This mini metronome gives a linear scaled output and 40 to 208 beats per minute.
Circuit Operation: 1- Q1 and Q2 transistors provide linear frequency variation of IC1 depending on the changes of P1 value. 2- Q3 amplifies the click sound output and gives louder beats. 3- To provide a higher output , a 12V micro battery is used. It also makes the circuitry more compact. 4- Rotate the P1 potentiometer fully towards R2, then set R1 to obtain 40 beats per minute by the help of another metronome.
| P1 | 100K Linear Pot |
| R1 | 10K 1/2 Watt Trimmer Cermet |
| R2 | 10K 1/4 Watt Resistor |
| R3 | 330K 1/4 Watt Resistor |
| R4 | 50K 1/2 Watt Trimmer Cermet |
| R5 | 100K 1/4 Watt Resistor |
| R6,R7 | 1K 1/4 Watt Resistor |
| C1 | 1uF 63V Polyester Capacitor |
| C2 | 10nF 63V Polyester Capacitor |
| IC1 | NE555 Timer/Oscillator IC |
| Q1,Q2 | BC560C PNP Transistor |
| Q3 | ZTX753 PNP Transistor |
| SW1 | SPST Switch |
| SPK | 8 Ohm 40mm Loudspeaker |
| B1 | 12V Battery (MN21, GP23A or VR22 type) |
Components List:
Read More Source: http://www.redcircuits.com/Page8.htm
