Musical instrument tuning device

Claim 1

A drum tuning device for adjusting the tension on a drumhead comprising: a vibration sensor producing a sensor signal responsive to movement of said drumhead; a low-pass harmonic filter, connected to said vibration sensor to receive said sensor signal, said low-pass harmonic filter being adapted to pass a fundamental signal of said sensor signal; a compression amplifier connected to said low-pass harmonic filter, said compression amplifier being adapted to receive said fundamental signal and normalize said fundamental signal; a square wave amplifier-shaper connected to said compression amplifier to receive said normalized fundamental signal, said wave amplifier-shaper being adapted to convert said normalized filtered signal to a square wave signal; a pulse delay circuit, connected to said square wave amplifier-shaper to receive said square wave signal, said pulse delay circuit producing a reset pulse and a latch pulse timed with a portion of said square wave signal; a crystal controlled clock producing a plurality of clock pulses; a digital counter connected to said crystal controlled clock to receive said clock pulses, said digital counter being connected to said pulse delay circuit to receive said reset pulse, said digital counter being adapted to count said clock pulses and generate a counter signal, said digital counter being adapted periodically to be reset upon receiving said reset pulse; a plurality of latches connected to said digital counter, said plurality of latches being connected to said pulse delay circuit, said plurality of latches being adapted to receive said counter signal, said plurality of latches being adapted to store said counter signal upon receipt of said latch pulse from said pulse delay circuit, said plurality of latches producing a stored count signal; a diode matrix binary encoder producing a digital signal indicative of a frequency to be selected for tuning the drum; a first plurality of comparators, each comparator of said first plurality being connected to a latch, each comparator of said first plurality being connected to said diode matrix binary encoder, each comparator of said first plurality receiving a portion of said stored count signal from said latches, each comparator of said plurality receiving a portion of said digital signal from said diode matrix binary encoder; said first plurality of comparators producing a difference signal indicative of the difference between the stored count signal and the digital signal from said diode matrix binary encoder; a second comparator and digital-to-analog converter connected to said first plurality of comparators, said digital-to-analog converter producing an analog difference signal indicative of the difference between a plurality of low-order bits of said stored count signal and said digital signal from said diode matrix binary encoder; a level detector connected to said compression amplifier, said level detector also being connected to said first plurality of comparators, said level detector receiving a portion of said filtered signal from said low-pass harmonic filter, said level detector producing a level detector signal indicative of an amplitude of said filtered signal; a motor drive amplifier connected to said first plurality of comparators and said second comparator and digital-to-analog converter, said motor drive amplifier being responsive to said difference signal and said analog difference signal, said motor drive amplifier producing an amplified signal; and an electric motor-tachometer connected to said motor drive amplifier, said electric motor-tachometer being drivingly connected to said drumhead of said drum, said electric motor-tachometer being responsive to said level detector signal, said electric motor-tachometer being responsive to said amplifier signal, said electric motor-tachometer being adapted to adjust the tension of said drumhead to minimize said amplifier signal.