TEMPO CONTROL CIRCUIT IN AUTOMATIC PIANO

摘要

PURPOSE:To control accurately the tempo of playing dependent upon an automatic piano with a simple constitution by processing the reproducing modulation signal of a tape for piano coder in a Schmitt circuit, a feedback-controlled monostable multivibrator circuit, etc., to generate stable clocks according to the reproducing speed. CONSTITUTION:The reproducing modulation signal of a cassette tape for piano coder is received by photo coupler PC, etc., and has the waveform shaped by Schmitt circuit, SH, and monostable multivibrator OM is controlled by pulses generated at the rise time and the ball time of these shaped pulses. This multivibrator OM is feedback-controlled by feedback amplification circuit NF, and D pulses generated through resistance R and capacitor C have the duty controlled to 75% and become stable clock pulses according to the reproducing speed. Consequently, when the reproducing digital output of the tape is controlled by these clocks to drive automatically many pianos, the tempo of automatic piano playing can be accurately controlled with a simple constitution.