Build Your Own Mini Metronome: Circuit Diagram (40-208 BPM)
This circuit diagram represents a functional metronome, offering a flexible tempo ranging from 40 to 208 beats per minute.
The device employs a linear scale and a compact design for convenient operation.
Circuit Diagram
Parts:
- P1 100k Linear Potentiometer
- R1 10k 1/2W Trimmer Cermet
- R2 10k 1/4W Resistor
- R3 330k 1/4W Resistor
- R4 50k 1/2W Trimmer Cermet
- R5 100k 1/4W Resistor
- R6, R7 1k 1/4W Resistor
- C1 1µF 63V Polyester Capacitor
- C2 10nF 63V Polyester Capacitor
- C3 47µF 25V Electrolytic Capacitor
- IC1 NE555 General Purpose Timer IC
- Q1, Q2 BC560 45V 100mA Low Noise High Gain PNP Transistors
- Q3 ZTX753 100V 2A PNP Transistor
- SW1 SPST Switch (Ganged with P1)
- SPK 8 Ohm 40mm Loudspeaker
- B1 12V Battery (MN21, GP23A or VR22 type)
IC1 NE555
The NE555 is a widely utilized integrated circuit, frequently employed as a timing circuit. This particular instance leverages its functionality to generate a stable and adjustable clock signal, facilitating precise tempo control within the metronome. Its general-purpose nature makes it suitable for a broad range of applications, including frequency generation and pulse width modulation.
Q1, Q2 BC560
The BC560 is a commonly found NPN transistor, distinguished by its low noise characteristics and high gain. Within this circuit, the two BC560 transistors, Q1 and Q2, serve as PNP transistors. They operate in a common-emitter configuration, contributing to the linear frequency operation dictated by the variation of the potentiometer P1. Their low noise performance ensures a clean and accurate timing signal, minimizing any potential interference.
Q3 ZTX753
The ZTX753 is a PNP transistor offering high voltage and current capabilities. In this circuit, the ZTX753 transistor acts as a PNP transistor. It is strategically incorporated to produce a louder auditory click, resembling the operation of traditional clockwork metronomes. Its robust specifications—100V and 2A—ensure sufficient power for the speaker, resulting in a noticeable and distinct sound.
Notes:
- Q1 & Q2 provide linear frequency operation of IC1 following P1 resistance variation.
- Q3 was added in order to obtain a louder click, similar to clockwork metronomes.
- 12V micro battery was used to obtain more output power and more compactness.
- Rotate P1 fully towards R2, then set R1 to obtain 40 beats per minute (compare with another metronome).
- Rotate P1 fully towards R3, then set R4 to obtain 208 beats per minute.
- Finally mark the entire scale with the usual metronome steps as following:
40 - 42 - 44 - 46 - 48 - 50 - 52 - 54 - 58 - 60 - 63 - 66 - 69 - 72 - 76 - 80 - 84 - 88 - 92 - 96 - 100 - 104 - 108 - 112 - 116 - 120 - 126 - 132 - 138 - 144 - 152 - 160 - 168 - 176 - 184 - 192 - 200 - 208.
circuit from http://www.redcircuits.com/