Precision Metronome & Pitch generator

Precision Frequency generator 1 to 999 Hz
Precision Metronome 1 to 999 beats per minute

Circuit Diagram:


Parts:
R1__________1M 1/4W Resistor
R2_________22K 1/4W Resistor
R3__________6K8 1/4W Resistor
R4__________4K7 1/4W Resistor
R5_________47K 1/4W Resistor
R6________100K 1/4W Resistor
R7_________39K 1/4W Resistor
R8_________12K 1/4W Resistor
C1_________47pF 63V Ceramic Capacitor
C2_______2-22pF 63V Ceramic Trimmer
C3________470pF 63V Ceramic Capacitor
C4_________10pF 63V Ceramic Capacitor
C5________100nF 63V Polyester Capacitor
C6________220nF 63V Polyester Capacitor
C7_________22µF 25V Electrolytic Capacitor
D1-D15___1N4148 75V 150mA Diodes
IC1________4060 14 stage ripple counter and oscillator IC
IC2________4082 Dual 4 input AND gate IC
IC3________4520 Dual binary up-counter IC
IC4________4518 Dual BCD up-counter IC
IC5________4046 Micropower Phase-locked Loop IC
IC6________4040 12 stage ripple counter IC
Q1________BC337 45V 800mA NPN Transistor
XTAL______2.4576 MHz Miniature quartz crystal
SW1__________BCD Miniature Thumbwheel Switch (units)
SW2__________BCD Miniature Thumbwheel Switch (tens)
SW3__________BCD Miniature Thumbwheel Switch (hundreds)
SW4_________SPST Slider Switch (On-off)
SW5_________SPDT Slider Switch (Metronome-Pitch)
SPKR_______8 Ohm, 50 mm. Loudspeaker
B1_________9V PP3 Battery
Clip for 9V PP3 Battery

Circuit operation:

CMos IC1 and IC2B quad AND gate form a 2.4576 MHz crystal oscillator plus a 2400 times divider. IC3A provides further division by 16, delivering a 64 Hz stable frequency square wave. This frequency is multiplied (by means of Phase Locked Loop IC5, double decade divider IC4 and IC3B 4 bit binary divider) by the number set by three miniature BCD thumbwheel switches SW1, SW2 and SW3: units, tens and hundreds respectively.

Connecting, by means of SW5, Q1 base to pin 2 of IC6, we obtain (after a 64 times division) the same frequency set by thumbwheel switches with quartz precision, and no need for a scale indicator.

Volume regulation of the pitch generator is obtained trimming resistor R5. In the same way, with SW5 set to metronome, the small speaker reproduces the frequency set by thumbwheel switches but divided by 3840, thus obtaining beats per minute ratio.