Patent Application
20100326258
The present invention relates to a strike input device for outputting a voltage representing a strength of a strike onto a striking pad, and more particularly to an electric circuit configuration of a strike input device for an electronic percussion musical instrument such as an electronic drum having a striking pad (i.e. music playing pad).
Known in the art are such electronic percussion musical instruments which have music playing manipulation devices in the form of pads (i.e. playing pads) to be struck by the player and generate electronic musical tones resembling drum sounds and cymbal sounds when the pads are struck, such as disclosed in examined Japanese patent publication No. H5-64463 and issued U.S. Pat. No. 4,932,303. When the player strikes the playing pad, the impact strength of the strike onto the pad is detected by an impact sensor such as a piezoelectric element or device. The impact sensor generates a vibrating voltage having a maximum amplitude which depends on the strength of the strike, which is a manipulation quantity of the player.
a shows a block diagrammatic configuration of a conventional percussion voicing device consisting of a drum pad circuit and a voicing unit, and
In the voicing unit 103, the drum pad output voltage input to the input terminal 104 is input to an envelope shaping circuit 105, which produces envelope signal representing an envelope shape of the vibrating voltage from the drum pad circuit 101. The envelope shaping circuit 105 includes a half-wave or full-wave rectifier circuit and an integrator circuit connected in cascade to output an envelope wave formed by bridging the peaks (crests) of the respective cycles of the rectified waveform one after another. The output from the envelope shaping circuit 105 is input to an A/D (analog-to-digital) converter 106, which samples the envelope wave by a predetermined sampling rate to produce a train of digital values representing the shape of the envelope wave digitally.
A central processing unit (CPU) 107 executes a computer program using a read only memory (ROM) or a random access memory (RAM), not shown though, and detects the maximum amplitude value of the envelope wave. Typically, the peak value (crest value) of the first cycle of the vibrating voltage which is generated by a single strike will make the maximum amplitude value among the decaying vibrating wave cycles caused by the single strike. It is simply because of easiness of the signal processing that the vibrating voltage wave is shaped into an envelope waveform, but the input vibrating voltage wave itself or a half-wave rectified or full-wave rectified wave of the input vibrating voltage wave may be input to the A/D converter 106. The CPU 107 digitally outputs in real time the maximum amplitude value as an output representing the magnitude of the strike force at the time point when the maximum amplitude is detected as a moment (time point) of the strike. For example, the CPU 107 outputs a note-on event message under the MIDI protocol containing the maximum amplitude value as a velocity value in the MIDI message. The CPU further drives a tone signal generator 108 to generate, at the moment of the strike, a percussion tone wave signal having an amplitude which corresponds to the maximum amplitude value of the vibration. The generated percussion tone wave signal which is a digital signal is then converted to an analog tone wave signal by a sound system 109 to be emitted from a loudspeaker as audible sound.
The drum pad circuit 101 shown in
The output of the A/D converter 106 in the voicing unit 103 is a digital value which is proportional to the input voltage at the input terminal 104 as depicted generally by a line segment 110b. More specifically, however, the A/D converter 106 will not increase its output value beyond its operating range where the input value exceeds its upper limit value (max), and keeps its maximum digital value as shown by a line segment 110c. Thus the increase in the input voltage will not be reflected as an increase in the output digital value. On the other hand, the A/D converter 106 outputs a zero value where the input value does not exceed its lower limit value (min), which is equal to one half of the resolution, and its digital “0” value is maintained within a certain dead zone 111 as shown by a line segment 110a. In the case of an A/D converter 106 with a limited number of coding bits, the amount of this lower limit input value (min) is not negligible. Therefore, in order for the voicing unit 103 to output digital values which increase faithfully in accordance with the input voltage, the input voltage (absolute value of instantaneous value) should be within the response range between the lower limit input value (min) and the upper limit input value (max). Where the operating range of the A/D converter 106 is narrow, the upper limit input value (max) cannot be high enough, and where the resolution is low (i.e. the number of coding bits is small), the lower limit input value (min) cannot be small enough, the response range will be narrow accordingly.
The problem in connection with the A/D converter 106 has been described above. In addition, there can be a problem that the voicing unit 103 may operate erroneously when the magnitude of the input voltage is small as compared with the noise level in the unit. Further, depending on a specific circuit configuration of the envelope shaping circuit 105, a small input voltage may not give an output due to the diodes included in the rectifying circuit, which means the envelope shaping circuit 105 also has a restriction of a lower limit input value (min). Still further, where the vibrating voltage is amplified through an amplifier, the amplifier may place a restriction of an upper limit input value (max) due to the saturation phenomenon of the amplifier.
Thus, in order for the voicing unit 103 to respond to any maximum amplitude values of the vibrating voltage, there is a restriction as to the input range of the maximum amplitude values of the vibrating voltage. To cope with such a restriction, it will be necessary to properly adjust or set the division ratio by the resistors 3 and 102 in the drum pad circuit 101 shown in
On the other hand, the division ratio by the resistors should be set rather high so that the maximum amplitude value of the vibrating voltage outputted from the drum pad circuit 101 should not fall within the dead zone 111 as shown in
In view of the foregoing circumstances, therefore, it is a primary object of the present invention to provide a strike input device for an electronic percussion instrument, in which the maximum amplitude values of the vibrating voltage outputted from the strike input device are kept within a adequate width of range in response to the strikes of a wide range of strength.
According to the present invention, the object is accomplished by providing a strike input device comprising: an impact sensor for generating a first vibrating voltage in response to a striking force; and a nonlinear circuit having a nonlinear input/output characteristic and outputting a second vibrating voltage in accordance with the first vibrating voltage input from the impact sensor, the second vibrating voltage being nonlinearly related to the first vibrating voltage, wherein the nonlinear input/output characteristic represents a first increase rate of the absolute value of the output voltage to the absolute value of the input voltage where the absolute value of the input voltage is in the lower range, a second increase rate of the absolute value of the output voltage to the absolute value of the input voltage where the absolute value of the input voltage is in the middle range, and a third increase rate of the absolute value of the output voltage to the absolute value of the input voltage where the absolute value of the input voltage is in the higher range, the first increase rate being greater than the second increase rate, the third increase rate being smaller than the second increase rate but not zero. Thus, the output voltage from the strike input device, i.e. the vibrating voltage outputted from the nonlinear circuit, has a magnitude which is equal to or close to the vibrating voltage generated by the impact sensor where the strength of the strike is in the weak range, while the vibrating voltage generated by the impact sensor is suppressed from increasing linearly where the strength of the strike is in the strong range. Consequently, the maximum amplitude value of the output vibrating voltage can be kept within a predetermined output range, for a wide range of strength of the strike.
With a voicing unit to which is input an output from a strike input device according to the present invention, the maximum amplitude value of a vibrating voltage needs to be within a predetermined input range so that the maximum amplitude value of the vibrating voltage can be adequately detected and responded. Therefore, conforming the predetermined output range for the maximum amplitude value of the vibrating voltage outputted from the strike input device according to the present invention with the above-mentioned predetermined input range of the subsequent voicing unit will enlarge the input range of the strength of strike acceptable by the voicing unit for detecting the maximum amplitude of the vibrating voltage and responding accordingly to generate percussion tones.
As modifications of the above-described configuration, the following input/output characteristics of the nonlinear circuit will be still advantageous as compared to the conventional configuration. A first modification would be that the nonlinear input/output characteristic represents a larger ratio of the increase in the absolute value of the output second vibrating voltage to the increase in the absolute value of the input first vibrating voltage where the absolute value of the input first vibrating voltage is in the small range than the ratio where the absolute value of the input first vibrating voltage is in the middle range, and a same ratio where the absolute value of the input first voltage vibrating voltage is in the large range as the ratio where the absolute value of the input first vibrating voltage is in the middle range. According to this modification, the maximum amplitude value of the output second vibrating voltage can be raised above a predetermined lower limit.
A second modification would be that the nonlinear input/output characteristic represents a smaller, but not zero, ratio of the increase in the absolute value of the output second vibrating voltage to the increase in the absolute value of the input first vibrating voltage, where the absolute value of the input first vibrating voltage is in the large range than the ratio where the absolute value of the input first vibrating voltage is in the middle range, and a same ratio where the absolute value of the input first voltage vibrating voltage is in the small range as the ratio where the absolute value of the input first vibrating voltage is in the middle range. According to this modification, the maximum amplitude value of the output second vibrating voltage can be suppressed below a predetermined upper limit, responding to the variation of the maximum amplitude voltage up to the strong strike range.
In an aspect of the present invention, the nonlinear input/output characteristic of the nonlinear circuit represents a first increase rate of the absolute value of the output voltage to the absolute value of the input voltage where the input voltage is lower than a first threshold voltage, a second increase rate of the absolute value of the output voltage to the absolute value of the input voltage where the input voltage is higher than the first threshold voltage and lower than a second threshold vantage, and a third increase rate of the absolute value of the output voltage to the absolute value of the input voltage where the input voltage is higher than the second threshold voltage, the first increase rate being greater than the second increase rate, the third increase rate being smaller than the second increase rate but not zero. Thus, the condition for the nonlinear input/output characteristic can be easily established.
In another aspect of the present invention, the nonlinear circuit is comprised of a series connection of a linear resistance circuit and a nonlinear resistance circuit, the output being taken across the nonlinear resistance circuit, wherein the nonlinear resistance circuit is comprised of a parallel connection of at least a first resistance circuit and a second resistance circuit, the first resistance circuit including two diodes connected in parallel in an opposite polarity to each other, the second resistance circuit including two Zener diodes connected in series in an opposite polarity to each other. Thus, the nonlinear input/output characteristic of the strike input device can be easily established, using only passive circuit components. The passive circuit components does not need a battery or an electric power supply.
According to the present invention, a strike input device is advantageous in that the dynamic range, i.e. the range between the weakest strike and the strongest strike, will be widened, keeping the maximum amplitude voltages outputted from the strike input device within a predetermined (requisite) range acceptable by the subsequent voicing unit. Accordingly, the subsequent voicing unit to which the output voltage from the strike input device according to the present invention can respond to weak strikes as well as to strong strikes discriminating the variation of strikes in the strong strike range. An electronic percussion musical instrument having a percussion voicing device to which a strike input device according to the present invention is applied can provide a wide range of musical expression in good accordance with the variation in the strength of the player's strikes. A voicing unit to which a strike input device according to the present invention is connected can be configured with an inexpensive A/D converter having a low (rough) resolution and a narrow operating range, and can still generate percussion tones accordingly responding to a wide range of strengths of the player's strikes as in the case of a voicing unit comprised of a quality A/D converter having a high (precise) resolution and a wide operating range.
The invention and its various embodiments can now be better understood by turning to the following detailed description of the preferred embodiments which are presented as illustrated examples of the invention defined in the claims. It is expressly understood that the invention as is defined by the claims may be broader than the illustrated embodiments described bellow.
For a better understanding of the present invention, and to show how the same may be practiced and will work, reference will now be made, by way of example, to the accompanying drawings, in which:
a is a block diagram showing the configuration of a conventional percussion voicing device including a voicing unit; and
b is a graph showing a response characteristic of the voicing unit.
The present invention will now be described in detail with reference to the drawings showing preferred embodiments thereof. It should, however, be understood that the illustrated embodiments are merely examples for the purpose of understanding the invention, and should not be taken as limiting the scope of the invention.
The nonlinear resultant resistance network 11 comprises a parallel connection of at least a first resistance circuitry (1) and a second resistance circuitry (2). The network 11 shown in
The second resistance circuitry (2) comprises at least two Zener diodes 8, 9 of a same characteristic connected in series in an opposite polarity to each other. The shown example further comprises a resistor 7 connected in series with the series connection of the Zener diodes 7, 8. A Zener diode (8, 9) is an element having a variable impedance characteristic, showing, in its forward current direction, a same characteristic as an ordinary diode, and showing, in its reverse current direction, a non conductive characteristic below the Zener voltage becoming abruptly conductive beyond the Zener voltage to exhibit an internal resistance of approximately zero. As the diodes 5, 6 are connected in parallel in an opposite polarity to each other, and the Zener diodes 8, 9 are connected in series in an opposite polarity to each other, the resultant resistance network presents a symmetrical characteristic for positive and negative swings of the vibrating voltage, so that the subsequent envelope shaping circuit 105 can detect the absolute value of the vibrating voltage both from a positive swing and from a negative swing.
In
Vpadout=(Vpiezo/R1)/(1/R1+1/R4) Eq.1
Within this low voltage range, the ratio “(1/R1)/(1/R1+1/R4),” which is the gradient alpha (α) in
A description will next be made about the range in which the absolute value of the output voltage Vpadout at the output terminal 12 exceeds the conduction voltage (1st threshold) of 0.6 volt of the diodes 5, 6, but remains below the conduction voltage (2nd threshold) Vz of the Zener diodes 8, 9. The output voltage Vpadout at the output terminal 12 will be expressed approximately by the following equation Eq.2 with respect to the output voltage Vpiezo from the piezoelectric element 2.
Vpadout=(Vpiezo/R1+0.6/R2)/(1/R1+1/R2+1/R4) Eq.2
As described above, the ratio of the increase in the absolute value of the output voltage Vpadout at the output terminal 12 (i.e. the output voltage from the nonlinear voltage dividing network) to the increase in the absolute value of the output voltage Vpiezo from the piezoelectric element 2 (i.e. the input voltage to the nonlinear voltage dividing network) is the ratio “(1/R1)/(1/R1+1/R2+1/R4),” which is the gradient beta (β) in
In the range where the absolute value of the output voltage Vpadout at the output terminal 12 exceed the conduction voltage (2nd threshold) Vz of the Zener diodes 8, 9, the output voltage Vpadout at the output terminal 12 will be expressed approximately by the following equation Eq.3 with respect to the output voltage Vpiezo from the piezoelectric element 2.
Vpadout=(Vpiezo/R1+0.6/R2+Vz/R3)/(1/R1+1/R2+1/R3+1/R4) Eq.3
Under this condition, the ratio of the increase in the absolute value of the output voltage Vpadout at the output terminal 12 (i.e. the output voltage from the nonlinear voltage dividing network) to the increase in the absolute value of the output voltage Vpiezo from the piezoelectric element 2 (i.e. the input voltage to the nonlinear voltage dividing network) is the ratio “(1/R1)/(1/R1+1/R2+1/R3+1/R4),” which is the gradient gamma (γ) in
In this range, i.e. where the absolute value of the output voltage at the output terminal 12 is above the second threshold value, the ratio of the increase in the absolute value of the output voltage at the output terminal 12 (i.e. the output voltage from the nonlinear voltage dividing network) to the increase in the absolute value of the output voltage from the piezoelectric element 2 (i.e. the input voltage to the nonlinear voltage dividing network) is smaller than in the range below the second threshold value. It should be noted, however, that this ratio should not be zero, so that the vibrating voltage should increase at any rate as the input voltage increases. Consequently, where the vibrating voltage generated by the piezoelectric element grows larger in the highest range, the drum pad circuit 1 delivers vibrating voltage growing at a compressed rate. Strictly speaking, the above-mentioned Vz is the Zener voltage plus the forward-direction resistance of the diode, as two Zener diodes 8, 9 are connected in series.
The output voltage of the piezoelectric element at the intersection of the characteristic line 21 of the drum pad circuit 1 of
Hereinbelow will be discussed the conventional drum pad circuit 101 shown in
RL=1/(1/R2+1/R4) Eq.4
then, the input/output characteristic is of the line 25 in
The output voltage of the piezoelectric element at the intersection of the characteristic line 25 of the drum pad circuit 101 of
If the drum pad circuit 1 of
This embodiment is different from the drum pad circuit 1 of
In the above description, the resistors 3 and 4 are fixed resistors. But the two resistors 3 and 4 may be replaced by a potentiometer with its sliding contact connected to the second resistance circuitry (2), the resistor 10 and the output terminal 12. The potentiometer will serve to adjust or vary the voltage division ratio to compensate the characteristic difference of the piezoelectric element or to cope with the characteristic difference of the voicing unit 103. Further, in the drum pad circuit 31 of
While, in the above description, drum pad circuits to be included in a music playing pad for an electronic percussion musical instrument are illustrated as embodiments of the strike input device according to the present invention. Alternatively, the present invention can be practiced in a music playing stick to strike another arbitrary member to detect the strikes. Where there are game machines and personal data assistants which utilize strike event signals as their control signal, in which strike operations applied to the control members are detected and utilized for the various controls. The strike input device according to the present invention can be used also in a strike detection circuit of such control members.
While several preferred embodiments have been described and illustrated in detail herein above with reference to the drawings, it should be understood that the illustrated embodiments are just for preferable examples, that the present invention may not necessarily be limited to the illustrated embodiments, and that the present invention can be practiced with various modifications, improvements and combinations without departing from the spirit of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-154011 | Jun 2009 | JP | national |
