2,655,071 wherein a drum sound is produced electronically whenever a
performer taps on a modified drum with his drumsticks to complete a
circuit between stick and drum. Because it is necessary to transport
both the drum and the associated electronics, this device is not
portable in the sense described, wherein the performer is completely
free of his surroundings and can produce drum sounds without need for a
drum, or as described more fully hereinafter, without need for a hard
surface. The keyboards do not include circuits for interaction with
other sound sources.
What is needed is a drum sound simulator which is entirely portable,
can be carried by the performer and allows both solo performance and
accompaniment of available audio musical sounds from broadcast or
recorded sources.
Figure 1 : Perspective
view of a portable drum transistor drum sound simulator
Figure 2 : Top
Sectional view of the transistor drum sound simulator through
2--2 
Figure 3 : Top
Sectional view of the transistor drum sound simulator through 3--3
Summary of the Transistor Drum Sound Simulator
Generally speaking, in accordance with the design, a portable drum
sound simulator, especially suitable for carrying by the performer
independently of its surroundings, is provided. This simulator
comprises a pair of drumsticks containing therein electrical switches
which are actuated by sudden change in motion or acceleration of the
drumsticks, as when the moving sticks strike against a surface or when
a person holding the sticks moves them and rapidly stops them or
reverses their direction of movement. The switches within the
drumsticks are connected to a trigger circuit which initiates operation
of a drum sound generator every time one or both of the switches in the
respective sticks is closed as described above. The drum sound signal
is inputted to an audio amplifier which drives a loudspeaker producing
an audible sound, similar to that produced by an actual drum. The
trigger circuit, drum sound generator, audio amplifier and loudspeaker
are all contained in a small enclosure or case which provides access to
an ON/OFF volume control knob and allows for connection by wires
between the drumsticks and the circuits within the enclosure. A battery
within the enclosure activates the circuits and makes the unit entirely
self-contained and completely portable.
In an alternative embodiment, a radio receiver is also included within
the enclosure, whereby it is possible to use the device as an
independent radio, an independent drum sound simulator as described
above, or a device which combines the radio signal with the operator
produced drum signals such that the operator can accompany on the
drums, by simulation, the music played on the radio. An externally
operated switch allows selection between these three modes.
Accordingly, it is an object of this design to provide an improved drum
sound simulator which is entirely portable and independent of its
surroundings, being carriable by the user in performance.
Another object of this design is to provide an improved drum simulator
which includes drumsticks similar to actual drumsticks and operates
without need for an actual drum.
A further object of this design is to provide an improved drum sound
simulator which serves as either a simulated drum, a radio, or a drum
accompanying a broadcast or recorded performance.
Still another object of this design is to provide an improved drum
simulator, where the action of drumsticks initiates the simulated drum
sounds.
Still other objects and advantages of the design will in part be
obvious and will in part be apparent from the specification.
The design accordingly comprises the features of construction,
combination of elements, and arrangement of parts which will be
exemplified in the constructions hereinafter set forth, and the scope
of the design will be indicated in the claims.
Description of the Transistor Drum Sound Simulator
With reference to the Figures, the drum sound simulator of this design
includes two drumsticks 12 connected to an enclosure or case 14 by
means of individual leads 16 or cords. The drumsticks 12 are similar in
size and appearance to authentic drumsticks. Each stick 12 comprises a
rigid plastic tube 18 with a soft plastic tip 20 to cover the striking
end of the stick. The soft plastic tip 20 extends from the striking end
22 approximately 25% of the total stick length. At the handle end of
the stick 12, a soft plastic end cap 24 restrains the lead or cord 16
where it exits from the stick.
The enclosure or case 14 includes a loudspeaker grill cover 26, an
ON/OFF switch combined with a volume control 28, and a pair of soft
plastic rings 30, where the cords 16 enter the enclosure 14 through
openings 32 in the enclosure 14.
Inside the enclosure 14 are a loudspeaker 34 mounted to output sound
through the grill 26, the ON/OFF/volume control 28 of a conventional
type including a partially visible knob, rheostat and built-in switch.
Also included within the enclosure 14 are a printed circuit board 35
for the electronic circuits of the drum sound simulator in accordance
with the design, and a battery 36 which powers the electronic circuits.
The enclosure 14 is in two halves, namely a front 38 and rear 40. A
belt clip 42 is fixedly attached to the rear half 40. This clip slips
over the belt of a person carrying the simulator in accordance with the
design so that the user's hands are entirely free for manipulation of
the drumsticks 12.
The dimensions of the enclosure 14 accommodate portability, and minimum
size is only limited by the electronic components which are available
for packaging in the enclosure. Thus, an enclosure 14 which is readily
held in the palm of the hand, can be produced. However, increased
battery holding capacity and a larger loudspeaker which enhances sound
quality, can be used in larger versions which are still entirely
portable in the sense that they can be attached to the body of the
user. For examples, the belt clip 42, as illustrated, or shoulder
straps, etc., which still leave the user's hands free to manipulate the
drum- sticks 12, can also be used. Also, an external handle or straps
(not shown) can be provided on the enclosure 14 or on a lightweight
carrying case for the enclosure to enable portability. When not
carried, the device is easily placed on any surface so that the user
may freely manipulate both drumsticks. As described hereinafter,
operation with a single drumstick is also inherent in the device. As is
conventional with portable radios, cassette players, hand and desk
calculators, etc. etc., the drum sound simulator in accordance with the
design can be adapted for use with an external source of power in
addition to its inherent electric capability provided by the internal
battery 36. Jacks (not shown) can be provided to allow use of earplugs
or earphones.
Figure 4 : Sectional
view of the drumstick taken along the line 4--4 of the
transistor drum sound simulator 
View larger image here.
Figure 5 : Sectional
view of the drumstick taken along the line 5--5 of the
transistor drum sound simulator
As best illustrated in FIGS. 4 and 5, an inertia switch 44 mounts
within the rigid tube 18 of each drumstick 12. The switch 44 includes
an electrically conductive metal shaft 46 mounted in a non-conductive
holder 48 and concentrically surrounded by a circular coil spring 50.
The spring 50 is mounted at one end 52 around a protruding portion 54
of the holder 48. The spring 50 is coiled concentrically with the shaft
46 and is suspended as a cantilever beam which allows the other or free
end 56 of the spring 50 to swing or oscillate about its fixed end 52 as
described more fully hereinafter. The resilience of the cantilevered
spring 50 depends on the spring wire from which it is fabricated and
the closeness of the turns. As illustrated, the turns are adjacent to
one another and are sufficiently stiff such that in a static state, the
switch spring 50 maintains a substantially uniform gap 58 between the
spring 50 and the shaft 46. The magnitude of the gap is determined by
the circumference of the protruding portion 54 of the holder
48.
The external cord 16 passes through the hollow tube 18 and is anchored
to the holder 48 by a metal wire tie 60. Two electrical wires 62, 63
extend from the cord 16. The wire 63 connects to a rear extension of
the metal shaft 46, whereas the wire 62 connects to the spring coil 50
by way of a hollow insulating tube 64. A rigid core 66 fills the soft
tip 20 and extends between the tip 20 and the tube 18 to provide a
basically rigid structure covered by the soft tip 20. A machine screw
68 fixedly connects the holder 48 to the core 66. The core 66 is a
press fit within the tube 18. In alternative embodiments, for examples,
adhesives may be used for this connection or a screw through the tube
18 can engage the core 66.
The spring 50 maintains its relationship with the metal shaft 46, that
is, spaced apart, so long as the stick 12 remains in a static condition
or is moving without acceleration or deceleration. When the stick 12 is
moved briskly, that is, stick motion is abruptly changed, for examples,
as in striking a surface as one would strike a drum in a conventional
manner, or in "striking" the air by abruptly interrupting motion in one
direction of the stick 12 with a motion in the opposite direction, the
switch 44 closes. In particular, with these sudden changes in motion,
the momentum of the spring causes the spring coils to separate slightly
resulting in an elastic deflection or swinging of the free end 56 of
the spring 50 toward the metal shaft 46. When the spring 50 and shaft
46 make contact, an electrical circuit is completed through the switch
44. Contact is maintained only momentarily before the spring 50 resumes
its original spaced apart position relative to the shaft 46, whereby
continuity of the switch is opened. Individual or successive strikes
with the stick 12 result in any number of momentary switch contacts as
desired by the user. Each drumstick 12 contains such a switch 44 to
which the circuits respond.
The spring 50 has a stiffness which prevents unintended drum sounds for
light motions such as simply picking up or carrying the sticks. Spring
stiffness also operates to damp spring oscillation and prevent output
of plural drum sounds for single drum "strokes".
Figure 6 : Functional
Block Diagram of
the transistor drum sound simulator
As illustrated in FIG. 6, the drumstick 12 in combination with its
internal switch 44, provides a trigger signal upon closing the switch
44. The trigger signal initiates operation of a drum sound generator 70
having an output which is shaped by a trigger and envelope shaping
circuit 72 and fed to an audio amplifier 74 whose output drives a
loudspeaker 34. Each closing of a switch 44 outputs a single drum sound
from the speaker 34. The switches 44 are electrically connected in
parallel.
Figure 7 : Circuit
Diagram of the transistor drum sound simulator
View larger image here.
FIG. 7 is a circuit for analog operation in performing the functions
illustrated in FIG. 6. This circuit includes the battery 36, outputting
a voltage identified as V.sub.cc at its positive terminal and with its
negative terminal connected to ground. Across the battery 36, with the
intervening ON/OFF switch 28, is filter capacitor C14. Also connected
to V.sub.cc are one end of a resistor R15, the emitter of PNP (or
P-type) transistor Q6, collector of NPN (or N-type) transistor Q5, and
one end of resistor R16. The other end of resistor R15 connects to the
base of the transistor Q6 and to one end of capacitor C7 and resistor
R14. The other ends of capacitor C7 and R14 are connected to the
collector of transistor Q7, having its emitter connected to ground. The
collector of transistor Q6 is connected to the base of transistor Q5
and to one end of capacitor C6, capacitor C5, and resistor R10. The
other end of capacitor C5 and resistor R10 are connected to ground and
the other end of capacitor C6 is connected to resistor R11. The other
end of resistor R11 is connected to the base of transistor Q7. Also
connected to the base of transistor Q7, are one end of resistor R13 and
capacitor C8, the other end of resistor 13 is grounded and the other
end of capacitor C8 connects to one end of resistor R12 and to a pair
of jacks 76 in parallel. The wires 62, 63 from the external cords 16
from the drumsticks 12 connect in parallel to the two sides of the
jacks 76. The other end of resistor 12 is grounded. The emitter of
transistor Q5 connects to the collector of transistor Q4 through
resistor R9 and the collector of transistor Q4 is connected to one end
of capacitor C9 which couples the drum sound signal to the audio
amplifier 74 as explained more fully hereinafter.
The emitter of transistor Q4 is grounded and the base of transistor Q4
connects to one end of resistor R5 by way of resistor R8 and capacitor
C3 in series. The other end of resistor R5 connects to one end of
resistor R16. The other end of resistor R16 connects to the positive
terminal of the battery 36. Resistor R6 connects to the collector of
transistor Q3 and at the other end to the junction between resistor R5
and capacitor C3. The emitter of transistor Q3 connects to ground by
way of resistor R7 and capacitor C4 in parallel.
The base of transistor Q3 connects to the collector of transistor Q2
and to one end of resistor R4. The other end of resistor R4 connects to
the positive terminal of the battery 36 through resistor R16. Resistor
R3 connects between the base of transistor Q3 and the base of
transistor Q2. Transistor Q2 has a grounded emitter. Transistor Q1 has
its base grounded and its emitter connected to the base of transistor
Q2 through capacitor C2 and resistor R2 in series. The emitter of
transistor Q1 connects through resistor R1 to one end of resistor R4
and the end of resistor R16 away from the positive terminal of battery
36. The collector of the transistor Q1 is floating, that is, not
connected.
Capacitor C1 connects between ground and the end of resistor R16 away
from the positive battery terminal as does a lead from the jack
terminal 76 to which the wires 63 from the drumsticks 12 are connected.
As previously stated, the jack terminal is also connected to one end of
capacitor C8.
The audio amplifier 74 is conventional in design and needs no further
description herein. It is coupled to the drum sound generator 70 by the
amplifier input capacitor C9 which connects between the transistor Q5
in an emitter follower circuit arrangement and the resistance in the
volume control 28. It should be noted that when the switch 44 in the
drumstick 12 closes, as described above by a change in motion, the
capacitor C8 becomes connected at one end to the positive voltage
V.sub.cc through resistor R16, the jack terminal 76, and leads 62, 63
which are shorted together by the closed switch 44. The other end of
capacitor C8 is connected to ground through resistor R13. Thus, when
the switch 44 in the drumstick 12 is momentarily closed, and it does
not matter whether one switch 44 or both is closed since they are in
parallel, the capacitor C8 charges momentarily to the voltage V.sub.cc
to trigger the circuits.
The transistor Q1 and components R1, C2, R2 comprise a white noise
generator. The white noise output of this generator is amplified by the
transistor circuits Q2, Q3, Q4 with the parallel arrangement of
resistor R7 and capacitor C4 forming a filter, limiting the frequency
spectrum outputted from the amplifiers. Frequencies above 6000 Hz are
substantially attenuated.
Figure 10 : Alternative Circuit
Diagram of the transistor drum sound simulator
When a drumstick 12 strikes a surface or has a sudden change in motion,
the switch 44 inside the stick 12 closes and capacitor C8 is
momentarily charged to voltage V.sub.cc. This causes a monostable
circuit constructed around transistors Q7 and Q6 to provide an audio
pulse output which is shaped by the R-C network C4, R7 to provide a
triangular waveform (FIG. 10). The shaped pulse is coupled from emitter
follower Q5 to the audio amplifier 74 by way of the amplifier input
capacitor C9. This triangularly shaped signal output, limited in
frequency by the high pass filter R7, C4, when further amplified in the
audio amplifier 74 produces a sound from the loudspeaker 34 which
simulates an actual drum. Each actuation of a switch 44 produces
another drum sound output. Pulse width in the range of 25 to 100
milliseconds provides an effective drum sound simulator with a
preference in the range of 50-60 milliseconds.
In alternative embodiments of a drum sound simulator in accordance with
the design, either or both components R7 and C4 may be variable by the
user such that the frequency content of the audio envelope is variable
to modify the quality of sound as is pleasing to the user. Any or all
of C5, C6, R11 and R12 may be variable by the user in order to change
the envelope shape and audible sound quality. In such an instance, one
or more tone quality knobs similar to the volume control would be
provided as needed on the enclosure 14 where accessible to the user, or
screwdriver adjustment may be made available. Variable resistors are
preferred over variable capacitors for economic reasons and because of
the public's general use and acceptance of such controls on many
electrical devices.
In a circuit which gives satisfactory performance, transistors Q1, Q2,
Q3, Q4, Q5, Q7, and Q8 are N-type 9014C. Transistors Q6 and Q10 are
P-type 9015C and 9012H, respectively. Transistor Q9 is N type 9012H. In
microfarads, capacitor C1 is 47, C2 equals 0.01, C3 equals 0.01, C4
equals 0.1, C5 equals 10, C6 equals 1, C7 equals 1000, C8 equals 0.04
and C9 equals 1. In ohms, R1 equals 1 meg, R2 equals 10K, R3 equals
330K, R4 equals 18K, R5 equals 8.2K, R6 equals 2.2K, R7 equals 20K, R8
equals 3.3K, R9 equals 5.6K, R10 equals 2.2K, R11 equals 470, R12
equals 8.2K, R13 equals 10K, R14 equals 1K, R15 equals 1K and R16
equals 220. Commercial quality and tolerances apply to these nominal
values.
As stated, audio amplifier 74 is conventional and requires no
description herein. Other audio amplifier circuits of conventional type
will be suitable to receive the output from coupling capacitor
C9.
It should be understood that in an alternative embodiment of a portable
drum sound simulator in accordance with the design, the analog circuits
70, 72 (FIG. 7) can be replaced by a digital synthesizer circuit (not
shown) wherein an actual drum sound waveform has been digitized with
respect to time in a conventional manner and the drum sound data is
stored at separate addresses in memory means, for example, a read only
memory. To obtain the digitized data for storage, the drum sound
waveform is essentially broken into small time intervals, and a numeric
value is assigned to each time interval, which value corresponds to the
amplitude of the waveform in that interval. These values are digitized
in binary format and stored. When the circuits are triggered by closing
the switch 44 in a drumstick 12, the data is read out of the memory
addresses in a desired sequence and the binary numbers at each memory
address, are converted in a digital to analog converter to an analog
signal which is applied to the input of the audio amplifier 74. The
data which is originally stored in the memory is preferably derived
from an actual drum sound. The elements for this digital sound
synthesizer may be mounted on the same printed circuit board 35 in the
enclosure 14.
Figure 8 : Alternative Circuit
Diagram of the transistor drum sound simulator
View larger image here.
In another alternative embodiment of a portable drum sound simulator in
accordance with the design, as shown in FIG. 8, a radio 80, less its
final audio amplification and loudspeaker stages, is combined with a
two-pole, three position, ganged mode selector switch 82. Poles 84, 85
of the switch 82 move in synchronism in a conventional manner to
selectively make connection with associated contacts a, b, and c of the
switch, as illustrated. The output 86 of the sound generator circuits
connects to contacts a and b associated with pole 84, whereas the
output of the radio 80 connects to contacts b and c associated with the
pole 85. The poles 84, 85 are connected in parallel to the input of the
audio amplifier 74 at the capacitor C9. Thus, when the poles 84, 85 are
at position a, the drum sound generator 70, 72 is connected to the
audio amplifier 74, whereas the radio output is blocked. With the poles
84, 85 at position b, the output 86 from the drum sound generator 70,
72 is inputted to the audio amplifier 74 along with the audio output
from the radio. Thus, a user of this simulator can accompany the radio
sounds with his own drumbeats. With the poles 84, 85 at position c, the
drum sound signal generator 70, 72 is blocked from the audio amplifier
74, but the radio output 88 is coupled to the audio amplifier 74 and
the user may listen to the radio without any self-generated
accompaniment.
The radio circuits, which may be either or both AM and FM, may be
incorporated on the printed circuit board 35 with addition of a
variable tuning capacitor in the enclosure 14 as is conventional in
such radios. The station frequency indicator, that is, a dial, may
appear in the enclosure panel 90, as shown in FIG. 1, with a tuning
knob similar to the volume control knob 28 also protruding from another
opening in the enclosure.
It should be apparent that in alternative embodiments in accordance
with the design, the drum sound generator circuits 70, 72 in FIG. 8,
can be replaced with a digital synthesizer operating on internally
stored data, as discussed above. The radio 80 may be replaced by an
audio cassette player which is accommodated into a modified enclosure
14. Digitized audio tapes are coming on the market and a player for
such tapes may be used where the radio 80 is indicated in FIG. 8.
Similarly, compact disk players of portable design may be used. All
combinations of circuits for drum sound generation with broadcast,
stored and recorded music reproduction may be combined in an
arrangement as indicated in FIG. 8, where the user can choose between
listening to recorded, stored or broadcast music, his own generated
drum sounds, or a combination of recorded, stored or broadcast music
and his own generated drum sounds.
Also, in alternative embodiments in accordance with the design, the
three-position ganged switch 82 (FIG. 8) may be replaced by a larger
switch including more contact positions and/or more poles so that many
more functions and combinations may be accommodated. For example, many
electronic keyboard instruments now on the market include synthesized
rhythm beats, which may be stored in digitized format, or analog. The
stored rhythms, for example, waltz, march, jitterbug, etc., can be
selectively reproduced audibly while at the same time, the user of the
instrument is playing the keyboard which is selectively set to produce
one of many instrument sounds. Such a stored rhythm capability can be
provided in the enclosure 14 whereby a user of the device can use the
drumsticks in conjunction with a prestored rhythm beat just as easily
as the radio sound, for example, may be selected for accompaniment as
described above. It should also be understood that, with an enlarged
switch capability, all of these sound producers may be available to the
user in multiple combinations or solo. Thus, the device can include the
AM radio, FM radio, stored rhythm capability, audio cassette
capability, compact disk capability, etc., etc. All such combinations
with the drum sound simulator are considered to fall within the scope
of the claimed design.
Figure 9 : Alternative drumstick
switch
View larger image here.
In an alternative embodiment of a drum sound simulator in accordance
with the design, the trigger switch illustrated in FIG. 9 may be used
to replace the trigger switch of FIG. 4. In FIG. 9, the components are
functionally the same. However, the coiled spring 50' is mounted within
a hollow metal tube 46' concentrically. The spring is suspended as a
cantilever such that changes in motion, that is, accelerations, cause
the free end of the spring 50' to swing. Whenever contact is made
between the spring 50' and the metal tube 46', a circuit which extends
through wire 62', 63' to cord 16' is completed. The insulating holder
48' is adapted to support the metal tube 46' and the switch spring 50'
in their concentric positions. Either switch 44, 44' can be used in
drumsticks 12.
Also in further alternative embodiments in accordance with the design,
the drumsticks can be replaced by other devices, for example, maracas,
wherein the pebbles or beans usually contained therein are replaced by
a suitably mounted switch 44, 44'. Thus, when the user shakes the
maracas, a drum sound is produced from the simulator. Also, the
switches 44, 44' can be adapted for attachment to the back of the
fingers on each hand of the user, such that the user may slap any
surface and produce drum sounds as one would play bongo drums or a
tom-tom.
Click here for more project
ideas.
Jump
from transistor drum sound
simulator
to
Best Microcontroller Projects Home Page.
 |
Don't
forget
to Sign Up for your
Microcontroller
Newsletter
With "Essential tips and techniques",
..."New Site Info" and more...
|
|
|
|
|
|
|
 |
Including a
free project :
How to drive
an LCD and 12key keypad using "Only
One 8 Bit Port"
with no
interface logic!...
(Works for any microcontroller)
This costs you : Nothing... 
Just fill out the form below and you'll get full C source code and
project schematic and description. |
|
490-9117
|
|
|
Blink
Del.icio.us
Digg
Furl
Google
Simpy
Spurl
Technorati
Y! MyWeb
