When learning to play a musical instrument to set the tempo often use a mechanical or electronic metronome. Last and I made one of the most popular modern developments. However, during operation it was found that this device is inferior to its mechanical counterpart, with adjustable pendulum, knob, jiggle measured which are perceived as the movement of the baton of the conductor.
Urgently had to make a new metronome with a visual indication. The resulting design was satisfied. And most importantly, such an electronic device was soon in demand by teachers, musicians for the planned lessons with the pupils, tutoring.
As can be seen from the circuit diagram, a part of my metronome includes tempo generator, generator indicator lights and warning sound. Food is the dry battery with a nominal voltage of 9 V.
Generator pace, made according to traditional canons on the timer DD1, produces rectangular pulses with a duty ratio close to 2. Timing RC-circuit it consists of resistors R1—R3 and capacitor C1. Variable resistor R2 changes the oscillator frequency rate in the range from 6 to 40 Hz.
The resulting signal output 3 DD1 fed to the input 14 of a decimal counter-divider on the chip DD2, which outputs (via current amplifier transistors VT1—VT10) loaded with LEDs HL1—HL10. At each IC output high DD1 level appears consistently. And only for the period of the clock pulse generator rate, and therefore the LEDs light up one after the other, creating the effect of “traveling wave”.
Simultaneously, the signal through a differentiating chain R4C3 is supplied from the output 11 of the chip DD2 to the input of transistor amplifier VT11—VT12 total load which is the dynamic head of BA1. R4C3 chain is used for shortening the rectangular pulse coming from the output 11 of the chip DD2, so that the loudspeaker you hear a click, similar to the countdown of the mechanical metronome. The frequency of the sound emitter can vary in the range of from 0.6 to 4 Hz resistor R2 generator pace.