One resistor and one capacitor set every timer in electronics
Press a button and an LED stays lit for about 1.1 seconds, set by one resistor and one capacitor. Swap the resistor to change it.
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
9 parts on a perfboard 16 × 28 holes, plus hookup wire.
| Qty | Part | Where to buy |
|---|---|---|
| 1 | Electrolytic Cap10uF C1 | Buy Electrolytic Cap on Amazon |
| 1 | Ceramic Cap10nF C2 | Buy Ceramic Cap on Amazon |
| 1 | Power Input (2-pin) J1 | |
| 1 | Screw Terminal 2P (5.08mm) J2 | |
| 1 | LED LED1 | Buy LED on Amazon |
| 1 | Resistor (axial)100k R1 | Buy Resistor (axial) on Amazon |
| 1 | Resistor (axial)10k R2 | Buy Resistor (axial) on Amazon |
| 1 | Resistor (axial)330 R3 | Buy Resistor (axial) on Amazon |
| 1 | DIP-8 U1 |
Check every pin against the datasheet of the exact part in your hands before wiring.
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Cut list
15 wires, 445 mm (17.5 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 | ||
|---|---|---|---|---|
| 6 | BlackTRIG L11 → J4 | L11 → J4 | 33mm | 10mm (90°) |
| 12 | BlackGND D3 → M3 | D3 → M3 | 33mm | Straight |
| 5 | BlueTIMING F11 → I15 | F11 → I15 | 23mm | 16mm (45°) |
| 11 | BlueVCC G13 → C16 | G13 → C16 | 28mm | 15mm (90°) |
| 4 | GreenTIMING G12 → E17 | G12 → E17 | 33mm | 8mm (90°), 20mm (90°) |
| 10 | GreenVCC G6 → H14 | G6 → H14 | 33mm | 8mm (90°) |
| 1 | RedCONT L15 → H16 | L15 → H16 | 23mm | 15mm (90°) |
| 13 | RedGND D5 → D13 | D5 → D13 | 30mm | Straight |
| 7 | RedTRIG M12 → E13 | M12 → E13 | 33mm | 25mm (90°) |
| 9 | WhiteVCC F7 → C5 | F7 → C5 | 23mm | 13mm (90°) |
| 3 | WhiteTIMING H11 → F17 | H11 → F17 | 30mm | 20mm (90°) |
| 15 | WhiteGND J17 → H26 | J17 → H26 | 38mm | 28mm (90°) |
| 8 | YellowVCC H7 → L7 | H7 → L7 | 20mm | Straight |
| 2 | YellowOUT H19 → F13 | H19 → F13 | 30mm | 20mm (90°) |
| 14 | YellowGND C14 → I18 | C14 → I18 | 35mm | 15mm (90°) |
About this build
Most timers in electronics come down to a resistor charging a capacitor. This board shows it with a 555 monostable: press the button and the LED lights for about 1.1 seconds.
The time is t = 1.1 x R x C. Here R is 100k and C is 10uF, so 1.1 x 100,000 x 0.00001 is 1.1 seconds. Swap the 100k for a 470k and the same pulse stretches to about 5 seconds.
The button connects off the board on a screw terminal, and a 10k resistor holds the trigger input high until you press it. A 330 ohm resistor sets the LED current, and a 10nF cap steadies the control input.
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