A metronome you can see, and hear, from one 555
A metronome from one 555 timer: an LED flashes and a buzzer clicks on every beat, from about 36 to 206 beats a minute.
Free build sheet
The parts, every wire with its length and bend points, a bend guide, both sides of the board and checkboxes to track your progress. Print it or keep it open at the bench.
Open the build sheetWhat you need
11 parts on a perfboard 16 × 26 holes, plus hookup wire.
| Qty | Part | Where to buy |
|---|---|---|
| 1 | Ceramic Cap100nF C1 | Buy Ceramic Cap on Amazon |
| 1 | Electrolytic Cap10uF C2 | Buy Electrolytic Cap on Amazon |
| 1 | Ceramic Cap10nF C3 | Buy Ceramic Cap on Amazon |
| 1 | Power Input (2-pin) J1 | |
| 1 | LED LED1 | Buy LED on Amazon |
| 1 | Potentiometer Q1 | |
| 1 | Resistor (axial)22k R1 | Buy Resistor (axial) on Amazon |
| 1 | Resistor (axial)10k R2 | Buy Resistor (axial) on Amazon |
| 1 | Resistor (axial)1k R3 | Buy Resistor (axial) on Amazon |
| 1 | DIP-8 U1 | |
| 1 | Piezo Buzzer U2 |
Check every pin against the datasheet of the exact part in your hands before wiring.
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Cut list
18 wires, 517 mm (20.4 in) in total, in the order the build sheet cuts them. Wire numbers match the build sheet. Each length includes 5 mm per end to go through the hole.
| Wire | Colour and net | Length | ||
|---|---|---|---|---|
| 18 | BlackVCC E4 → C5 | E4 → C5 | 18mm | 10mm (90°) |
| 12 | BlackGND H19 → L18 | H19 → L18 | 23mm | 15mm (90°) |
| 6 | BlackBEAT H24 → G12 | H24 → G12 | 53mm | 10mm (90°), 41mm (90°) |
| 5 | BlueBEAT G23 → L23 | G23 → L23 | 23mm | Straight |
| 11 | BlueGND D13 → F19 | D13 → F19 | 30mm | 20mm (90°) |
| 17 | BlueVCC N7 → F5 | N7 → F5 | 35mm | 10mm (90°) |
| 10 | GreenGND B7 → E12 | B7 → E12 | 30mm | 18mm (90°) |
| 16 | GreenVCC E16 → E24 | E16 → E24 | 30mm | Straight |
| 4 | GreenTIMING G17 → F12 | G17 → F12 | 35mm | 10mm (90°), 23mm (90°) |
| 7 | RedDISCH D16 → F16 | D16 → F16 | 15mm | Straight |
| 1 | RedCONT L15 → I15 | L15 → I15 | 18mm | Straight |
| 13 | RedVCC O8 → O17 | O8 → O17 | 33mm | Straight |
| 3 | WhiteTIMING D20 → F18 | D20 → F18 | 17mm | Straight |
| 9 | WhiteGND G5 → D7 | G5 → D7 | 23mm | 13mm (90°) |
| 15 | WhiteVCC H12 → D15 | H12 → D15 | 28mm | 15mm (90°) |
| 2 | YellowTEMPO M12 → J8 | M12 → J8 | 28mm | 15mm (90°) |
| 14 | YellowVCC N16 → I13 | N16 → I13 | 30mm | 13mm (90°) |
| 8 | YellowDISCH C15 → K8 | C15 → K8 | 48mm | 23mm (90°) |
About this build
A metronome you can see and hear, from one 555 timer. The chip runs as an astable. A tempo pot and a 22k resistor set the gap between beats, and a 10k resistor and a 10uF cap set the beat itself.
On every beat the output drops low for a split second. That one output sinks both loads at once, a red LED through 1k and a piezo buzzer, so the light and the click land together. The knob covers about 36 to 206 beats a minute. At 120 that's two short flashes a second.
It runs on 9V on a 16 by 26 perfboard, input at the top and buzzer at the bottom.
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