This project shows how to build a simple LED timer circuit using the popular 555 Timer IC set in Monostable Mode. This means the circuit will turn the LED ON for a set time when you press a button, then turn it OFF automatically. It’s great for projects that need a light or signal to stay on briefly after being triggered.
What is Monostable Mode?
The 555 Timer in Monostable Mode works like a one-shot timer:
- The output is OFF (LOW) until you press a button (trigger).
- When triggered, the output switches ON (HIGH) for a certain time controlled by a resistor and capacitor.
- After the set time, the output automatically goes back OFF and waits for the next trigger.
Components Required
- 555 timer IC ►https://amzn.to/3ubCBh1
- Resistors-10KΩ, 220Ω, & 8.2KΩ ►https://amzn.to/2QIeU2i
- Capacitor-220µF ►https://amzn.to/3woXsz9
- Push to on switch ►https://amzn.to/3veDxTk
- LED ►https://amzn.to/3oIS6fn
- 9v Battery ►https://amzn.to/2SlmSPe
- Battery clip
The Timing Formula
The ON time T(in seconds) of the LED is given by:
T=1.1×R×C
where
- R is in ohms (Ω)
- C is in farads (F)
You can change RR or CC to adjust how long the LED stays lit.
How It Works
- Build the circuit on a breadboard connecting the 555 Timer pins and timing parts correctly.
- When you press the push button, it triggers the timer, turning the LED ON.
- The capacitor charges through the resistor, timing how long the LED stays lit.
- When the capacitor voltage reaches about two-thirds of the supply voltage, the timer resets.
- The LED turns OFF, and the circuit waits for the next button press.
This simple electronic timer circuit is a perfect example of practical electronics and a great way to learn about the different configurations of the 555 Timer IC.
Watch the full video tutorial here: How to make an LED TIMER | 555 timer in monostable mode