This article explain simple 555 Timer Monostable Multivibrator Circuit.
Circuit create one single pulse when trigger comes.
Time period depend on resistor and capacitor.
Circuit is easy to build.
And this circuit can run from 5V to 12V power supply.
Many people use it for delay, timer, reset pulse and for buzzer control.
Circuit Working:
Parts List:
| Item | Quantity |
|---|---|
| Resistors | |
| 1k | 2 |
| 10k | 1 |
| Capacitor | |
| Ceramic 10nF | 1 |
| Electrolytic 1000µF 25V | 1 |
| Semiconductors | |
| IC 555 Timer | 1 |
| Push Button | 1 |
| Any LED 5mm standard | 1 |
| Power Supply 5V to 12V DC | 1 |
The 555 timer stay normally in stable state.
Output pin 3 remain low.
When trigger pin 2 receive low pulse then the internal flip flop set.
Output goes high for fixed time.
Capacitor C1 connected to pin 6 and 7 start charging through resistor.
When capacitor voltage reach two third of supply then 555 reset automatically.
Output goes low again.
Circuit is ready for next trigger.
Only one pulse generate for each trigger.
Pulse width depend on values of R and C.
Formula with Calculation:
Below is the formula for Monostable Multivibrator:
The monostable time T = 1.1 × R × C
R is resistor between VCC and pins 6 and 7
C is capacitor from pins 6 and 7 to ground
If R = 1 kilo ohm and C = 1000 micro farad
T = 1.1 × 1000 × 0.001
T = 1.1 seconds approximately
This is the output pulse width.
Change R or C to change time.
How to Build:
To build a 555 Timer Monostable Multivibrator Circuit follow the below steps:
- Assemble all the parts as shown in circuit diagram.
- Pin 1 connect to ground.
- Pin 2 trigger connect to switch through 10k R1 resistor to ground.
- Pin 3 output connect to load through 1k R2 resistor and LED.
- Pin 4 reset connect to VCC so circuit always active.
- Pin 5 Control Voltage connect to one end of capacitor C1 and other end to GND
- Pin 6 threshold and pin 7 discharge join together with timing capacitor C2 to ground and timing resistor R3 to VCC.
- Pin 8 connect to VCC supply.
- This form complete monostable circuit.
Conclusion:
555 Timer Monostable Multivibrator Circuit is simple and useful.
It give fixed pulse when triggered.
Only few components are needed.
Time period is easy to calculate.
Anyone can build the circuit for many small projects.