555 Timers - How a One Shot Timer Works
Karen has been digging into 555 timers for a bit now. In a previous video, she did an overview of the 3 different modes in which a 555 timer can be used. In this video, Karen goes into further detail about one of those modes: Monostable. Monostable mode is also known as a “one-shot” timer. In this mode, a single input signal of the 555 timer triggers it’s output to go high. The design of the rest of the external circuit will then cause the output to automatically reset back to low. Karen explains what’s happening inside the 555 to make this work, as well as showing a practical example of how to create this circuit on a breadboard.
Bill of Material:
| Product Name | Manufacturer | Quantity | Buy KitBuy Kit |
|---|---|---|---|
| Breadboard, MCM 60 rows, ABS, 8.5mm, 165mm x 56mm | Multicomp | 1 | Buy NowBuy Now |
| LM555CN - Timer, Oscillator & Pulse Generator IC, TTL Compatible, Astable, Monostable, 4.5 V to 16 V, DIP-8 | On Semiconductor | 1 | Buy NowBuy Now |
| Ceramic Disc Capacitor, 0.01 µF, 100 V, ± 20%, 5 mm | Vishay | 1 | Buy NowBuy Now |
| 140 Pc. Jumper Wire Kit, 22 AWG, Solid, Assorted Lengths and Colors | Twin Industries | 1 | Buy NowBuy Now |
| Through Hole Resistor, 220 ohm, 400 mW, ± 1% | Vishay | 1 | Buy NowBuy Now |
| Through Hole Resistor, 1 kohm, 500 mW, ± 1% | TT ELECTRONICS / WELWYN | 2 | Buy NowBuy Now |
| Red LED, Through Hole, 5mm, 20 mA, 2.1 V | LED TECHNOLOGY | 1 | Buy NowBuy Now |
| Tactile Switch, 12mm, Yellow, Top Actuated, Through Hole, Round Button, 24 VDC, 50mA | Omron | 1 | Buy NowBuy Now |
| Tactile Switch, 12mm, Red, 12 VDC, 50mA | Multicomp | 1 | Buy NowBuy Now |
Additional Parts:
| Product Name |
|---|
Desktop Power Supply |
Top Comments
One place where you’ll find this circuit is on a VIC-20 it uses a 555 to hold the reset line high during power on, before going low.